I am looking to install some room in attic trusses on a garage I am building. The trusses provide a 13' wide room by the length of the building. In my case the room will be 13' x 28'. The floor of the bonus room is rated for 30 psf live load and 10 psf dead load. I will be sheeting the floor with 3/4" T & G osb. The ceiling below will be sheeted with 1/2" osb. I am looking to use the bonus room as a yard shed as it will be accessible from grade on one side. I am wondering what type of loads I can put up there. I plan to store common stuff like lawn furniture and kids bicycles up there but I am wondering if I could get my riding lawn mower up there or an ATV without having any issues.
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room in attic floor loading
- Thread starter burhead
- Start date
I spoke with one designer directly. I couldn't get a real straight answer but he finally said it would be fine. If you do the math, the total floor should me able to carry 11000 lbs and this is what he kept telling me. My concern is having 600 lbs in a concentrated area. If the ATV weighs 600 lbs and covers an area of 20 sq ft, that is right at the 30 PSF. I guess I'm kind of looking for some real world experience with these trusses. I am confident it isn't going to collapse but more concerned if it will cause sagging issues.
I spoke with one designer directly. I couldn't get a real straight answer but he finally said it would be fine. If you do the math, the total floor should me able to carry 11000 lbs and this is what he kept telling me. My concern is having 600 lbs in a concentrated area. If the ATV weighs 600 lbs and covers an area of 20 sq ft, that is right at the 30 PSF. I guess I'm kind of looking for some real world experience with these trusses. I am confident it isn't going to collapse but more concerned if it will cause sagging issues.
They should design it for 30 PSF AND 600lb point loads (or two 300lbs spaced apart 3') etc. Have them put that in writing.
ard
Well-known member
That 600lb ATV is 150lbs at 4 points, each prolly 1/2 sqft. Do the math. (It isn't quite that way as the plywood distributes the load, but still...)
What they TELL you on a phone call doesn't count for squat. Loose ****, lawn stuff, whatever is fine- but heavy rolling point loads would be cause for my concern. As above, you want it in writing.
What they TELL you on a phone call doesn't count for squat. Loose ****, lawn stuff, whatever is fine- but heavy rolling point loads would be cause for my concern. As above, you want it in writing.
Trey T
Well-known member
Your thinking is correct!I spoke with one designer directly. I couldn't get a real straight answer but he finally said it would be fine. If you do the math, the total floor should me able to carry 11000 lbs and this is what he kept telling me. My concern is having 600 lbs in a concentrated area. If the ATV weighs 600 lbs and covers an area of 20 sq ft, that is right at the 30 PSF. I guess I'm kind of looking for some real world experience with these trusses. I am confident it isn't going to collapse but more concerned if it will cause sagging issues.
not only a high concentrated load is a concern but the area where you place it can be the weakest point. The weakest point is what governs the ratings. Therefore, the ratings (dead or live load) allow users to place a load (not to exceed the ratings) any where on that floor and still be safe.
ard
Well-known member
Your thinking is correct!
not only a high concentrated load is a concern but the area where you place it can be the weakest point. The weakest point is what governs the ratings. Therefore, the ratings (dead or live load) allow users to place a load (not to exceed the ratings) any where on that floor and still be safe.
Not sure what you are saying....
What IS the sq ft load of a 600 lb ATV sitting on 4 wheels??
Trey T
Well-known member
take out your calculator or google it. I mean, you already formulated it already ... lol ... why are you asking? Either way, both loading will fail based on the designed rating of 10psf.
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bczygan
Well-known member
You are fine.
ard
Well-known member
take out your calculator or google it. I mean, you already formulated it already ... lol ... why are you asking? Either way, both loading will fail based on the designed rating of 10psf.
Im not looking for a fight or argument. ... I really didnt know which way you were leaning.
My question was aimed at how to determine how a load translates to a floor load- is it the tire patch? or something else. I was thinking that at some point the whole 'sqft load' thing breaks down- for example if a 100lb woman is standing on a single high heal, that can be 100lbs per 1/4" circle... 100lbs/0.04908 = 2,037 lb/sqft
But that is silly.
So I am guessing that for a floor assembly, with say 3/4" plywood floor, there is a rule of thumb for calculating how a point load would then be distributed to the floor assembly. Maybe something related to the joist spacing?
Sorry if this is degrading, was NOT my intent
bczygan
Well-known member
Im not looking for a fight or argument. ... I really didnt know which way you were leaning.
My question was aimed at how to determine how a load translates to a floor load- is it the tire patch? or something else. I was thinking that at some point the whole 'sqft load' thing breaks down- for example if a 100lb woman is standing on a single high heal, that can be 100lbs per 1/4" circle... 100lbs/0.04908 = 2,037 lb/sqft
But that is silly.
So I am guessing that for a floor assembly, with say 3/4" plywood floor, there is a rule of thumb for calculating how a point load would then be distributed to the floor assembly. Maybe something related to the joist spacing?
Sorry if this is degrading, was NOT my intent
You could do the math, but suffice it to say, using 3/4 T&G ply, glued and screwed, you're OK. I would keep joist spacing to 16"o.c. max. If you are really worried, instead of OSB for the ceiling under it, use plywood and screw and glue it. Make sure there is solid blocking at all joints and solid bridging at mid-span of joists. Loads will transfer.
Your ceiling isn't drywall, so L/240 is OK. Look here:
http://www.pfsteco.com/techtips/pdf/plywooddesignapplicationguide
Bill (Designer)
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BillK
Well-known member
My concern is having 600 lbs in a concentrated area. If the ATV weighs 600 lbs and covers an area of 20 sq ft, that is right at the 30 PSF..
Think about this. If four 150lb guys went into the room and stood in the same area as the ATV takes, do you think the floor would cave in ? Sort of doubt it. That's 600 lbs.
sublime68charger
Well-known member
As others have said you should be fine,
But for my own peace of mind I'd put down a 2x6 and park the atv or mower on top of that which will spread out the load of the atv or mower.
If really worried nail a 2x4 runner on edge to the inside or outside of the 2x6 to add more rigid holding power to the 2x6. You'll have a nice L bracket.
Just my thoughts.
But for my own peace of mind I'd put down a 2x6 and park the atv or mower on top of that which will spread out the load of the atv or mower.
If really worried nail a 2x4 runner on edge to the inside or outside of the 2x6 to add more rigid holding power to the 2x6. You'll have a nice L bracket.
Just my thoughts.