What is the typical weight limit of an attic floor?

[DCal430]

I am thinking, around 250lbs a square foot?

 

[FoBoT]

do you mean a real floor, or where they just stapled down 1/4" plywood over the ceiling joists

 

[waggy]

do you mean a real floor, or where they just stapled down 1/4" plywood over the rafters

/this.



but..wtf are yo udoing that you need to worry about it?

 

[FoBoT]

yes, are you going to store some heavy things in an unfinished attic or just going up for an inspection?

 

[SNC]

I am thinking, around 250lbs a square foot?

There isn't one. It depends on the age the materials used, the distance between the supports, distance between the joists, thickness of the drywall/plaster..... There is a HUGE difference between a stick built structure and trusses. Most truss formed structures allow for very little weight to be placed on the horizontal elements. If you are not sure consult an engineer.

 

[Red Squirrel]

What are your intentions? If you want to build a livable space, you'll want to reinforce everything most likely. But if you just want to store some stuff or go do a one time job you should be fine. Just make sure that if you do store stuff, that you hang it off the rafters/trusses and not just put it right on the insulation or it will pack down the insulation overtime, reducing it's R value.

 

[DCal430]

Well I weight 275lbs, I am worried the floor will give in when I walk up there.

 

[FoBoT]

when i go up in an attic, i try to keep my feet over the ceiling joists, as i am a large person too
just in case
haven't done this, yet

 

[DCal430]

I just need to go up and change the bathroom fan/vent. I might just hire someone to do it, but seems like a job a person should do them self.

 

[FoBoT]

heck yeah, you can do that
i've changed those out. also installed ceiling fans in my Mo-in-law's house, had to cut holes and put in cross braces for the mounts

you'll be fine changing out a fan, just pay attention to where you are stepping, no worries

 

[OILFIELDTRASH]

Walk on the rafters. If you'd like to make it easier on yourself to move around up there nail some 1" thick plywood to the rafters. If there's already some 1/2" up there nail another layer of half inch on top of it. I nailed a crap load of plywood in my attic so I could store stuff up there.

 

[Dubb]

well, weight limit really isn't the right term. There are code-reguired design loads for various types of spaces, usually an allocation for dead load (the building and fixed things) and live load (people and furniture, things that can move around)

Design loads will be significantly less than the load that will cause unacceptable bending or failure (which is nearly impossible to know given all the variables and unknowns involved)

Design live loads will vary based on a number of factors, but at a minimum, 10 psf live load for attics without storage, 20 psf live load with limited storage, and 30 psf for habitable attics served with fixed stairs (International residential code 2009, older or local codes may be different)

 

[OILFIELDTRASH]

I weigh 185 and the half inch plywood was too flimsy for me.

 

[DCal430]

Ah ok, will try to change it out on my own next weekend then. thanks for answers.

 

[jagec]

well, weight limit really isn't the right term. There are code-reguired design loads for various types of spaces, usually an allocation for dead load (the building and fixed things) and live load (people and furniture, things that can move around)

Design loads will be significantly less than the load that will cause unacceptable bending or failure (which is nearly impossible to know given all the variables and unknowns involved)

Design live loads will vary based on a number of factors, but at a minimum, 10 psf live load for attics without storage, 20 psf live load with limited storage, and 30 psf for habitable attics served with fixed stairs (International residential code 2009, older or local codes may be different)

Or, put simply, as long as you walk on the rafters, and it's not the day after a 100-year storm dumped 37 feet of snow on your roof, you should be fine.

 

[velillen]

As others have said just stand on the rafters. I was up in my attic for the first real time today (running some wire for my antenna) and had no problem. Not sure how accessible getting plywood would be for you (i only had a ~2 foot x 2 foot access hole) but you can just get a 2x4 and lay it as a walking path across the rafters. i had two i did that way and moved em all over the attic as i worked.

But i also weight half as much as you. Just dont stand on the sheet rock itself. My access cover was just a piece and well its in two pieces now since i steped on it

 

[waggy]

As others have said just stand on the rafters. I was up in my attic for the first real time today (running some wire for my antenna) and had no problem. Not sure how accessible getting plywood would be for you (i only had a ~2 foot x 2 foot access hole) but you can just get a 2x4 and lay it as a walking path across the rafters. i had two i did that way and moved em all over the attic as i worked.

But i also weight half as much as you. Just dont stand on the sheet rock itself. My access cover was just a piece and well its in two pieces now since i steped on it

I looked at laying down plywood to make a storage area. get stuff i don't use and make room in the basement.

then i noticed the hatch is 2x2 hmm so much for that idea

 

[Greenman]

I am thinking, around 250lbs a square foot?

The floor system in most houses is designed for 40lbs per square foot. Ceilings are generally designed for little more than the weight of the finish material they have to support. All of them are figured in modulus of elasticity. Generally it's one 1/360 of the span.

 

[Greenman]

Or, put simply, as long as you walk on the rafters, and it's not the day after a 100-year storm dumped 37 feet of snow on your roof, you should be fine.

If you're walking on the rafters you're on top of the roof. You mean ceiling joists.

 

[Minerva]

when i go up in an attic, i try to keep my feet over the rafters, as i am a large person too
just in case
haven't done this, yet

hahahahaha!

You'd be surprised what the rafters can hold as far as walking goes. The ceiling will sag over time though if you put a lot of weight up there. Walking is fine just don't slip! (or walk on boards that are not nailed down or you may get slapped in the face and end up like the pic above!)

 

[jagec]

If you're walking on the rafters you're on top of the roof. You mean ceiling joists.

Err, you're right, I do.

<--has flat roof

 

[Howard]

Well I weight 275lbs

You won't have that problem in North Korea!

 

[iGas]

3/4" ply would work if you want use it as a walking plank, or a few 2x8s/2x4s, or what ever you have at hand.

 

[Kwatt]

I looked at laying down plywood to make a storage area. get stuff i don't use and make room in the basement.

then i noticed the hatch is 2x2 hmm so much for that idea

I had the same problem. I got lowes to cut 3/4 inch plywood into 3 ~ 16 inch wide strips.

Took it up and laid it out and nailed it down worked pretty good. Just need to get some more to finish it off.



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[feralkid]

I had the same problem. I got lowes to cut 3/4 inch plywood into 3 ~ 16 inch wide strips.

Took it up and laid it out and nailed it down worked pretty good. Just need to get some more to finish it off.



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Switch to Deckmate or similar grade screws; you'll actually strengthen the structure, whereas hammering nails beats it to hell.