Will roof trusses support attic floor okay?

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Old 03-05-08, 08:02 PM
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Will roof trusses support attic floor okay?

I want to make use of my attic space for storage and would like to install a pull down stairs for access. I have a roof truss system on 24" centers and can install the stairs parallel witht he trusses with no problem. I'd like to add some plywood sheets for light storage, (holiday decorations and stuiff like that). My question is should I have concern with weight on the lower part of the roof truss from adding plywood and stored things? I'm not so concerned with the weight of things that will be stored as much as am the weight of a person that will be on the attic floor to get the the stored things. Should I have any concern with this?

FYI- my house is a basic rectangle with a single gable, (shaped like a barn, two roof surfaces only) so my roof trusses span the entire 40' width of my house. Its a two story and there is a support wall that runs the entire length of the house on the second floor dividing the house in half. So the attic entry would be at the center of the house under the main gable, which is directly over the support wall.

Appreciate any advice. I've read a lot thats its okay to add attic stairs with roof trusses, but I havent read anything that indicates its not okay to add light weight items within reason with an attic floor as I would like to do.

Visser
 
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Old 03-06-08, 04:46 AM
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hate to think,,,

how much static weight's in our attic over the garage,,, enuff that i've gotta replace the pull-downs,,, you should be fine.
 
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Old 03-06-08, 05:47 AM
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Cool

if you have trusses and the access hole is next to the center supporting wall you will have no problem as long as you don't get carried away with the storage. don't store any heavy metal or large heavy objects. spread out the load. remember, the truss is a SUPPORTING structure and not a CARRYING structure. it it there to support the ROOF!
 
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Old 03-06-08, 06:44 AM
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also don't skimp...you'll want to use 3/4" plywood or osb. If the bottom chord of those trusses are 2x4 (probably are), I wouldn't store anything too intense up there as mikeTN reiterated.
 
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Old 03-06-08, 07:04 AM
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Attic

I think you will need horizontal framing attached to the truss chords to allow for adequate insulation between the attic floor and the ceiling below.
 
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Old 03-06-08, 12:08 PM
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Thanks to all of you for responding. Everything mentioned makes sense and I was thinking the same way, but helps to have some additional good advice.

Wirepuller38 brings up a good point. The attic already has loose insulation that is about 14" deep. If I clear a small area of the attic to put down plywood for storage, I'll only have as much insulation as the 2" x 4" truss construction will alow between the attic floor and the ceiling below. Wondering if I should indeed consider what sounds like a great suggestion in adding horizontal framing to increase the thickness of the insulation under the part of the attic that has floor, or if I need to worry about it since I'm not flooring the whole attic space.
 
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Old 03-07-08, 08:49 AM
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First question: are the trusses designed to carry this load?

Some are, some are not - a truss is designed to carry loads applied in specified directions at specified locations and can be subject to failure if (relatively) small loads are applied in some other manner.

If you don't know if these were intended to support the dead and live loads of flooring the attic and using it for storage, you need to verify this with the truss manufacturer. If you can't, have an architect, engineer or other qualified person verify that the truss can carry this sort of load:

2006 IRC - R802.10.4 Alterations to trusses. ... alterations resulting in the addition of load ... that exceeds the design load for the truss shall not be permitted without verification that the truss is capable of supporting such additional loading.
 
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Old 03-08-08, 07:40 AM
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notwithstanding ANY of the other comments,,,

we've had 3-ply 1/2" up there for 35yrs & no deflections yet from Christmas stuff, saddles, suitcases, hi-school yrbooks, etc,,, if insulation's a concern, place 1 layer of ply, some 4x8 sheets of polystyrene board, & another layer of ply for a wearing surface on top.

ours is over a garage therefore insulation's not a concern to me.
 
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