# Scissor Truss Permanent Bracing?



## DIYOkie (Jun 27, 2013)

Building a 22' x 42' rectangle house with 2 x 6 walls and scissor trusses. It's about as simple as it gets. 4 walls, roof, a simple box. 8/12 pitch. There is no designer or engineer involved in this project. And there are no permits or inspections where we are building.

We have 15 of our 21 trusses up. Using frieze blocks and spacers, toe nailing to the top plates and installing hurricane ties. We have 2x4 temporary bracing at top, 12' diagonals and straight pieces to keep everything tight and level as we go along. 

But I'm having a real problem getting a handle on the permanent bracing. There doesn't seem to be a lot of information on permanent bracing for trusses, and even less so with scissor trusses. 

What is a fella to do....?


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## Guap0_ (Dec 2, 2017)

Some pics might help. In the meantime, the following site offers other sites.


https://www.eng-tips.com/viewthread.cfm?qid=56213


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## DIYOkie (Jun 27, 2013)

Guap0_ said:


> Some pics might help. In the meantime, the following site offers other sites.
> 
> 
> https://www.eng-tips.com/viewthread.cfm?qid=56213


I'll get some pics up tomorrow, if not tonight. Thanks for the link.


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## Nealtw (Jun 22, 2017)

Hope fully you have space above the freeze blocks for venting. 
Your bottom cord is more than 10 ft so you need a catwalk, 1x4 or 2x4 nailed to the top of the about the center, end to end, do a layout, they hold the truss one layout. 
Don't but join them go one above the other to the next truss. Be careful to match the wall lay out exactly, you will appreciate it when dywalling.
Start at one end just do most of the house stop before you get to the other end.
You want about s 10, 12 ft 2x4 nailed high in the gable and low at the other end, You don't get much of an angle but that is how it is done. Make sure the gable is plumb before you nail the lower end. Plumb the other gable the same way and then finish the cat walk.
If you can't get it to stay plumb like this then on one side on top nail a 16 ft 2x4 from near the peak on an angle to over the outside checking the gable plumb at the same time.
When you sheet the other side it will be stable.
Engineers call for a 2x4 block between each rafter at the top on edge. watch the layout as you move along.
The drywall would like the same blocks 2 in the bottom peak flush with both side angles for backing. 


The blocks usually use up all the garbage 2x4 and 2x6 that is laying around from the rest of the build and often it is the stuff used for foundation work.


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## DIYOkie (Jun 27, 2013)

Here's a couple of pics. Don't laugh at my ******* ladder contraption, it is a sturdy platform and the ladder is screwed down. Seems to work great. 










https://www.diychatroom.com/members...net-rd/36015-resized-20181028-155715-9705.jpg


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## Bud9051 (Nov 11, 2015)

So you built your own scissor type framing, not pre-made trusses and as Neal suspected it looks like your blocking is blocking all potential air flow from the soffit area. Not slamming you and it is much better to get the input now than later.

If you are using 5/8" sheathing, once in place it will add a lot of stability, but be sure everything is perfectly squared up.

Bud


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## Nealtw (Jun 22, 2017)

Take the freeze blocks out, there is no need for them.


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## DIYOkie (Jun 27, 2013)

Bud9051 said:


> So you built your own scissor type framing, not pre-made trusses and as Neal suspected it looks like your blocking is blocking all potential air flow from the soffit area. Not slamming you and it is much better to get the input now than later.
> 
> If you are using 5/8" sheathing, once in place it will add a lot of stability, but be sure everything is perfectly squared up.
> 
> Bud


No, no, those are pre-made trusses. I don't know enough about engineering to pull off truss design and build. 

Our approach on the frieze blocks was to drill them after installation because we weren't sure about venting just yet. The one video on youtube for installing scissor trusses shows a couple guys installing them using frieze blocks, so we copied that system, mostly, but added more temporary bracing.

Sheathing alone is not enough to brace a roof truss system. It requires a bit more than that, but there seems to be a lot of variety and not a lot of consistent advice.


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> Take the freeze blocks out, there is no need for them.


Man, those blocks are nailed in with two nails on each end, that's going to be messy getting them out. I guess I could use a saws-all. 

Are you saying I don't need them because the soffit and venting will take care of all that? We just weren't sure about the venting yet. So much to read and learn and we're trying to beat the winter freeze to get it sheathed, sided and roofed so it's sealed. 

I've heard vaulted ceiling systems can get particularly hot up there. But I don't know much about venting, how much or how little. I know I'd like to not put gable vents in, but I'm not sure if soffit venting would be good enough. 

Thanks for your advice on the lower blocks for the sheet rock, that sounds like a great idea.


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## HenryMac (Sep 12, 2018)

timkoupe said:


> There is no designer or engineer involved in this project. And there are no permits or inspections where we are building.


So how do you know the design is up to the task when it comes to environmental conditions, such as wind loading?


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## Nealtw (Jun 22, 2017)

timkoupe said:


> Man, those blocks are nailed in with two nails on each end, that's going to be messy getting them out. I guess I could use a saws-all.
> 
> Are you saying I don't need them because the soffit and venting will take care of all that? We just weren't sure about the venting yet. So much to read and learn and we're trying to beat the winter freeze to get it sheathed, sided and roofed so it's sealed.
> 
> ...


 An 8 pound hammer would make quick work of the blocks but you need about 1 1/2 inches for an air gap, so you could go along with a saw and cut down 1/12" deep a couple inches on each side of the trusses and knock the top off the blocks.


Don't even think about venting, you want vented soffits with a fee flow of air to the peak where you put a ridge vent. No gable vents or anything else.


The green things in the picture are air chutes. 


https://www.homedepot.com/p/ADO-Pro...h-Built-In-Baffle-10-Ctn-UDVB234610/202389935


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## Nealtw (Jun 22, 2017)

High heel cuts are the normal here, I didn't realize you would have had to order them special


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## DIYOkie (Jun 27, 2013)

HenryMac said:


> timkoupe said:
> 
> 
> > There is no designer or engineer involved in this project. And there are no permits or inspections where we are building.
> ...


Well, because we visited job sites of houses under construction here, and these are expensive ones, multi-level and crazy roof systems. They were mostly 9' walls, all 2x4 walls and roof systems, 7/16 OSB sheathing, with anchor bolts spaced at 6'. 

Our house is a single level box, 900 sq feet, 2x6 walls, anchor bolts spaced at 4' and I'm adding a few more. Our trusses were made here in Oklahoma and we are using the 7/16 APA 24/16 exposure 1 rated OSB that all the lumber stores have stacked up front for framing contractors. 

And I did consult with 2 engineers over the phone about it, although that's not the same as a full blown design. They both said a shear wall was absolutely unnecessary. We are using hurricane ties as well. I feel pretty good about this modest home plan giving us a solid structure for our area. 

I can't imagine what my little house needs that these multi-level fancy houses don't. 

I understand your question, and it bothered me enough to research it enough that I feel good about it. Next house will be a bit more complicated, and I am going to want a full blown design and blueprints.


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## Nealtw (Jun 22, 2017)

I don't remember, are you doing look outs? and gutters?


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> I don't remember, are you doing look outs? and gutters?


I had planned on doing lookouts, although it would be nice not to have to mess with it. Gutters, absolutely.


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> An 8 pound hammer would make quick work of the blocks but you need about 1 1/2 inches for an air gap, so you could go along with a saw and cut down 1/12" deep a couple inches on each side of the trusses and knock the top off the blocks.
> 
> 
> Don't even think about venting, you want vented soffits with a fee flow of air to the peak where you put a ridge vent. No gable vents or anything else.
> ...


Well that's pretty interesting. So I could just remove the frieze blocks completely, it looks like, and install those rafter vents, and then the soffit should keep the bugs out of my roof system, right? Seems pretty simple. 

Are air chutes better than those rafter vents? They seem like the same concept, just a little different implementation.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> I had planned on doing lookouts, although it would be nice not to have to mess with it. Gutters, absolutely.


We build the look outs just like the video except we build them in place.


My question about gutter was just if you ever want gutters the ends of the trusses want to be a plumb cut.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> Well that's pretty interesting. So I could just remove the frieze blocks completely, it looks like, and install those rafter vents, and then the soffit should keep the bugs out of my roof system, right? Seems pretty simple.
> 
> Are air chutes better than those rafter vents? They seem like the same concept, just a little different implementation.


 No the chutes just give you an open hole, We do a vented soffit under the eaves.


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## Nealtw (Jun 22, 2017)

This is what is common here but we do gutters on everything and no fascia behind them and a lot of cheating is done from these instruction but you get some ideas here.


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> No the chutes just give you an open hole, We do a vented soffit under the eaves.


No, I mean the air chutes create a hole for air, and so do those rafter vents you linked - they both provide a hole for air. So which one is better?


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## DIYOkie (Jun 27, 2013)

On the bracing though...the 2015 International Residential Code refers to the 2015 BCSI for truss bracing. 

It's requiring bracing everywhere you can possibly imagine. Lateral and diagonal bracing for the web plane, the bottom chord plane...and now it's on about T and L bracing for individual chord members to prevent buckling and etc..

I'm worn the hell out on this. I've never seen this kind of bracing in any house I've ever lived in.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> No, I mean the air chutes create a hole for air, and so do those rafter vents you linked - they both provide a hole for air. So which one is better?


 Up here every house gets vented vinyl soffit. But they do it easier than that video. We do a plumb cut on the truss tails with a 2x4 liner across the ends 
flush to the bottom of the tail, then a gutter or fascia or both.
The J channel for the soffit is screwed up to the 2x4 liner and if the fascia or gutter is wavy the J channel can be made to fit that and hide any flaws. 
Then they use a F channel on the wall level with the liner and it is ready for soffit, no one here adds screws to the soffit itself. You just have to remember to turn the saw blade around to cut this stuff.


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## viper (Jul 30, 2009)

timkoupe said:


> And I did consult with 2 engineers over the phone about it, although that's not the same as a full blown design. They both said a shear wall was absolutely unnecessary. We are using hurricane ties as well. I feel pretty good about this modest home plan giving us a solid structure for our area.


Maybe I missed it but what shear wall are you talking about because shear is the basis for that entire structure working! 

I just realized you were in OK, and you have an 8/12 roof? Is this just an effort to get a nice vaulted ceiling? It can work but your primary load is wind and lots of it. Wind on a 8/12 on the sidewalls presents a largely unbalanced load that the roof needs to be designed for.


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## SeniorSitizen (Sep 10, 2012)

viper said:


> Is this just an effort to get a nice vaulted ceiling?


That's something I always wanted to know but was afraid to ask.:smile:Maybe we'll get an answer.


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## Yodaman (Mar 9, 2015)

Regarding the freeze blocks, if you were to insulate for a unvented roof deck, I believe you could leave them in. Generally this is done with high density spray foam. Not suggesting this is doable for your project, only that it is a viable technique that eliminates the attic and roof deck venting altogether


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## 123pugsy (Oct 6, 2012)

timkoupe said:


> On the bracing though...the 2015 International Residential Code refers to the 2015 BCSI for truss bracing.
> 
> It's requiring bracing everywhere you can possibly imagine. Lateral and diagonal bracing for the web plane, the bottom chord plane...and now it's on about T and L bracing for individual chord members to prevent buckling and etc..
> 
> I'm worn the hell out on this. I've never seen this kind of bracing in any house I've ever lived in.



If these are engineered trusses, what do the drawings say?
Have you contacted the truss supplier with your questions?


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## Nealtw (Jun 22, 2017)

timkoupe said:


> On the bracing though...the 2015 International Residential Code refers to the 2015 BCSI for truss bracing.
> 
> It's requiring bracing everywhere you can possibly imagine. Lateral and diagonal bracing for the web plane, the bottom chord plane...and now it's on about T and L bracing for individual chord members to prevent buckling and etc..
> 
> I'm worn the hell out on this. I've never seen this kind of bracing in any house I've ever lived in.


 Did you just buy these from a yard or were they built specific for your house.
If the latter the stamped information that came with them will have the bracing you need. The code is way over the top


If they are showing an L on a bunch in a row, we are allowed to but and L on each end of that and join them all together with a lateral 2x4 in the middle.


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> Up here every house gets vented vinyl soffit. But they do it easier than that video. We do a plumb cut on the truss tails with a 2x4 liner across the ends
> flush to the bottom of the tail, then a gutter or fascia or both.
> The J channel for the soffit is screwed up to the 2x4 liner and if the fascia or gutter is wavy the J channel can be made to fit that and hide any flaws.
> Then they use a F channel on the wall level with the liner and it is ready for soffit, no one here adds screws to the soffit itself. You just have to remember to turn the saw blade around to cut this stuff.


No, I mean the air chutes create a hole for air, and so do those rafter vents you linked - they both provide a hole for air. So which one is better?


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## DIYOkie (Jun 27, 2013)

viper said:


> Maybe I missed it but what shear wall are you talking about because shear is the basis for that entire structure working!
> 
> I just realized you were in OK, and you have an 8/12 roof? Is this just an effort to get a nice vaulted ceiling? It can work but your primary load is wind and lots of it. Wind on a 8/12 on the sidewalls presents a largely unbalanced load that the roof needs to be designed for.


A shear wall is a specialized structure for particular lateral/shear loading concerns. Apparently, some home designs require more shear strength than what you get from your structural sheathing and stud wall system. They seem to build it in some kind of centralized location in the home, and walls throughout the home are tied to it. 

It seems to be a concern on multi-level homes and other conditions. I had to ask about it, being in tornado alley. I am not an expert about any of that. 

And your observation about wind loading is precisely what has been driving my bracing concerns.


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## DIYOkie (Jun 27, 2013)

SeniorSitizen said:


> That's something I always wanted to know but was afraid to ask.:smile:Maybe we'll get an answer.


Yes, just to get a nice vaulted ceiling because the home is small. We are just building a small home cabin-in-the-woods kind of thing, and since the living room/kitchen is only 22' x 16', we wanted vaulted ceilings to add some space. We have noticed in the past that high ceilings help a room feel bigger even when the floor space is still small.


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## DIYOkie (Jun 27, 2013)

123pugsy said:


> If these are engineered trusses, what do the drawings say?
> Have you contacted the truss supplier with your questions?


We bought these through Lowe's. They are made by a truss manufacturer here in Pryor Oklahoma. We never gave them drawings to design them from, rather we said we need 19 scissor trusses and 2 gable trusses for a 22' span. 

We have reached out to them, so far our initial response is a summary sheet straight from the 2015 BCSI guide put together by truss manufacturers and referenced by the 2015 IRC. 

And that's why I'm here...


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## Nealtw (Jun 22, 2017)

timkoupe said:


> No, I mean the air chutes create a hole for air, and so do those rafter vents you linked - they both provide a hole for air. So which one is better?


The soffit is the area under or between truss tail, between the the fascia and the house. 
Air chutes provide a gap between the insulation and the roof sheeting over the wall. 


So before you insulate you staple air chutes against the bottom of the sheeting over the wall so when you insulate air can get into the attic from the soffit area.
Vented soffits is the finish on the outside that lets air into the soffit area, part of the siding job.
So you need both.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> A shear wall is a specialized structure for particular lateral/shear loading concerns. Apparently, some home designs require more shear strength than what you get from your structural sheathing and stud wall system. They seem to build it in some kind of centralized location in the home, and walls throughout the home are tied to it.
> 
> It seems to be a concern on multi-level homes and other conditions. I had to ask about it, being in tornado alley. I am not an expert about any of that.
> 
> And your observation about wind loading is precisely what has been driving my bracing concerns.


We do shear wall for seismic activity here. They have heavy straps from the foundation up onto the wall and the sheeting on the wall gets nailed every 2" around the perimeter all the joins have solid blocking behind them.


there might be one or two walls on the outside and one on the insides. 
The inside ones just get OSB behind the drywall and the walls are tied to the floor or the wall above and below,.
The problem with them is door jams have to be ordered or made for 1/2" thicker walls.


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## viper (Jul 30, 2009)

I just wanted to make sure about the "shear walls" because a shear wall is just something that is being primarily loaded in shear and can be anywhere in a structure. Hell, the entire shell is a shear wall. 

No sir, for the dimensions of your building, if you needed a central shear wall, you likely would have some design flaw in your structure. 

The only thing I don't like is the 8/12 pitch for wind because in certain events, it can cause very high tension in the bottom chords. Never the less, it is going up. 

Because you are in T.A., and I am too, I will share a few pointers but I will not design your building because you will find that engineers really will want to know the details right down to the nail size and schedule on the footers. 

There is a certain point where you have to accept that wind is just going to take the structure. You've seen it happen. Let me explain a few things. You push on that nice shell, it loads up evenly, everything works. However, consider the building like a ship, once a panel is compromised, the end is near. When you watch slow video of a nader taking a home, usually the start is a roof sheet being "sucked" off. Typically the leeward side of a high pitch roof has serious neg pressure, then a window is blown out and the structure is pressurized and that causes it to lift even more. 

This becomes a game of "how far do you want to take this?". Technically the roof system should be screwed NOT nailed, but it could be reasoned that I might like to see 3x the nails in the roof system which helps in shear. If you are nailing, get happy with the nails up there!! Especially the eve and peak edges that form your diaphragms. 

The reason I mention how the structure fails is we like to add redundancy to a structure with straps, lumber, etc, that will assist in shear if a panel fails. Let me pepper some breadcrumbs. Steel is a friggin MASTER of tension. It is cheaper than wood for this application. If you want a cheap and easy way to reinforce a structure, you can consider X braces on all walls with thin gauge steel straps. however, The steel will load up in tension and the complication becomes how to transfer all that load into the strap. A couple nails won't even get close. Let me explain. 

You consider a tension strap that would see tension of 10,000lbs. Say you use typical A36 steel which has a yield of 36ksi. Now, you NEVER design to yield so lets just work with half of that, so 18ksi. So to select a strap, you consider 10ksi/18ksi=.56sqin of material. You are around .125x4". Pretty big! However, steels can easily exceed 100ksi yield with the right allow and temper, so using a higher strength material is preferred. 

However, you still have to manage all that force at the ends! Even if the steel would take it, the wood won't without including a lot of nails. 

What I am trying to get at is the ENDS of your braces are VERY important and I see this all the time where someone will throw up some beefy 2x8s thinking they are doing something, but pop a couple nails in each end.... 

When you consider your roof, sidewall wind loads will but downforce on the windward side which will put the TCs in compression so buckling becomes a concern. Running a couple 2x4s on each side, along with the sheathing will help prevent this until she can't take any more. actually the 2x4s on edge on the bottom of the TCs is preferred but would be impractical to do. 

The BCs are primarily in tension so buckling is less a concern BUT they are completely unsupported and that is never a good idea. Sometimes the finish overrides function or ultimate support because ideally you may want a lateral 2x4 near the peak on each side, then X braces in the 4 quadrants of the roof....(ideally). And I say that because you probably won't see that in construction! Why? Because they are designed to a certain limit, then insurance kicks in. 

We we looked at how to optimize a structure for wind, it really does come down to "how much is enough?" I can tell you in our county, 90mph GUST is the design spec.....LOL On open land, that load is nearly guaranteed so designing to that min spec seems ridiculous. 

If you want to ensure yours does not come down, do NOT skimp on your fastener schedules for all exterior sheathing. Loads are more dispersed in more lumber and the structure will be stiffer.


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> The soffit is the area under or between truss tail, between the the fascia and the house.
> Air chutes provide a gap between the insulation and the roof sheeting over the wall.
> 
> 
> ...


We're getting closer....

I'm just going to get whichever one Lowe's has, I guess. I understand about the soffits and the venting concept, all of that. I'm talking about the fact you linked to a product that claims to be called Rafter Vents, but then you also added a picture of Air Chutes, a different product. Both products are installed over the wall opening to provide air flow into the attic when you insulate. It's an either/or, not both. 

Whether I use Air Chutes or Rafter Vents, either of them require vented soffits to let air in. 

I think you're misunderstanding my question, but that's ok.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> We're getting closer....
> 
> I'm just going to get whichever one Lowe's has, I guess. I understand about the soffits and the venting concept, all of that. I'm talking about the fact you linked to a product that claims to be called Rafter Vents, but then you also added a picture of Air Chutes, a different product. Both products are installed over the wall opening to provide air flow into the attic when you insulate. It's an either/or, not both.
> 
> ...


 I have misunderstood many things in my life. :biggrin2:


Yes these things come in all shapes sizes, material and names. they all supply air over the insulation above the exterior wall.
Sorry for the confusion.:vs_cool:


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## DIYOkie (Jun 27, 2013)

viper said:


> I just wanted to make sure about the "shear walls" because a shear wall is just something that is being primarily loaded in shear and can be anywhere in a structure. Hell, the entire shell is a shear wall.
> 
> No sir, for the dimensions of your building, if you needed a central shear wall, you likely would have some design flaw in your structure.
> 
> ...


I'm not sure how to respond to all this. It's fascinating, but you're scaring the crap out of me. 

Ok...so on the roof sheathing. We plan to use .131" x 2.5" nails. I was reading we needed to nail every 6" on center on the edges, and 12" on center in the field. (That's about 56 nails per panel, wow). Then I also read the footnote that mentioned for wind loads over 130 MPH, you should reduce those to 4" at the edges, and 6" in the field when you're within 48" of a ridge, gable end, or eave. (That would be about 88 nails per panel.)

On the bracing...web member bracing. We ended up putting one 2x4x12' at the peek of the gable truss running downward diagonally, nailing into the center vertical chord of the first 5 trusses. Then ran another one on the other side, but used a 2x4x16' which managed to wedge itself against the 6th or 7th truss, and again, nailed into the vertical chord of other 5 or 6 trusses. 

We did that on the other gable end also. So that's two 2x4's on each end, running diagonally from the peak of the gable truss. 

Then we went to the middle and formed an X shape by putting a 2x4x12' on both sides of the vertical chords, running diagonally. 

Then we went to the 2 outside vertical web member chords and ran diagonal braces against those with 2x4x12', on both ends, running the opposite diagonal from the first gable peak trusses we did in the middle. 

And, of course, we did nail 2 catwalks along the bottom chords from one end to the other with 2x4x12's. 

It's hard to say if this will be enough bracing. These are scissor trusses, so you can't get the same angles as you can with a regular truss. 

The BCSI literature claims the gypsum board serves as the bottom chord bracing and lateral restraint, although we do have the catwalks to aid with lateral restraint. It also claims the roof sheathing serves as the top chord bracing and lateral restraint. And, it says you're supposed to do the diagonal web member bracing across the 3 vertical (somewhat vertical) web members with minimum and maximum spacings and we made sure we stayed within that tolerance. 

It still shocked me how after all of that bracing I could still make the trusses kind of flex - but I had to rhythmically push on them pretty good. I'm just not sure where else I'd put bracing, unless I started running more diagonals on the bottom chord plane. 

Everyone keeps saying the sheathing will strengthen all that up. Well sure...but like you said, when it starts peeling off in a wind storm, I need that bracing.


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## viper (Jul 30, 2009)

Here you can see the shear failure in the walls due to gable end wind loading. This could have been prevented with additional shear protection in the walls.


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## viper (Jul 30, 2009)

The one thing that test fails to apply is flying debris which will be guaranteed in real life, which typically blasts out windows, and causes pressure changes within the structure, and likely would have changed the failure mode in this instance. Only takes a small rock at 100mph to do the job. 

What I have seen is people build a structure without the forethought of failures in their area and skimps on nailing schedules, etc. It cannot be understated that those schedules along with nail type are VERY important. Screws would be preferred but you can see that can be impractical. What is interesting is structural tests done immediately after assembly in which the nails still have good withdraw strength. Over time, wood will move and can cause nails to become loose. People taking older homes apart will notice nails come out very easy. This is why glue nails, screw nails, ring shanks, etc, are preferred. I also prefer plywood over OSB. 

As you are doing, the truss to wall connection has to be extreme. Toe nails are NOT sufficient. 

A friend of mine has a post frame building that I already warned will not hold up to a serious event. It recently was hit with 90mph diffused wind. The 2x4 roof purlins were laid flat across the TCs and simply nailed. In that event, those purlins lifted about 1" and the structure was very near complete failure. Had the door been compromised, it would have pressurized the building and certainly pulled the roof off.

If there is one thing I can offer, it would be to add additional screws at the eves on the roof panels. Those are common to get peeled up and starts the failure on the windward side. That is cheap and easy!!!!


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## viper (Jul 30, 2009)

Regarding that video. I slowed it down and confirmed that the entry door was blown open, pressurized the lower level, and the shear wall sheathing was blown/sucked off, causing the failure. I suspect if the upper windows had blown in, the roof would have been removed. 

This is why withdraw cannot be understated. Slow it down and you can see the entire wall come off. Once that occurs, there is nothing left on that side to support the loads.


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## Nealtw (Jun 22, 2017)

@viper We don't get wind like that, so lot's of great info here. 
We always see or hear about people huddled in the bathroom, I have always wondered why they never built the bathroom and it's ceiling as stress wall with an independent ceiling that would not leave with the roof structure. Thoughts?


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## viper (Jul 30, 2009)

Neal, the safest place to be is in a hole! AKA, basement! They are rather standard in the midwest. 

main level storm shelters are not typically done but I have certainly designed one into my own building and know others than have. The issue is not just wind survival but that big oak tree flying your way. Surviving an F4-F5 is tricky and a gamble above ground. A concrete structure can certainly take it BUT, every detail must be considered. 

As per my own, a properly designed interior storm shelter should be an independent structure from the rest, correctly anchored to a concrete base slab, reinforced walls AND ceiling. And a REAL steel door. And even at that, if I knew an F5 was coming, I would still run out and climb into a culvert! 

In TA, you will commonly see below ground structures near a home. It is cheap and works well. Has been proven over the past 100yrs.

Oh, I should mention, many people that live here still have no clue how naders do their thing. many people die even in a basement from being sucked out or debris. Even in a basement, you really need a fortified ceiling. they are becoming more and more common. 

The very best is a suspended concrete garage floor! You make that part of the basement space and built that into your nice theater space. The concrete floor above provides a nice ceiling. Also, the porch area of homes is now being used because the porch is concrete.


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## DIYOkie (Jun 27, 2013)

viper said:


> https://www.youtube.com/watch?v=ga7N-bS4nLU
> 
> Here you can see the shear failure in the walls due to gable end wind loading. This could have been prevented with additional shear protection in the walls.


I love how they don't tell you what the reinforcements were or anything about the home on the right that didn't fail. 

Would you just add more structural panels, like on the inside before you put drywall up? And what would you do to the attic / roof structure to keep it from failing?


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## Nealtw (Jun 22, 2017)




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## viper (Jul 30, 2009)

Excellent video! I love the hard hat in the office....:vs_laugh: I firmly agree with steel reinforcements. If builders actually follow the design, it will work. however, I have seen nails shot off center of the prefab holes, and that is NOT cool! A nail piercing the metal will create tears which will quickly propagate into cracks. 

I did not see any provisions for negative pressure on the panels but I am sure it is there. Technically if the wood will pull over the fastener, the only other thing you can do is add more fasteners. Actually the gold standard right from aerospace is to 100% glue the panels! This would be a real bear to replace but you can sleep good knowing you probably have doubled the structural capacity of the panels! 

If you want a roof that won't come off, F26 Those suckers on!

What we have realized in our research is we know exactly what we "want" to use to reinforce the structure, but it has to be something that is quick and easy. We LOVE all thread rod! We can pretension it, and know exactly what it can take, but applying that to walls is not much fun. Do you want to drill about 100, 45* holes in your stud walls? 

Really, to be honest, those steel straps and glue will make you one helluva building. At some point though, mother nature always wins.


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## 123pugsy (Oct 6, 2012)

My framer thought I was nuts when I gave him 5/8 T&G plywood for my roof. I just like the idea of something that will keep my "box" good and square even though I'm nowhere near a high wind zone.


He even commented on the 16" centers trusses being overkill.


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> I have misunderstood many things in my life. :biggrin2:
> 
> 
> Yes these things come in all shapes sizes, material and names. they all supply air over the insulation above the exterior wall.
> Sorry for the confusion.:vs_cool:


No worries, same here my friend. 

So...now I need to frame a covered front porch. It is 16' wide, and 5 foot off the front of the house. The pitch of its roof will be opposite. For this, I was going to go with a ridge board, cut rafters and rafter ties/ceiling joists, something fairly simple for the roofing system. I have seen a couple videos on how to get the rafters cut as you close in on the adjoining roof. 

What about the framing and posts for the roof system to sit on? I was hoping to use treated 4x4 posts on the corners with a center span of about 10 to 12' wide. I guess I need to look up the correct dimensional lumber size for that span. 

Should I start a new thread?


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## Nealtw (Jun 22, 2017)

timkoupe said:


> No worries, same here my friend.
> 
> So...now I need to frame a covered front porch. It is 16' wide, and 5 foot off the front of the house. The pitch of its roof will be opposite. For this, I was going to go with a ridge board, cut rafters and rafter ties/ceiling joists, something fairly simple for the roofing system. I have seen a couple videos on how to get the rafters cut as you close in on the adjoining roof.
> 
> ...


 I would have just ordered jack trusses for that. 
Posts are 6x6, 4x4 is history now, if you intend to wrap them for pretty, 4 treated 2x6 are less likely to warp and twist. 
Did you put footing and piers in. That's a must for a roof( frost depth.)
See if you can find a picture on the net of something like your house with a roof look that you have in mind


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> I would have just ordered jack trusses for that.
> Posts are 6x6, 4x4 is history now, if you intend to wrap them for pretty, 4 treated 2x6 are less likely to warp and twist.
> Did you put footing and piers in. That's a must for a roof( frost depth.)
> See if you can find a picture on the net of something like your house with a roof look that you have in mind


I'm confused. I didn't even put piers in for my home, let alone for a porch roof. And no, we didn't have footings poured for the porch, I didn't think they did that. I thought patios and porches were just 4" slabs without any footing.

I could possibly work out a solution putting posts down into the dirt, cemented in, like fence posts, but I can't get footing under the porch now.


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## DIYOkie (Jun 27, 2013)

This is a pretty good analogy right here. The manufactured home is a rectangle, like ours, with a roof direction like ours, and the porch centers on the front with the roof going the other direction. 4 pillars, or posts, and it's all on the same floor level with the house. 

Just remove the stairs and the brick foundation looking stuff and there's our house and porch for the most part. I was even planning on a lower pitch than the rest of our house too. Like 5/12 or 4/12, maybe.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> I'm confused. I didn't even put piers in for my home, let alone for a porch roof. And no, we didn't have footings poured for the porch, I didn't think they did that. I thought patios and porches were just 4" slabs without any footing.
> 
> I could possibly work out a solution putting posts down into the dirt, cemented in, like fence posts, but I can't get footing under the porch now.


 The slab is fine because it can move with out hurting anything but if the roof moves, you have a problem.
Just like you said dig a hole but just put concrete in it and a saddle on top to hold the post. We would just uses an eight inch hole with smooth sides with a sono tube just to bring it out of the ground neat, But if the hole has rough sides you put 8" of concrete in the bottom and then add the tube from there and brace the top so it stands straight. Some places call for much bigger tubes so you need to find what is being used in the area. 
The hole has to be smooth sides so there are no ledges for frost to get under and lift it.


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## Nealtw (Jun 22, 2017)

With trusses and a valley set, you would need 2 posts, 2 beams depending on load might be 2 or 3 2x10s back to the house usually cut into the wall and set on jack studs, the top would be level with the 
top plate. We often put a beam across the front too, just for looks but often it does more hanging from the gable than supporting anything.


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> The slab is fine because it can move with out hurting anything but if the roof moves, you have a problem.
> Just like you said dig a hole but just put concrete in it and a saddle on top to hold the post. We would just uses an eight inch hole with smooth sides with a sono tube just to bring it out of the ground neat, But if the hole has rough sides you put 8" of concrete in the bottom and then add the tube from there and brace the top so it stands straight. Some places call for much bigger tubes so you need to find what is being used in the area.
> The hole has to be smooth sides so there are no ledges for frost to get under and lift it.


What if we build an independent porch structure that simply does not actually touch or tie-in to the home and roof system? Could I simply build it on the porch slab like its own structure so it could actually move without hurting anything?


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## viper (Jul 30, 2009)

timkoupe said:


> What if we build an independent porch structure that simply does not actually touch or tie-in to the home and roof system? Could I simply build it on the porch slab like its own structure so it could actually move without hurting anything?


This would not be a good idea. You are talking about building one of the weakest structures there is! In tornader alley! Tie that thing into your main structure. 

Your porch support column footings will need serious design work. You are putting an airplane wing out there. Make sure it doesn't take off.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> What if we build an independent porch structure that simply does not actually touch or tie-in to the home and roof system? Could I simply build it on the porch slab like its own structure so it could actually move without hurting anything?


No...........


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## DIYOkie (Jun 27, 2013)

Sounds to me like I need to dig the column footings right off the front of the porch. This really sucks too, we have rock 12" down and I'd have to go 24" at least to get under the frost line. 

Not sure how I'm going to deal with the cosmetics of columns sitting just off the front of the porch slab. I'm also not excited about decorating them up with more material, I'd rather just have solid posts.



Nealtw said:


> With trusses and a valley set, you would need 2 posts, 2 beams depending on load might be 2 or 3 2x10s back to the house usually cut into the wall and set on jack studs, the top would be level with the
> top plate. We often put a beam across the front too, just for looks but often it does more hanging from the gable than supporting anything.


I'm not visualizing where those 2 beams would go. And how do you add 2x10's back to the house and set on jack studs and somehow be level with the top plate? You're not suggesting I actually cut into and notch out the top plate are you? 

I'd rather tuck them just under the top plate, keep it whole and continuous, and add material at the top around the porch roof base to make it level with the top plate.

It's hard to visualize with words a computer screen. I've always had a hard time turning words into pictures. 

I'm considering a very low pitch on this, like 1/12 or 2/12, something a little more flat.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> Sounds to me like I need to dig the column footings right off the front of the porch. This really sucks too, we have rock 12" down and I'd have to go 24" at least to get under the frost line.
> 
> Not sure how I'm going to deal with the cosmetics of columns sitting just off the front of the porch slab. I'm also not excited about decorating them up with more material, I'd rather just have solid posts.


 As in solid rock or just nasty stones to dig out?


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> As in solid rock or just nasty stones to dig out?


In some places, nasty stones, in others solid rock. When we dug out the electrical and water trenches we ran into mainly nasty stones to dig out, but when the septic guy installed the aerobic system he had to break into solid rock and added almost a thousand dollars to the job.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> Sounds to me like I need to dig the column footings right off the front of the porch. This really sucks too, we have rock 12" down and I'd have to go 24" at least to get under the frost line.
> 
> Not sure how I'm going to deal with the cosmetics of columns sitting just off the front of the porch slab. I'm also not excited about decorating them up with more material, I'd rather just have solid posts.
> 
> ...


 I would draw scaled drawings of different pitches before I went to low.
The same pitch puts the fascia or gutter in the same line. Changing the pitch to a lower pitch would lower the beam to align the gutter line 
This video shows a few ways to do the beam. but I would say ignore the ones where he notches the beam, that is not acceptable in almost all cases. There are 2 others that he didn't tough on.
1. 2 2x8s on the flat inside the sheeting and use hangers on the outside 
2. if you have used 2x6 studs a flush beam can sit on 2x4s so you only remove 3 1/2" of the top plates..


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## Nealtw (Jun 22, 2017)

Thought I would drop off a couple pictures showing a basic wrap on the posts and beams. And sometimes they go no nuts. The last picture is fir posts and beams with one timber truss in front of scissor trusses


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> I would draw scaled drawings of different pitches before I went to low.
> The same pitch puts the fascia or gutter in the same line. Changing the pitch to a lower pitch would lower the beam to align the gutter line
> This video shows a few ways to do the beam. but I would say ignore the ones where he notches the beam, that is not acceptable in almost all cases. There are 2 others that he didn't tough on.
> 1. 2 2x8s on the flat inside the sheeting and use hangers on the outside
> ...


Yeah, I really prefer the last one he covered. Nothing gets notched, all stays strong. But the head space might be a small issue...but I only gain 3 inches by trying to notch the top plate and strap. 

Here's the thing...since the porch is only 5 feet deep, I only need 2x that is wide enough to support a 5' span. Now the front beam, that spans 12', that one might need to be taller 2x material I guess. Although..what about LVL or something that doesn't require gigantic wide pieces of dimensional lumber?

I was looking up the width of material by looking at "header" tables that support roof load only, not walls. For a 12' span, it says (2) 2x12's for number 1 grade, and (3) 2 x 12's for number 2 grade. That sure seems like a lot.


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## DIYOkie (Jun 27, 2013)

Actually...thinking about this, the load is sitting on the two short outside beams, the 5' pieces that run from the house wall jack studs to the front. They are taking all the weight of the roof system, and sitting on the two columns. The front beam doesn't support any weight, does it? 

I think that's what you were telling me in an earlier post and that didn't register until just now. I'm slow...but I'll get there eventually! 

So..if that's true, the span table says I only need a single 2x8 number one grade, or a single 2x10 number 2 grade for a 6' clear opening supporting a 16' roof span. And I can just use the same to run along the front since it doesn't need to be sized for any loading.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> Actually...thinking about this, the load is sitting on the two short outside beams, the 5' pieces that run from the house wall jack studs to the front. They are taking all the weight of the roof system, and sitting on the two columns. The front beam doesn't support any weight, does it?
> 
> I think that's what you were telling me in an earlier post and that didn't register until just now. I'm slow...but I'll get there eventually!
> 
> So..if that's true, the span table says I only need a single 2x8 number one grade, or a single 2x10 number 2 grade for a 6' clear opening supporting a 16' roof span. And I can just use the same to run along the front since it doesn't need to be sized for any loading.


 We never look at span tables. just read plans and never seen a single anything holding up a roof, every here gets 2 2x10 min. , consider wind loading too.


Just some thoughts.


A lower pitch on the front may put the beam on top of the wall instead of cut into it. 
A beam under the front is optional not needed except for looks and can be a wall just hung off the gable to match the beams on the sides


If you don't want to dress the posts you could make the posts and beams look a little timber style with #1 fir post and 4x10 rough fir beam.


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## Nealtw (Jun 22, 2017)

timkoupe said:


> Yeah, I really prefer the last one he covered. Nothing gets notched, all stays strong. But the head space might be a small issue...but I only gain 3 inches by trying to notch the top plate and strap.
> 
> Here's the thing...since the porch is only 5 feet deep, I only need 2x that is wide enough to support a 5' span. Now the front beam, that spans 12', that one might need to be taller 2x material I guess. Although..what about LVL or something that doesn't require gigantic wide pieces of dimensional lumber?
> 
> I was looking up the width of material by looking at "header" tables that support roof load only, not walls. For a 12' span, it says (2) 2x12's for number 1 grade, and (3) 2 x 12's for number 2 grade. That sure seems like a lot.


 8 ft wall inside? , where is the deck outside, lower than the floor or close to level with floor inside?


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## viper (Jul 30, 2009)

timkoupe said:


> So..if that's true, the span table says I only need a single 2x8 number one grade, or a single 2x10 number 2 grade for a 6' clear opening supporting a 16' roof span. And I can just use the same to run along the front since it doesn't need to be sized for any loading.



You better make sure what the loads are in the span table as well as allowable deflections. L/? In most lumber applications in bending, the deflection drives the load, not really its strength limits. 

Also, lumber has a serious problem with creep so really any appreciable deflection with the dead weight applied may cause problems in the long run.


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## DIYOkie (Jun 27, 2013)

viper said:


> You better make sure what the loads are in the span table as well as allowable deflections. L/? In most lumber applications in bending, the deflection drives the load, not really its strength limits.
> 
> Also, lumber has a serious problem with creep so really any appreciable deflection with the dead weight applied may cause problems in the long run.


Yes, that was just a quick lookup to get a feel for what I'll actually need. I am a bit worn out on this today, so first thing in the morning I'm going to run through this tutorial for looking up spans. 

https://www.awc.org/codes-standards/spantables/tutorial

I did manage to find the code information for my area. I live just outside of Tulsa County, and we don't have permits out here, so I'm using Tulsa's codes as a reference. They mainly use the 2015 IRC with amendments here and there. 

The code specifies ground snow load @ 10 PSF, wind load at 115 mph, seismic category A. 

But I'm not sure where to find my live load. It's not a "room other than sleeping room" (40 psf). It's not a sleeping room (30 psf)...I'm not sure how a porch falls into any of these IRC categories for live load.


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## Nealtw (Jun 22, 2017)

viper said:


> You better make sure what the loads are in the span table as well as allowable deflections. L/? In most lumber applications in bending, the deflection drives the load, not really its strength limits.
> 
> Also, lumber has a serious problem with creep so really any appreciable deflection with the dead weight applied may cause problems in the long run.


 Creep? I can guess but I would sooner know what you are referencing.


I would think the front porch would be a big sail and will need to be seriously tied down? Exposed beams might not be appropriate?


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## viper (Jul 30, 2009)

timkoupe said:


> But I'm not sure where to find my live load. It's not a "room other than sleeping room" (40 psf). It's not a sleeping room (30 psf)...I'm not sure how a porch falls into any of these IRC categories for live load.


I suspect you are looking at floor loads, not roof because a roof should have a uniform live for the entire thing. Hint, the local jurisdiction may decide what this is because it basically amounts to construction traffic on the roof. If not, I believe the IRC has language in it. 

If I had to guess in your area, probably 20-25psf.


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## viper (Jul 30, 2009)

Nealtw said:


> Creep? I can guess but I would sooner know what you are referencing.
> 
> 
> I would think the front porch would be a big sail and will need to be seriously tied down? Exposed beams might not be appropriate?


Creep basically amounts to sag over time. It is very frustrating with lumber because it deflects pretty easy and doesn't take much to cause a problem. If you put sticks together, I am sure you have seen the effects on a roof that was not built right. Dips and sags. 

Also, regarding live loads, even though loads are within range, it is VERY typical to exceed code requirements to reduce the deflection of a floor so it feels "solid" when you walk on it. Been in a house with a spongy floor? It might not ever "fail", but it sure doesn't feel like quality either.



I see no issue with exposed beam. It can all be designed up. What I think is funny is being in "the alley" myself and being in aerospace, the first thing I want to do is design with aerodynamics in mind. It just doesn't happen with buildings! Anyone wanna guess why those big grain silos continue to stand after a nader? LOL 

Basically you just keep throwing lumber until the issue is solved. The biggest issue surrounding the porch is uplift but that is putting the columns in tension and easily manages with the right embedments and uplift protection.


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## Nealtw (Jun 22, 2017)

viper said:


> Creep basically amounts to sag over time. It is very frustrating with lumber because it deflects pretty easy and doesn't take much to cause a problem. If you put sticks together, I am sure you have seen the effects on a roof that was not built right. Dips and sags.
> 
> Also, regarding live loads, even though loads are within range, it is VERY typical to exceed code requirements to reduce the deflection of a floor so it feels "solid" when you walk on it. Been in a house with a spongy floor? It might not ever "fail", but it sure doesn't feel like quality either.


 Thank you, it drives me nuts when people look to make floors out of the smallest joist that fit the span. Where I leave a floor is never less than 2x10, and we don't like them when they get close to 16 ft.


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## viper (Jul 30, 2009)

Nealtw said:


> Thank you, it drives me nuts when people look to make floors out of the smallest joist that fit the span. Where I leave a floor is never less than 2x10, and we don't like them when they get close to 16 ft.


See this is something most builders do not understand. Floor joists vs floor trusses. Even if both will "carry the load", I will still select a truss every single time I can. Why? Because a truss will act the same as a very tall piece of solid lumber. If you look up loads in a beam, you will see there is compression on top, and tension in the bottom, and "neutral axis" which sees tremendous shear force. 

A truss acts like the almighty triangle, which is the pinnacle of design engineering. We LOVE them! Why? because when you push down on a triangle, we can move that down load to compression in two legs, and tension in the bottom. Stiffer! 

If I had to use joists, I would select engineered wood Ibeam. Why? Because in both plywood and OSB, the fibers are oriented at different angles within the plies to reduce the issues of having load normal to the direct of the grain. Wood behaves different depending on grain. Look at shear capacity parallel to grain and normal to grain. Total different. 

Now, I am not saying it is always practical because of costs! That's why you don't see it as much, but they are better.


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## viper (Jul 30, 2009)

Here is a pic of a quick down and dirty test on a wood Ibeam in 5 point. The display in back is in lbs of force. These were glued up with structural adhesive. Without the adhesive, these would not have worked. That is pine 2x2 for the flanges, and 1/2" ply for the web. I believe it was 4" tall.


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## DIYOkie (Jun 27, 2013)

Regarding the scissor truss bracing...here's some pics I took yesterday. I'm not sure where else I could brace except maybe the bottom chords on the outsides. Already have catwalks there and the BCSI says gypsum board serves as bottom chord bracing.


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## Nealtw (Jun 22, 2017)

I looks strange we sheet everything as we go. That would be all good where I am but that's a more local thing. 
Do you have a plan for the wall behind the gable that has to be built?


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## DIYOkie (Jun 27, 2013)

Nealtw said:


> I looks strange we sheet everything as we go. That would be all good where I am but that's a more local thing.
> Do you have a plan for the wall behind the gable that has to be built?


I think you're talking about the fact there is a 4" gap up at the top plate since the gable truss is only 1.5" thick while the top plate is 5.5" wide?

I was thinking I would basically build a triangle frame out of 2x4's that matches the inside pitch of 5/12 at the top, and then nail it along the top plate and shoot through the face of the gable truss studs into all three of the "plates" of the triangle frame all the way around.

But I haven't researched any of that just yet to see if there are better ways. I'm also not 100% sure how I'm going to build the inside walls so they go all the way up to the bottom of the trusses. I'm thinking it would be similar to the gable wall, essentially build an 8' wall, and then a triangle wall on top of it.

Is there a better way to approach it?


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## Nealtw (Jun 22, 2017)

timkoupe said:


> I think you're talking about the fact there is a 4" gap up at the top plate since the gable truss is only 1.5" thick while the top plate is 5.5" wide?
> 
> I was thinking I would basically build a triangle frame out of 2x4's that matches the inside pitch of 5/12 at the top, and then nail it along the top plate and shoot through the face of the gable truss studs into all three of the "plates" of the triangle frame all the way around.
> 
> ...


Your triangle idea will work, we never thought of that. :wink2: Put a 2x6 on top for drywall backing and that will reach the gable for nailing there.
We always build the interior walls before the trusses so we just add more on top like you are thinking. Then when you go up you put blocks between the trusses to nail the top plate to and they give you drywall backing, so you need a bock 24" in center for that.


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## DIYOkie (Jun 27, 2013)

On the porch columns...we were thinking maybe going with 4x6 treated. Then using doubled up treated 2x8's for the beams. 

The span is 5' and the span tables claim I only need one 2x8 so I'm thinking doubling them would be that much better. Don't we think of these beams as essentially headers? 

It's just not pretty to see sandwiched 2x8's....but I can't seem to find 4x8 or even 4x10 as you suggested...


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## Nealtw (Jun 22, 2017)

timkoupe said:


> On the porch columns...we were thinking maybe going with 4x6 treated. Then using doubled up treated 2x8's for the beams.
> 
> The span is 5' and the span tables claim I only need one 2x8 so I'm thinking doubling them would be that much better. Don't we think of these beams as essentially headers?
> 
> It's just not pretty to see sandwiched 2x8's....but I can't seem to find 4x8 or even 4x10 as you suggested...


Our beams get trimmed with nice looking wood that hides . And depending on how you finish soffit and the pitch of the roof.
It is hard to see in this picture but the soffit is level and hides the beam and then the ceiling in the porch is higher.


Yes full size timber would have to be special ordered. We have one yard that handles it and all the rest just buy from them.


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