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Posted by Colbyt on February 7, 2010, 11:37 am
show/hide quoted text
>I am nearing completion of my attic project. I recently put in an
> attic stairs and putting in 3/4" OSB plywood for the floor, replacing
> the old T&G planks I had up there. I live in a split level 50 year old
> house. The attic is 2X6's spaced 16"OC. It spans approx 20' X20'.
> Below are some walls forming a bedroom closet .Although I am not sure
> if this is a load bearing wall for the attic, I would think it does
> add some support. But realistically how much weight can be put up
> there? Is there some sort of guidline?
Not very much according to my reference manual. A 2x6 16OC is only rated
for 30 live floor load to about 11'2". A 20 foot span 16" OC need at least
a 2x10 for a 30 pound live load.
For a 20 lb live load, limited storage with SYP joists 16" OC is good to
about 14.5 feet of span. This calculation includes the weight of a drywall
ceiling under the joists.
The good news is your old wood most likely is SYP and better than anything
you can buy today so I provided the ratings for Select Structural grade
instead of the lesser grades. I suspect you can exceed the numbers a little
with no real fears.
I would not fill it up and I would keep the heavy stuff to the sides. Sorry
to be the bearer of bad news.
--
Colbyt
Please come visit http://www.househomerepair.com
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Posted by Pete C. on February 7, 2010, 1:57 pm
Colbyt wrote:
show/hide quoted text
>
> >I am nearing completion of my attic project. I recently put in an
> > attic stairs and putting in 3/4" OSB plywood for the floor, replacing
> > the old T&G planks I had up there. I live in a split level 50 year old
> > house. The attic is 2X6's spaced 16"OC. It spans approx 20' X20'.
> > Below are some walls forming a bedroom closet .Although I am not sure
> > if this is a load bearing wall for the attic, I would think it does
> > add some support. But realistically how much weight can be put up
> > there? Is there some sort of guidline?
>
> Not very much according to my reference manual. A 2x6 16OC is only rated
> for 30 live floor load to about 11'2". A 20 foot span 16" OC need at least
> a 2x10 for a 30 pound live load.
>
> For a 20 lb live load, limited storage with SYP joists 16" OC is good to
> about 14.5 feet of span. This calculation includes the weight of a drywall
> ceiling under the joists.
>
> The good news is your old wood most likely is SYP and better than anything
> you can buy today so I provided the ratings for Select Structural grade
> instead of the lesser grades. I suspect you can exceed the numbers a little
> with no real fears.
>
> I would not fill it up and I would keep the heavy stuff to the sides. Sorry
> to be the bearer of bad news.
>
> --
> Colbyt
> Please come visit http://www.househomerepair.com
Those load specs are likely based on acceptable deflection under load
(L/360?) for comfort in a living space i.e. not too much bounce, not the
limit that will cause structural failure. Cracks in the ceiling
sheetrock are probably a greater risk than actual failure.
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Posted by Mikepier on February 7, 2010, 3:42 pm
I want to clarify, the entire attic is about 20X20, but the largest
span is 15 1/2' in my master bedroom then it rests on a wall that
creates the bathroom. all the other spans are 12' until hit rests on a
wall below, like the closet, bedroom wall, etc
I also heard it was good to screw down all the OSB to actually
strengthen the floor. So far it seems solid. I am not looking on
putting anything massive up there, just basic stuff.
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Posted by Steve B on February 7, 2010, 4:38 pm
show/hide quoted text
>>I am nearing completion of my attic project. I recently put in an
>> attic stairs and putting in 3/4" OSB plywood for the floor, replacing
>> the old T&G planks I had up there. I live in a split level 50 year old
>> house. The attic is 2X6's spaced 16"OC. It spans approx 20' X20'.
>> Below are some walls forming a bedroom closet .Although I am not sure
>> if this is a load bearing wall for the attic, I would think it does
>> add some support. But realistically how much weight can be put up
>> there? Is there some sort of guidline?
Very simple: put stuff up there until it crashes down. That's the limit.
3/4" plywood sounds a little heavy to me by itself.
Steve
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Posted by Harry L on February 9, 2010, 8:16 pm
On Sun, 7 Feb 2010 13:38:48 -0800, "Steve B"
show/hide quoted text
>>>I am nearing completion of my attic project. I recently put in an
>>> attic stairs and putting in 3/4" OSB plywood for the floor, replacing
>>> the old T&G planks I had up there. I live in a split level 50 year old
>>> house. The attic is 2X6's spaced 16"OC. It spans approx 20' X20'.
>>> Below are some walls forming a bedroom closet .Although I am not sure
>>> if this is a load bearing wall for the attic, I would think it does
>>> add some support. But realistically how much weight can be put up
>>> there? Is there some sort of guidline?
>Very simple: put stuff up there until it crashes down.
Then you put up less than that.
show/hide quoted text
> That's the limit.
>3/4" plywood sounds a little heavy to me by itself.
>Steve
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> attic stairs and putting in 3/4" OSB plywood for the floor, replacing
> the old T&G planks I had up there. I live in a split level 50 year old
> house. The attic is 2X6's spaced 16"OC. It spans approx 20' X20'.
> Below are some walls forming a bedroom closet .Although I am not sure
> if this is a load bearing wall for the attic, I would think it does
> add some support. But realistically how much weight can be put up
> there? Is there some sort of guidline?