# Attic catwalk design



## Hogan773 (Aug 22, 2012)

Hi all - I'm a new poster here. 

I am about to get cellulose and air sealing in the attic. I'd like to build a simple catwalk that would allow me to get access to the side of the HVAC trunk system in case I need to access it to check for leaks etc in the future. I want to do this before the floor gets 8-ish inches of cellulose. 

I have 2x6 rafters on 16 inch spacing in the attic now, with R-19 batts stuffed in between. 

I was originally thinking a simple design with some 2x6 pieces, stood upward (so 5" height) and laid across 2 rafters perpendicular, then a plywood deck on top. But 2 problems....1) this only gives me 5 extra inches and I really need 8+. Second problem is there are sections of conduit, the HVAC supply and return ducts, etc all around too, so it makes it more challenging to get clean even spacing.

Now I'm thinking about cutting 8 or 10 inch lengths of 2x4, standing them up on the 2x6 rafter, attaching them to same so they make "posts" and then running horizontal 2x2s or 2x4s to make a "top rail" that sits on those posts, and then throwing a plywood deck on top to walk on. 

Questions for the experts on here

1) are there problems with my design? I realize that by standing up 2x4s I'll be loading the rafter but I figure that the existing rafters have already been holding my 180 pound weight directly as I've been walking on them, and the "rail" connecting along the tops would act as a beam and distribute the weight among several 2x4 posts.

2) What is the best method to "stand" the 2x4s up on the 2x6 horizontal chords? Should I use a metal L-brackets at the corner between them, or some sort straight metal bracket down the side that screws into the side of the 2x6 and the 2x4? Or a plywood gusset on one side? I'm trying to envision whether there are risks that the standing 2x4 post "slips off" the 2x6 it's sitting on one side or the other, or whether I should be worried about the 2x4 rotating and falling down. I'd think when the top rail is attached the risk of any single post rotating forward is small, but one would want to make sure that the whole thing wasn't able to shift sideways so that it "falls off the rails" and into my ceiling.

Or would it be better to take 16" sections of 2x4 and attach them across the posts to make "arches" and then lay a 1x10 board down the middle of those arches? I don't really need 16 inches width of catwalk I guess. How far could I get the spacing of those arches....24".....30"? 

I realize that I'm trying to articulate what is in my head so it might not be clear.....

any advice from you guys would be appreciated - thanks


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## GBrackins (Apr 26, 2012)

why not run 2x6 joists on top of existing joists, perpendicular to the existing ceiling/attic joists at 12" to 16" o.c. and put your decking on top of that. It would provide you with about 11" of insulation and would be more stable that a bunch of "posts".

of course you would first need to do an analysis to determine if the existing 2x6 joists could support the imposed loads of someone walking around. your post does not indicate the spans of the joists. check out this link from the 2009 International Residential Code (basis for most building codes in United States) for spans of ceiling/attic joists.

http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_5_par020.htm

your existing ceiling/attic floor system may not have been designed for people to be up there, plus do not know where your load being walls are below (if any) in relationship to your walkway. If the existing joists cannot handle the load you'll be looking at cracks in your ceiling (at minimum).

just my humble ramblings ....


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## Hogan773 (Aug 22, 2012)

GBrackins said:


> why not run 2x6 joists on top of existing joists, perpendicular to the existing ceiling/attic joists at 12" to 16" o.c. and put your decking on top of that. It would provide you with about 11" of insulation and would be more stable that a bunch of "posts".
> 
> of course you would first need to do an analysis to determine if the existing 2x6 joists could support the imposed loads of someone walking around. your post does not indicate the spans of the joists. check out this link from the 2009 International Residential Code (basis for most building codes in United States) for spans of ceiling/attic joists.
> 
> ...


 
Thanks for the input....I realize my original post was long and convoluted but basically your idea was my first idea but I scrapped it because it won't be high enough AND the location of various conduits and ducts makes it harder to get nice even spacing across the existing joists.

They are planning to add 8 inches of cellulose and the current fiberglass is even with or extends above the existing 2x6 joists, so putting another 2x6 perpendicular just adds 5 inches of new space. It will be buried when they're finished blowing.

I agree re: existing loading but I have been in the attic many times before, as have some others, walking carefully along the 2x6s and they've held fine. I'm not planning on storing anything on this catwalk.....just walking.


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## kwikfishron (Mar 11, 2010)

Not sure how old your duct work is but if it was me I’d be spending “cat walk funds” on inspecting, repairing or updating the ducts (or anything else) before it all gets buried.


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## GBrackins (Apr 26, 2012)

use a 2x8 with 3/4" plywood sheathing ..... 7-1/4" + 3/4" = 8"

or stick with the 2x6 with 3/4" = 5 1/4" + 3/4" = 6" and tell them not to cover the walkway


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## GBrackins (Apr 26, 2012)

kwikfishron said:


> Not sure how old your duct work is but if it was me I’d be spending “cat walk funds” on inspecting, repairing or updating the ducts (or anything else) before it all gets buried.


I agree ..... :thumbsup:

make sure to insulate the ductwork with R-8 insulation minimum (check with your local codes, could require more) and make sure they are sealed. don't want leakage into a "cold" space. creates all kinds of issues


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## Hogan773 (Aug 22, 2012)

kwikfishron said:


> Not sure how old your duct work is but if it was me I’d be spending “cat walk funds” on inspecting, repairing or updating the ducts (or anything else) before it all gets buried.


I already checked myself and there are just a couple noticeable leaks. One is where a duct came apart from the trunk and is about 1/2 inch. A few others are small. I'm going to go up this weekend with some mastic and tape and play.


The contractor will be doing air sealing so they'll be boxing can lights, foaming cracks, etc before blowing.



GBrackins said:


> I agree ..... :thumbsup:
> 
> make sure to insulate the ductwork with R-8 insulation minimum (check with your local codes, could require more) and make sure they are sealed. don't want leakage into a "cold" space. creates all kinds of issues


My home was built in 2004 and all the ducts are already wrapped tight with R 4.2. Beyond fixing obvious leaks, I'm not sure how practical it is to re-wrap or over-wrap all the ducts to get to R-8. (Is R-8 even the requirement?) At Menards and HD here they sell 6.9 duct wrap. 

I can seal some leaks myself but it doesn't seem worth it to pay an HVAC contractor $1000 or more to add R-3 or 4 to my ductwork.....there are quite a few ducts. Most of the ductwork will be mostly or fully covered in cellulose too at the end of this job which will add to their R-value I'd think. Just the main trunk will be above. I wonder if there is an easy way for me to wrap some new insulation around the trunk only....maybe just laying pieces of foil pipe wrap across and foil taping on top of the existing foil wrap that covers it now. I guess even if I get 85% of it wrapped up with another layer, that would make it better, no?


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## GBrackins (Apr 26, 2012)

My comment on R-8 insulation for ducts is based upon the 2009 International Energy Conservation Code by the International Code Council, your code may differ. Check out this link for their requirements

http://publicecodes.cyberregs.com/icod/iecc/2009/icod_iecc_2009_4_sec003.htm

Just make sure you use HVAC tape (metal foil) not duct tape ...... any reduction in leakage and increase in insulation is a good thing

Good luck!


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## Hogan773 (Aug 22, 2012)

GBrackins said:


> My comment on R-8 insulation for ducts is based upon the 2009 International Energy Conservation Code by the International Code Council, your code may differ. Check out this link for their requirements
> 
> http://publicecodes.cyberregs.com/icod/iecc/2009/icod_iecc_2009_4_sec003.htm
> 
> ...


 
Thanks. My question on the duct insulation is - when the A/C was running full bore if I place my hand on the top of the insulation, I don't feel any "cold" sensation. Therefore is there really a benefit to adding another layer of foil insulation on top if I am just going to be insulating something that isn't cold as it is? (I mean the cool temperature of the duct is staying inside the current insulation)

EDIT: I googled and came up with this http://ducts.lbl.gov/distribution.html#insulation

While I can't view the graph on PC, the text basically says that there are fast diminishing returns to higher amounts of duct insulation.


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## GBrackins (Apr 26, 2012)

I couldn't tell you if you'd save money or not by installing more insulation around the ducts or not. I'd spend my time and efforts in sealing them so there are no leaks and see what happens

I was just stating where my R-8 suggestion came from ..... here we don't have any choice, if your ducts are outside of conditioned space they must be insulated to a minimum of R-8.

Good luck! :thumbsup:


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## Hogan773 (Aug 22, 2012)

GBrackins said:


> I couldn't tell you if you'd save money or not by installing more insulation around the ducts or not. I'd spend my time and efforts in sealing them so there are no leaks and see what happens
> 
> I was just stating where my R-8 suggestion came from ..... here we don't have any choice, if your ducts are outside of conditioned space they must be insulated to a minimum of R-8.
> 
> Good luck! :thumbsup:


Thanks....I wish I had R-8 but the code must have been different when my home was built. That was only 8 yrs ago....I guess things change quickly!

Much of the runs will be sitting in cellulose so I'll certainly get some extra kick there. I'll just focus on the leaks at the trunk since I can't really feel any leaks along the runs, and they're all sealed up with continuous insulation wrap (one piece). There also some spots where there is just foil tape at the junction of the trunk and the duct...ie the foil tape is taping the insulation down on the metal duct and where the foil is the only thing on the duct metal, if you put your hand on it it is cold. So I may try to wrap some extra material around those unions to avoid thermal losses there. Probably not nearly as bad as an actual air leak in terms of performance though, I am assuming.


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## Gary in WA (Mar 11, 2009)

With R-8, you would be losing about 10% of the heat/cold air to the attic. If the main trunk is surrounded/under the cellulose by 50%, about 5% loss; pp.2, convert from R-3.6 per inch; http://www.enersavesystems.com/pdf/Economic-Thickness-of-Thermal-Insulation.pdf

Add plywood sides around the trunk for complete coverage of cellulose. Be careful not to exceed the weight limit of the drywall; http://www.energyguide.com/library/EnergyLibraryTopic.asp?bid=austin&prd=10&TID=17324&SubjectID=8375

Check locally, some HVAC catwalks require 16-24". Keep in mind it should be plywood, not OSB (molds easier) in my opinion. Drill 2" air holes @ 6" to vent the cellulose to the attic air. The fiberglass will be compressed 1-2" by the cellulose, increasing it's density for a higher R-value per inch. Add solid blocking between the new joists every 5-6' and the joints/ends to prevent rotation. Leave the top off for insulation install, have them lay them in place loosely (to walk on) as they back out while applying. Screw the new joists to every old joist, perpendicular and centered over a bearing wall. If possible, wire some new lighting up there beforehand to get a premium job. Vacuum the existing loose-fill from the soffits before they add plastic baffles (with a wind-washing protection over the exterior wall) to reach 12" above the new blow-in, which also keep the soffit empty of insulation; http://www.bergerbuildingproducts.com/productsAccuvent.html

http://www.owenscorning.com/around/ventilation/pdfs/VentSure.pdf

Gary
P.S. where are you located, we can figure your insulation needs....


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## Hogan773 (Aug 22, 2012)

GBR in WA said:


> With R-8, you would be losing about 10% of the heat/cold air to the attic. If the main trunk is surrounded/under the cellulose by 50%, about 5% loss; pp.2, convert from R-3.6 per inch; http://www.enersavesystems.com/pdf/Economic-Thickness-of-Thermal-Insulation.pdf
> 
> Add plywood sides around the trunk for complete coverage of cellulose. Be careful not to exceed the weight limit of the drywall; http://www.energyguide.com/library/EnergyLibraryTopic.asp?bid=austin&prd=10&TID=17324&SubjectID=8375
> 
> ...


 
Wow - thanks for all that good info.

My supply trunk is on the bottom and the return trunk is directly on top. This should be a good thing as it makes it easier to "bury" the supply side under the cellulose, and the return trunk sort of insulates it from the top.

Not sure how I'm gonna build a plywood box since there are 4 ducts coming off one side and several on the other....I'll ask the contractors what they can do.

I've already got 2 light sockets up there so I'm probably OK there.

When you say I might need 16" or 24" what do you mean....width I assume? Or distance between my new joists/arches? 

Is there really a code for attic catwalks when nobody can stop me from tiptoeing down the joists as I do currently? I mean there probably is a code for everything...I'm just wondering when something like an attic catwalk would be enforced in reality. Probably only if/when we sold the house I'd think.

Can you envision my "arches" plan to support the catwalk and does it make sense? I'm thinking of standing 8 or 10 inch lengths of 2x4 on end, attaching them to the top of the existing joist with an angle bracket, then putting a 2x4 across the top perpendicular to the existing joists. Basically a variation on the idea others mentioned about just laying down 2x6s across the joists, but would allow me to build HIGHER without the added weight of trying to stand up 2x8s or 2x10s which are heavy. It only needs to hold my weight and I'd think a 2x4 "arch" spanning only 16 inches should not have any issue with normal human's weight, especially because the plank above would beam the weight across multiple arches.. I am thinking the angle brackets should help avoid any tendancy for the posts to move side to side or fore and aft. I might be crazy though. My guess is it will work fine, but I'm wondering if the engineers out there would tell me I'm not doing it correctly.

Thanks to this thread I'm getting some good ideas. I never really thought about burying the trunk in cellulose until this thread....


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## tony.g (Apr 15, 2012)

............


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## hand drive (Apr 21, 2012)

I've built cat walks in attics and it is usually best and most simple to build a 2x10 cat walk 16 to 24" wide with a few 2x10 spacer blocks about every 4'. A cat walk I did recently had the same situation with insulation already in the attic and the insulators were on the way to do blow in for the entire attic. We built the catwalk and insulated inside of it with r 30 before putting the plywood on top, that way when the insulators came we did not have to go back into the attic space to put down the plywood afterwards.


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## Hogan773 (Aug 22, 2012)

tony.g said:


> ............


That's an awesome drawing....thanks!

I am not a carpenter but I take it that you're suggesting the 2x2 strips on the inside is basically making a gusset design which is more secure than my idea of using some 1.5x1.5 metal framing brackets (L-bracket) at the topside of the original joist where the 2x4 post would sit. I can get metal L-brackets for 50 cents each and they accept 2 screws on each face. I thought that might be simpler and would sufficiently keep the 8" post from moving on top of the joist.


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## tony.g (Apr 15, 2012)

You can use 1.5" x 1.5" brackets to secure the 'posts' to the top of the existing ceiling joists, but presumably you would also need some to fix the top rails to the posts. You would be fixing these from underneath, which would be difficult to get to.
If I've read correctly and the brackets are 1 1/2", tbh that is not very big and the screw fixings will be small and close together - i'm not sure that would give you a good, firm fixing. 
If the brackets are 50c each, and assuming you used 4 per 'post' (ie 2 at the top and 2 at the bottom), I wonder if a few 8ft lengths of 2x2 might work out cheaper, and they would probably give you a firmer fixing as well.
The main point to watch is lateral movement - you don't want the structure lozenging sideways - that's why i suggested a few plywood pieces going across the assembly, screwed to the posts and a tight fit between the ceiling joists.
(i'm not into HVAC so don't know about the other bits! good luck with it).


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## Hogan773 (Aug 22, 2012)

hand drive said:


> I've built cat walks in attics and it is usually best and most simple to build a 2x10 cat walk 16 to 24" wide with a few 2x10 spacer blocks about every 4'. A cat walk I did recently had the same situation with insulation already in the attic and the insulators were on the way to do blow in for the entire attic. We built the catwalk and insulated inside of it with r 30 before putting the plywood on top, that way when the insulators came we did not have to go back into the attic space to put down the plywood afterwards.


So you're saying just 16 to 24" pieces of 2x10, laid perpendicular to the existing joists. *Do you fasten the 2x10s with metal L-brackets to the top of the joist?*

Reason I had devised this 2x4 "arches" design was because my gut was the extra weight of the 2x10 pieces might be a bad thing. So I should have taken pen to paper earlier......I just googled weights per foot and I basicaly calculate that a 18" section (I'd think that should be fine to sit perp to 16" OC joists) of 2x10 is approx 5 pounds while my "arch" made of 2x4s is 3.8 pounds. That doesn't count the various screws needed to fasten together the 3 piece arch vs a single solid piece of 2x10....probably nomimal but the deck screws aren't weightless either. 

Ok so basically I over-thunk it! I can't imagine that an extra pound on each riser is going to kill my ceiling over time, given that this is a limited catwalk and not a full attic floor build. 

Sorry to keep asking questions but I enjoy learning about this stuff too and want to do the right thing

1) did you use plywood deck on top of the rafters or can I just use 2 1x8s? 

*EDIT:* I did the calc and I can get 24 linear feet of 5/8" plywood deck from one 4'x8' sheet and it would cost $15 if I get OSB Sturdifloor or $20 if I get CDX plywood. For 24 linear feet I'd need 6 1x8 boards which would cost $38. So the cost is almost 2X - there's my answer. 1x8 pine board is a tad thicker but I'd assume 5/8" plywood is sufficiently strong for my needs. Can I get by with 1/2" OSB or CDX or is that going to be too bendy? Or do I need to go 3/4" OSB or ply? I'm lost on what the various "span ratings" etc mean in practice for a 180 pound person walking on a catwalk.....

2) can I get by with 30" or even 36" spacing between the 2x10 risers? I have a single 1x8 board in my garage and I stood on it last night....I weigh 180 pounds and it felt very solid with 30" spacing between blocks underneath it. I don't want to over-spec this with 2x10 pieces every foot or whatever because while that would certainly be stable and I could drive a truck on it, I'm adding extra materials cost and dead weight with each 5 pound riser that is unnecessary....

Unfortunately I prob can't finish and insulate the catwalk before the guys come because they are doing air sealing and they'll need to get at some conduit protrusions as well as some can lights and I don't want to finalize something that is then somehow in their way. I'm thinking I'll just install the risers and then they can blow the stuff around, then I'll come back and add the top deck.


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## tony.g (Apr 15, 2012)

If you are putting 2x10s across the ceiling joists, you would bigger/stiffer brackets than 1.5" to keep them vertical.


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## hand drive (Apr 21, 2012)

Hogan773 said:


> So you're saying just 16 to 24" pieces of 2x10, laid perpendicular to the existing joists. *Do you fasten the 2x10s with metal L-brackets to the top of the joist?*
> 
> Reason I had devised this 2x4 "arches" design was because my gut was the extra weight of the 2x10 pieces might be a bad thing. So I should have taken pen to paper earlier......I just googled weights per foot and I basicaly calculate that a 18" section (I'd think that should be fine to sit perp to 16" OC joists) of 2x10 is approx 5 pounds while my "arch" made of 2x4s is 3.8 pounds. That doesn't count the various screws needed to fasten together the 3 piece arch vs a single solid piece of 2x10....probably nomimal but the deck screws aren't weightless either.
> 
> ...



the 2x10 would be side runners of undetermined length as of yet and is determined by how easily you can access the attic space with the lumber. you could start with 8' stock for the runners.The runners will go perpendicular to the joists or diagonal or parallel. The 16" or 24" spacer blocks ( depending how wide you make the walkway) are laid out at 2' or 4' centers in between the two side runners creating a ladder of sorts and you want these spacer blocks to land where the seams in the plywood are, hence the 2 or 4 foot increments. with your walkway you want to emulate how the joist system looks and is built, imagine one of the joist bays with blocks turned upright and spaced every 2' and then take that and set it up on top of the joists, that is what your walkway will look like.

For the 16" walkway you can basically build directly in line and on top of the ceiling joists that are there and once you have the ladder framed the walkway will hold its own structure, you simply need to attach a few vertical blocks ( as mentioned in other parts of this thread) to tie the ladder to the existing joists. if you build it across the joists, perpendicular or diagonal the same holds true, the ladder will hold its own structure and will only need to be tacked down to the ceiling joists.

with spacer blocks spaced 2' along the ladder 1/2" osb is plenty strong for the catwalk...

that will be fine to let them get it insulated and then you come back last and deck it.


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## Hogan773 (Aug 22, 2012)

Great - thanks. I need to get back up there tonight to have a look. In theory what you're saying makes a lot of sense but in practice it might not be that simple because I'll be spanning various HVAC ducts as well as some metal electrical conduit runs. I'm thinking it won't be as simple as just laying down my "ladder" on the floor and tacking it down. I might have to either just stand up 2x10 pieces with metal brackets or another thought just popped into my head.....making "H's" which would basically be sections of 2x10 sitting parallel on top of the joist with a 16" piece perp across the inside attaching them together........I could throw down an "H" in between each duct (the catwalk is going to be parallel to the HVAC trunk and therefore stepping over several ducts that are coming off it at 90 degree angles). Then I could tack down the OSB flooring across the Hs provided that the distance between the "runner" part of each H doesn't leave too much gap for the OSB to sag down. Maybe I'd go with a 5/8 or 3/4 OSB instead of 1/2 just to keep the sagging to a minimum. Gotta go stand on some OSB at the lumberyard to see how much it really deflects.

The benefit to doing "Hs" is then I don't rely on metal brackets to stand up the 2x10s vertically.....the H does it and I'd just need something to make sure the H can't move laterally off the joists that it's sitting on. Just angle a screw diagonally at the bottom where it sits, or do I need some bracket or side gusset?

*One more question for since you're a carpenter.....I've read to use Deck Screws for something like this. If I'm working with 2x10s non-pressure-treated and OSB can I just screw them in straight or do I need to pre-drill holes? Will a pine 2x10 split from a screw without a pilot hole? *


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## hand drive (Apr 21, 2012)

Hogan773 said:


> Great - thanks. I need to get back up there tonight to have a look. In theory what you're saying makes a lot of sense but in practice it might not be that simple because I'll be spanning various HVAC ducts as well as some metal electrical conduit runs. I'm thinking it won't be as simple as just laying down my "ladder" on the floor and tacking it down. I might have to either just stand up 2x10 pieces with metal brackets or another thought just popped into my head.....making "H's" which would basically be sections of 2x10 sitting parallel on top of the joist with a 16" piece perp across the inside attaching them together........I could throw down an "H" in between each duct (the catwalk is going to be parallel to the HVAC trunk and therefore stepping over several ducts that are coming off it at 90 degree angles). Then I could tack down the OSB flooring across the Hs provided that the distance between the "runner" part of each H doesn't leave too much gap for the OSB to sag down. Maybe I'd go with a 5/8 or 3/4 OSB instead of 1/2 just to keep the sagging to a minimum. Gotta go stand on some OSB at the lumberyard to see how much it really deflects.
> 
> The benefit to doing "Hs" is then I don't rely on metal brackets to stand up the 2x10s vertically.....the H does it and I'd just need something to make sure the H can't move laterally off the joists that it's sitting on. Just angle a screw diagonally at the bottom where it sits, or do I need some bracket or side gusset?
> 
> *One more question for since you're a carpenter.....I've read to use Deck Screws for something like this. If I'm working with 2x10s non-pressure-treated and OSB can I just screw them in straight or do I need to pre-drill holes? Will a pine 2x10 split from a screw without a pilot hole? *


The H blocks are the idea and/or a full box (rectangle) might be even better to give support at the very ends. Also consider a 2x4 set flat on the top upper edges that could span the walkway across the ducting( the plywood wood go on top of the flat 2x4's). Also if the walkway is built correctly it can turn corners and even branch off, anything to fit the space. Vertical 2x4 bracing connecting walkway to joists at or near all outside corners and spaced out evenly along the longer spans would work good to hold the walkway in place. 

pre drilling for screws is not necessary for framing but will help if you have a hard time at getting screws to set without camout. I recommend the deck screws that have the star drive tips( 3" for framing) , any screw length over 2" with a Phillips tip will likely strip out without predrilling. I use the star drive for any type of framing usually. 
Also consider construction adhesive at the connecting points in the framing.


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## Hogan773 (Aug 22, 2012)

hand drive said:


> The H blocks are the idea and/or a full box (rectangle) might be even better to give support at the very ends. Also consider a 2x4 set flat on the top upper edges that could span the walkway across the ducting( the plywood wood go on top of the flat 2x4's). Also if the walkway is built correctly it can turn corners and even branch off, anything to fit the space. Vertical 2x4 bracing connecting walkway to joists at or near all outside corners and spaced out evenly along the longer spans would work good to hold the walkway in place.
> 
> pre drilling for screws is not necessary for framing but will help if you have a hard time at getting screws to set without camout. I recommend the deck screws that have the star drive tips( 3" for framing) , any screw length over 2" with a Phillips tip will likely strip out without predrilling. I use the star drive for any type of framing usually.
> Also consider construction adhesive at the connecting points in the framing.


Excellent thanks

I assume "construction adhesive" is something more robust than Elmers Wood Glue......probably something in caulk tube?

The funny thing is, once I complete this project I'll probably never use the walkway since I don't really store anything up there! But I think it's prudent to leave a path over to the A/C trunk area just in case I need to do more leak sealing or something. My actual HVAC unit is encased in a special room up there that is already easily accessible at the top of the stair, and there won't be cellulose right over there.

Thanks for the steer on the star drive....I never would have known to look for that.


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## hand drive (Apr 21, 2012)

I'm really glad to help. Yes, construction adhesive caulk may not be needed though,(your choice) if 3" screws in framing and 3"screws through the decking into the framing is used.


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## Hogan773 (Aug 22, 2012)

Uggh. I just went up to the attic again to draw and measure. There all kinds of electrical conduits going everywhere at angles, and about 2 inches above the joists. In a few places it's hard to really find a way to lay out the 2x10s. Could perhaps measure and notch them to fit over.

I'm now rationalizing that I might not really venture into this space at all except for emergencies and so why am I building the Golden Gate Bridge in one specific area of the attic? I mean I'm leaving 90% of the attic untouched yet I'm building a solid 2x10 catwalk along a single stretch? If I ever really needed to, I can step into 8 inches of cellulose or rake it aside. Wondering if maybe the lazy man's way is to cut some pieces of OSB or plywood and just tack them down on top of the rafters in the area I MIGHT walk in in said emergency, and then let them blow the cellulose on top. That would provide a safe way to step through the cellulose without trying to divine where the rafters are and should eliminate the sight of my foot sticking through the ceiling! 

I dunno - think I'm probably tired so need to sleep on it and maybe I'll feel re-energized for the original challenge tomorrow.

Anyway, thanks again for all the helpful advice. In any case I'll be up there tomorrow with some mastic and foil tape to address a few leaks I found along the trunk where the ducts attach. Fun stuff!


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## tylernt (Jul 5, 2012)

Hogan773 I wouldn't step through the cellulose onto OSB on the joists. The cellulose will be compacted and lose insulating value. Similar thing happened in my old house, 12" of fiberglass and 2x6 joists. There was a trail running the length of the attic where everyone walked and the 'glass was visibly compressed and less efficient. 

I'm in the same boat as you now BTW. However I only need to add 6" of insulation to my new house, and my catwalk would go perpendicular to the joists. I was thinking of standing up a 2x6 and using hurricane ties to attach it to the joists, but after looking at tony.g's drawing I could stabilize the 2x6 with 2x2 "posts" cheaper (the ties are 40 to 80 cents a pop).

Once I have the 2x6 secured, I'll just nail a 2x4 flat across the top of that for a walking surface. Maybe a 2x6 if I want luxury. Hey this is a catwalk, not an interstate freeway. 

I'm sure I'll have to notch for wires and such, probably just take a recip saw or rotozip with me to the attic and hack where necessary without measuring. It won't look pretty, but the new insulation will hide that.


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## Hogan773 (Aug 22, 2012)

Yeah I hear you.....like I said it was late and I was tired and thinking "why am I really going to go buy lumber, screws etc and build this thing when I probably won't walk up in the attic in the next 5 years. As my furnace is already accessible and will remain so, the only reason I'd be going elsewhere is to check the HVAC trunk for air leaks (which I'll be doing now before the insulation) or if there is an emergency like a roof leak or something.

I thought that I COULD step through cellulose and/or sort of rake it to the side a little, and for $5.99 a bag if I was really concerned I could carry a bag up there and dump more in if it is "compressed" at some point in the future. One $5.99 bag claims to cover 40 sqft to R-19 depth. 

Trip to Menards later today and I'll see what I end up buying there! Maybe I'll just stand up a few 2x10s in clean spots and then lay a 2x6 or 2x8 across the span and just bridge over all the conduit and ducts. I need to see how strong a 2x8 is when I go to the store but I'm guessing that I could easily span 4 or 5 feet sections if I needed to and not have it flex excessively on my 180 pound weight. Again, just for emergencies. 

The reason I was hesitating is because I am not going to build a full catwalk across the *whole attic floor* that gets me everywhere I'd ever need to conceivably go, so I questioned the value of building a Golden Gate Bridge catwalk in one specific section......just figured it might be slightly more likely I'd want to access the HVAC distribution trunk at some point, but I don't know whether that is once every 2 years or once every 5. 

Now onto another question.....bathroom vents exhausting to the roof. I may post that elsewhere if this isn't the right forum.


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## tylernt (Jul 5, 2012)

Hogan773 said:


> Trip to Menards later today and I'll see what I end up buying there! Maybe I'll just stand up a few 2x10s in clean spots and then lay a 2x6 or 2x8 across the span and just bridge over all the conduit and ducts. I need to see how strong a 2x8 is when I go to the store but I'm guessing that I could easily span 4 or 5 feet sections if I needed to and not have it flex excessively on my 180 pound weight.


I have a 2x12, 8ft long, that I use as a motorcycle ramp. A 400lb motorcycle with about 200lb on each tire, it sags a little but not a scary sag by any means. I'm sure an engineer would shudder at the thought but I wouldn't be too worried about a 2x8 placed flat and supported at 4ft intervals holding up a 180lb guy, the weakness is in the joints and fasteners. As you step mid-span, the 2x8 will bow and pull the supports toward you under bending stress. Ensure the supports are reinforced against bending and you should be good.

Note, I am not an engineer...


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## Hogan773 (Aug 22, 2012)

Yeah I have a *1*x10 pine board that is my "helper" in certain situations......I've used it to slide a 200 lb generator in shipping crate out the back of my minivan and down to the ground....just slide down the board.

My guess is I could probably stand in the middle of an 8 foot span of 2x8 with no intermediate piers and it would still be fine......obviously the more piers the better though to distribute weight and reduce bending, as you said. And no I'm not an engineer either! (as if that wasn't already obvious)


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## tony.g (Apr 15, 2012)

Hogan773 said:


> My guess is I could probably stand in the middle of an 8 foot span of 2x8 with no intermediate piers and it would still be fine....


In theory, it wouldn't work. A 180lbs weight in the middle of a 2x8 (probably actually 1.5" x 7.5") would produce a bending stress of about 1500lbs/sq.in. Most commerciially available softwoods have a max. permissible stress of 800- 1200 lbs/sq.in.
So while in theory it would snap, here on planet earth it won't because of the safety factors built-in to the figures. (it would bend a lot, though!).


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## Hogan773 (Aug 22, 2012)

So as an update, I went ahead and did the catwalk rather than wussing out and throwing down plywood to walk on later. Glad I did because I like the result, and I learned a few things about projects like this.

If I can figure out how to post a picture I will, but basically there are 2 sections....1 section is a 10 ft straight run that is parallel to the existing joists. For that, I used 18" lengths of 2x10, stood up perpendicular to the existing joists, and then used pieces of 2x4 attached at the very top in between each to keep them from flexing back and forth. For the top plank I am going to put down a single 10ft length of 2x10. I found 4 acceptable spots for my vertical risers and they are generally 36-40" apart. Yes, may be stretching it in theory but with the 2x4 brace and the single 2x10 on top, it is super solid in reality. In fact I can stand in the middle of just the 2x4 piece and it is rock solid even if I bounce up and down a little. That is just butted in between the risers and double screwed with #9 3 1/8 in screws.

For the second section it turns a corner so I basically constructed 2 "boxes" which consist of 2x10 sides connected with short lengths of 2x4. The 2x10 deck will bridge from box to box, landing on them like piers, with the second leg attaching to a large existing truss that runs across the whole attic and is already raised off the floor.

What I learned:

On the original section I used 4" right angle brackets to initially stand up the risers, before I added the 2x4 butting in between. For the boxes, they were much smaller and compact and stand up on their own, so instead of wasting a bracket I just used a 45 degree screw into the joist underneath on each corner. Seems to hold it down just fine.

Thanks to this forum I learned about TORX drive screws. Thanks! I already had a box of driver bits that I had bought on impulse once when they were on super sale at Menards, and luckily there are several T25 bits in there. They worked well and I was able to drive in 3 1/8 screws without any pre-drilling. Just make sure you're leaning into the drill so it doesn't slip. One of my bits got chewed up about 3/4 through the project so I had to toss it and use a second one. Perhaps because they are cheapo Stanley bits that I got on super sale, or maybe that is just the nature of the beast. If I were building a whole deck or doing lots of work, I can see going through several bits in a day (or spending money to buy stronger bits if that is an option).

I also learned to be creative, envision the project, draw it out and measure carefully. by the time I made it to the boxes I had the full design of those in my mind and actually built them in the garage where it was easy to saw, screw, etc. Doing so in the attic would have been more risky. I just carried the boxes up to the attic, set them on the joists and screwed them down. When they fit perfectly it was a great feeling.

I also learned that when you're doing the 45 degree screwdowns, it's easier to take a drill and pre-drill the hole to the angle you want, and also to pre-drill the screw all the way till it's just poking out. Then when you set it down you have 4 screws, all sitting there looking at you, and all you have to do is buzz them down 1, 2, 3, 4. 

While my design may not be "engineered" to the official specs, I have no doubt that it is plenty solid and strong to withhold a 300 pound man let alone my 180 pounds. 

Glad I did it myself because for <$50 in materials, plus some time, I was able to build something that works well and fits exactly in the areas I wanted it to go. I have a sense that if I asked the insulation contractor to do it it would have cost many hundreds of dollars (since they value their time at a much higher cost) and might have been something they hastily tacked down, and which I might have always looked at and regretted.


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## tylernt (Jul 5, 2012)

Thanks for coming back to post the results! Glad it went well. It will pay off the first time you have a tradesman up there to do work and he compliments you on your sweet attic. 

After you've copied the pics to your computer somewhere, when you reply to this, scroll down a bit and a ways below the 'Submit Reply' button you should see an 'Additional Options' section with a 'Manage Attachments' button. From there you can Browse to the pics.


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