Attic flooring options?

[SJMaye]

My garage is built with attic trusses on 24" centers. I want to use the attic are for general storage and trying to decide between plywood and Advantech OSB. The garage is a 24' wide open span. I have been worried about weight. The weight of Advantech and plywood appears similar. My concern about Advantech is that it is still OSB. My experience with OSB is over time it starts flaking of wood chips. Is Advantech different?

 

[mike93lx]

Advantech is much better than basic OSB. It's my first choice for subfloor and has worked great for the several projects I've used it on

 

[SJMaye]

I could see why Advantech could be a great subfloor which is subsequently covered with flooring. In my case it will not be. I would be interested in how the surface holds up after a few years. How has it been for you?

And do you know the weight different between it and plywood? as stated above, it appears to be similar. I am having a hard time believing that due to what appears to be a higher amount of glue content.

 

[mike93lx]

What are your trusses rated for in dead load?

Even if it was 10lbs per sheet more, that's a third of a pound per square foot and won't matter.

I wouldnt use it in a rough service area, but for an attic, it is absolutely fine. My current house has basic OSB in the attic and after 20 years, it is fine

 

[SJMaye]

What are your trusses rated for in dead load?

You had to ask. I am not sure how to read the truss drawings. Can you?

 

[mike93lx]

You had to ask. I am not sure how to read the truss drawings. Can you?

BCDL (bottom chord dead load) 10psf
BCLL (bottom chord live load) 20psf in the attic area.

the floor sheathing and the ceiling covering below, plus any insulation go to the DL. You and the stuff you have up there are live load

 

[SJMaye]

BCDL (bottom chord dead load) 10psf
BCLL (bottom chord live load) 20psf in the attic area.

the floor sheathing and the ceiling covering below, plus any insulation go to the DL. You and the stuff you have up there are live load

You don't know how much I appreciate you explaining that. Thank you.

I have no experience with trusses or attic trusses. Should I be worried about the weight of the subfloor? How can I tell if I am storing too much up there? I have nightmares of the ceiling falling in.

 

[mepstein]

I have osb in my house attic and use the room as an office. I also store Porsche parts in it. (It’s 44x18. Never any issues. I painted it with Porch paint to make it smooth and nice to walk on with socks or bare feet.

If you are worried, buy a piece of the osb, nail it 24” on center over some 2x4 on edge and test it out on the ground. Jump on it, stack some heavy items on it and get a comfort level for what you can do on it.

 

[mike93lx]

You don't know how much I appreciate you explaining that. Thank you.

I have no experience with trusses or attic trusses. Should I be worried about the weight of the subfloor? How can I tell if I am storing too much up there? I have nightmares of the ceiling falling in.

If the subfloor is 50lbs a sheet that is less than 2psf (50lb/32sq ft}. Drywall for the ceiling is that much again and insulation is a rounding error. So less than 4psf dead load.

If you put too much, the floor will deflect. I wouldn't store engine blocks up there or pallets of canned goods. But decorations, bins of clothes, etc are fine

 

[SJMaye]

Oh, I am not worried about the strength of the OSB. I feel certain it would be rigid and handle the span without much deflection. It's just not knowing how much is too much when storing up there. I shouldn't really worry. I wouldn't plan on storing anything really heavy anyway.

 

[SJMaye]

Mike, you have been a great help. Thank you for taking the time to answer my questions.

 

[mike93lx]

Anytime.

Those plans list higher loads as well in the notes. Not sure why that is and how it applies, but even at the lower levels that we have been discussing, you are good to go.

 

[firebirdparts]

20 pounds per square foot live load is is "light" but it's respectable. Just use restraint. Put the Christmas decorations up there, but maybe not a water heater, you know.

 

[Zen]

It's actually an additional 40 psf live load & 10 psf dead load at the attic area, see note #8

 

[mike93lx]

It's actually an additional 40 psf live load & 10 psf dead load at the attic area, see note #8

I did see that afterwards, but wasn't sure why they addressed the attic loading twice. Thanks for confirming

 

[nadogail]

I have had OSB in my garage attic for very possibly 35 years. I laid down carpet remnants to cushion my knees when I crawl around. The OSB has worked fine for a long time.