# Building Garage with Engineered Trusses



## twiles (Jul 2, 2008)

Hello all,
I am new to the site and looking for some help. I am building a 24 x 28 garage that has 9 foot walls and engineered trusses. The trusses have a room built into them that is 12 foot wide with7 foot walls that follow the pitch of the roof above the 7 foot mark. Here is my problem. I am trying to figure out the best way to frame in the stairway into the trusses. The stairs are being placed in the back of the garage on the back wall (24 foot). Option 1 - set all of the trusses 16" OC and cut the span boards after they are set and frame in the stairwell opening. Option 2- leave two trusses out, double up one truss (fasten two trusses together). The stairs are 48" wide which means there would be a 60" span between the last truss (one that is set on the rear wall) and the double truss located on the opposite side of the stairs. I would latter frame all the way around the truss every 16" OC with 2 x 8 boards 5 feet in length. The truss company says either method is acceptable however option 1 requires modification instructions from them (no big deal). The problem is my fatherinlaw says I am crazy for wanting to do option 2. This is why I am asking for your help. What is your advice? Which method is preferred or better? Thanks in advance.....
Twiles


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## Termite (Apr 13, 2008)

Welcome to the site.

So who managed to forget the minor detail of stairs??? :no:

I'd go with option number one, provided that your truss company will support you doing it. If they'll give you an engineered repair, that is the way to go. Just be sure you follow it to the letter. Engineered repairs for trusses are typically produced using MiTek or Alpine (or similar) software and engineering support, and they have tiny print and a lot of fine details. The details will include the nail size and spacing, sometimes glue, the exact materials to be used for the repair, etc. If they give you a fix, it is the way to go. 

Don't modify the design or the layout to get the opening width. You'll have to frame from truss to truss to get your floor and roof sheathing to span. Doubled trusses will often telegraph through the roofing materials as well...You might eventually see a bump, depending on the roofing.


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## twiles (Jul 2, 2008)

Kctermite,

Thanks for your response!!! The truss manf. did not listen when we called them to place the order and told them there would be stairs on the back wall. Also, when you order trusses that have a room built into them and you are placing trusses 16"OC that ought to send a big red flag up that says "this guy is going to need stairs". Anyway, the truss manf. is using MiTek software and I confirmed today that they will provide me with a repair procedure for modifying the trusses to frame in an area for the stairs. I was mostly confused about which option to use. I appreciate your advice! Thanks....
Twiles


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## Termite (Apr 13, 2008)

Sounds good to me. FOLLOW THE FIX TO THE LETTER. Small details make big differences with the reactions in trusses under load.


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## medeek (Jan 13, 2013)

*Stairwell with Engineered Attic Trusses.*

I've attached an image that shows a stairwell framed parallel to the trusses at one of the gable ends. The gable truss is designed to also be a load bearing truss over openings below so that is the reason for its complexity. If anyone has any suggestions on this I would be interested to hear them. The span of the trusses is 28 feet, 24" o/c.

My website does have a good 3D model of this sort of assembly (eDrawing) if it helps any.


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## AndyGump (Sep 26, 2010)

So let me guess, you are a truss designer and you are trolling building related talk sites to hawk your wares?

Andy.


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## Missouri Bound (Apr 9, 2011)

...and your website is swiss cheese.....:whistling2:


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## medeek (Jan 13, 2013)

AndyGump said:


> So let me guess, you are a truss designer and you are trolling building related talk sites to hawk your wares?
> 
> Andy.


Actually I design garages, sheds and other small residential structures on the side. I usually get BMC West to design my trusses once I have a floor plan established, I particularily like the Mitek software they use. It's too bad Mitek won't sell their softare to anyone except the truss plants, it would sure be helpful sometimes. 

The picture I posted shows how I dealt with the stairs coming up through the trusses. What I am curious to know is if there are better ways to do this or alternatives to what I have done. It seems to me that the best way to bring stairs through any floor or roof is generally run them parallel to the spanning members.

Its actually quite a compliment to be mistaken for a truss designer, I guess my drawings are pretty good. I just put up my website a couple of months ago and I am offering all of my plans for free (via PDF), I like the whole open source model and I think putting it all out there is the way of the future.


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## Maintenance 6 (Feb 26, 2008)

I sorta doubt that the OP is still waiting since July of 2008 for a solution.


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## medeek (Jan 13, 2013)

Maintenance 6 said:


> I sorta doubt that the OP is still waiting since July of 2008 for a solution.


Probably true but someone else will have the same question, I did.


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## mr leak (Dec 23, 2012)

*garage trusses*

The picture is commonly known as "truss laddering" also used when the truss company forgets a truss. Usually not a big deal and have the truss company stamp the ok at no charge It is no more than running the calcs thru their computer program NO CHARGE


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## medeek (Jan 13, 2013)

*Truss Designer*

I am a truss designer now... 

I've recently started working on a truss design software that will hopefully one day compete with the big boys out there. I'm still working on the plate and member sizing portions but so far I've pretty much got the geometry worked out for a number of common trusses. Here is a recent output from the CAD Generator (Fink Truss only for now):











Give it a whirl and tell me what you think. Remember it is still very much a work in progress:

http://design.medeek.com/calculator/calculator.pl


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## medeek (Jan 13, 2013)

Here is a sample output for the loads on a double fink truss:


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## medeek (Jan 13, 2013)

I've kind of hit a road block on the moment calculations. The current spec TPI 1-2007 calls for using the matrix method in determining the moments. However, I need to be able to run this app without doing a full blown analysis using RISA or some other FEA type product. For now I've gone with the simplified method which is the method used in the TPI 1-1995 standard, at least I can produce a solution. Typical result below:










If anyone has any ideas on how to do a simple matrix method analysis of a common fink truss please send me in the right direction. My biggest unknown with this would be how to deal with the fixity of joints at panel points and heels. I've just ordered a copy of Hibbeler's Structural Analysis to further research how best to deal with frames, trusses etc...

One thing I found really helpful was the samples provided in the previous editions of the TPI 1, its really quite disappointing to see no such example calculations in the current standard.


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## AndyGump (Sep 26, 2010)

I am going to keep this page as an example to everyone who asks me why engineering seems so expensive.
It is NOT expensive when you consider that it takes really smart guys (or gals) like this to work up a solution for their very specific situation.

I can't do it and am happy there are people who can.

Thank you MeDeek.

Andy.


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## Willie T (Jan 29, 2009)

Don't mean to nit-pick, but I honestly hope you are more careful with your calculations than you were with the proof-reading on that website.

I know you must have had the best of intentions, but a 5th grade teacher would tear you up on the mistakes and typos in that presentation.


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## medeek (Jan 13, 2013)

With a little help from a text called "Design of Wood Structures" by Donald E. Breyer and a recently purchased copy of the NDS 2012, the equations in TPI 1-2007 finally made a lot more sense (I was having some confusion with the bending effective length vs. the buckling effective lengths, combined bending and axial compression). I will say this has been quite an education with regards to structural design of wood structures. Last night I finally completed the full lumber analysis for the fink truss. Top and Bottom chords as well as all the webs. Now its time to start working on the heel joint check and all of the connector plates. Wind loads might be next but I need to research this quite a bit more. 

After doing some reading on trusses it seems that the simplified method of calculating moments should be fine for statically determinate common trusses such as a fink, howe, king or double fink truss. Its when you start trying to analyze the statically indeterminate variety (ie. attic trusses) then the simplified method really comes up short. For that I will need RISA integration with the app.


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## MTN REMODEL LLC (Sep 11, 2010)

Medeek...... Wish I could contribute... but basically it's over my head.... but darn interesting from a conceptual standpoint... to see just some of the calcs that go into a truss design.

THANKS

Peter


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## medeek (Jan 13, 2013)

*Lots of Calculations*

Actually it was a bit over my head initially when I first cracked open my copy of the TPI standard. I've never done a whole lot of structural engineering of wood so I had to become familiar with the equations and the process. However, once you step through it, member by member it does actually all make sense. My observations after digesting the bulk of the NDS manual is that wood engineering is all about "factors", loads and effective lengths. Then it is just a matter of plugging these factors and a few variables into the corrects equations for the given application and you either have a go or a no-go, its actually pretty simple.

With trusses, as is the same with beams and columns you make some assumptions then apply a number of checks in order to specify the lumber type and size. You start with a given lumber type/grade and then work your way up until it meets or exceeds all of the checks.


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## medeek (Jan 13, 2013)

*Oct. 2015 Updates*

I haven't posted about the truss designer for a while, apologies for that.

Still trying to improve it as time allows. The list of upgrades and improvements was getting rather lengthy so I've created a changelog page here:

http://design.medeek.com/calculator/changelog.html

Unfortunately, I had to put a daily limit on its usage because the server was getting hammered but it is still free to use.

The biggest improvement is the ability to specify the lumber grade, size and species as well as utilize point loads. This should make this tool far more useful for those wanting to check their roof for solar panel installations.

I'm still thinking about generating a 3d model for those wanting to import the truss directly into programs like Sketchup or REVIT

I appreciate all of the support I've received over the last couple of years on this project. Suggestions/feedback is always awesome.


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## medeek (Jan 13, 2013)

Added SketchUp 3D (.rb) file output for the truss geometry. This file, when copied into the SketchUp plugins folder, will create a menu item within SketchUp allowing for unlimited creation of the given truss geometry within SketchUp. I think this feature will be particularly interesting to those DIYers who wants to draw up their own model and plans using SketchUp.


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## medeek (Jan 13, 2013)

I've updated the code so that the plugin now allows for user input in order to specify number of trusses and spacing of the trusses. For example 4 trusses @ 24" o/c would give you:










The actual truss geometry cannot be altered within SketchUp it is hard coded into the plugin when it is created by the calculator. For different truss sizes and shapes it is simply a matter of creating and storing separate .rb files for them. Dropping these files into the SketchUp folder sets up the menu item. This method seems to be the easiest for interacting with the SketchUp API.


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## medeek (Jan 13, 2013)

*Attic Trusses created in SketchUp Plugin*

This is the same truss I used in my 28'x48' garage:










Now I need to work on the energy heel option for this truss as well as some additional logic for attic trusses in the following span ranges 16-24 feet and 30-36 feet.


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## medeek (Jan 13, 2013)

*Medeek Truss Plugin - 1.0.4*

Howe truss type is now active. 

The latest plugin version is 1.0.4. I would highly recommend downloading the latest version since I have also spent some time this morning cleaning up my code and removing global methods and variables so that I don't clash with other extensions or modules.


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## medeek (Jan 13, 2013)

*Scissor Trusses*










Version 1.0.5 - 10.24.2015
Added Scissor truss type, configurations: (2/2), (4/4).
Metric input enabled for scissor truss types.

In certain instances the scarf length of the bottom chord becomes less than the bearing length, the logic checks for these cases and inserts either a 3.5 or 5.5 heel wedge as required.


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## ront02769 (Nov 28, 2008)

Lot of work...but not really appropriate for this board. Read the guidelines. Ron


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## medeek (Jan 13, 2013)

I've got gable end trusses working for king post trusses:










I haven't made this latest update live just yet as I need to update all of the other truss types to make sure it does not break anything.

The other thing I am changing is the second user prompt box that allows one to enter in the number of trusses. I have now switched to a building length and the logic spaces the trusses based on the this length and the truss on center spacing. Gable end trusses can be switch on or off. Spacing of the gable studs is another user input.


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## medeek (Jan 13, 2013)

*Version 1.1.5* - 11.25.2015
- Added Double Fink common truss type.
- Structural outlookers (vert. & horz.) enabled under advanced roof options for Common (Double Fink) truss type.










For the DIYer a garage roof can be modeled in SketchUp within a matter or seconds. I also highly recommend the house builder plugin which is great for wall framing.


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## ront02769 (Nov 28, 2008)

Any chance you read the guidelines about not pushing your own crap on the. Board?.


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## medeek (Jan 13, 2013)

Another study of hip roof framing where unequal pitches meet at the hip. The birdsmouth cut is 3.5" for all jack and common rafters. The hip rafter is dropped and off center so that it lines up with the roof planes. The hip roof combines a 12:12 pitch with a 6:12 pitch.










View model here:

https://3dwarehouse.sketchup.com/model.html?id=uc12480ec-9330-464b-93eb-56bc73878207

Where the pitches are unequal like this it might make more sense to use a backed hip rafter rather than a dropped hip rafter. Does anyone have any suggestions or experience dealing with hip rafters that join unequal pitches?


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## Mingledtrash (Nov 27, 2015)

medeek said:


> Another study of hip roof framing where unequal pitches meet at the hip. The birdsmouth cut is 3.5" for all jack and common rafters. The hip rafter is dropped and off center so that it lines up with the roof planes. The hip roof combines a 12:12 pitch with a 6:12 pitch.
> 
> 
> View model here:
> ...


What do you need to know? your picture just shows hand stacked roof but that is far from how trusses are designed for this situation.









This is one way to do it. this way they just send out hip rafter board which we then cut to fit. another way is to actually make hip trusses instead of the hip rafter boards.










I dont really understand what you mean by a backed hip rafter.
Usually the truss designers are like you and dont know wtf to do so they just leave a big hole for us to fill in. are worried about the jack rafters not intersecting the hip at the same place. on the two different planes?


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