Yet Another Garage Attic Load Capacity Storage Question?!?!?!?

[kwguinness]

So I recently moved into a new-to-me house that has an "attic" space above the garage. The previous owners framed in a 22.5"x30" opening and were using the space in the center for storage as there is currently 2-3 sheets of unsecured plywood laying across the bottom cord right in the center of the attic. I would like to use this space for light storage (famous last words). I have ordered a drop down ladder to access the space and will have to re-frame it to accommodate the 54" length (not a big deal). I have no idea how to calculate the load capacity and was hoping someone might be able to help. Any suggestions on how to reinforce it for a new subfloor would also be appreciated.

The attic is 25' Deep by 19 1/2" Wide and the truss system runs from front to back. The bottom cord is 2x6 24"OC and for some reason the bottom cord 2x6 are sistered with another 2x6 approximately 12' from the front of the garage and just stop. They do not continue the entire length of the garage. There is no center beam or support pole and unfortunately neither one is an option at this time. The attic uses a Standard Fink truss system, yet I don't know the pitch.

Here are some pics:

Back Wall to Web (7')


Web to Web (7'6")


Front Wall to Web (10'6")


Web (Unsure of Pitch)


Floor (2x6 24"OC)


The center is the most usable space, but I'm guessing the least stable. The roof is typical asphalt shingles over OSB and the web and cord are 2x4. I'm in Central NY so there will be snow on the roof a few months out of the year.

Am I asking for trouble using this space for light storage spread out?
(Christmas Decorations, Big Wheels, Kids Scooters, Camping Gear, etc)

 

[GMCGarage]

Unfortunately trusses are hard to figure capacity without expensive software. You should be good for 10psf at the max before you over stress the truss. In winter with snow loads will be your max loads.

A few boxes here and there is no big deal.

 

[kwguinness]

Unfortunately trusses are hard to figure capacity without expensive software. You should be good for 10psf at the max before you over stress the truss. In winter with snow loads will be your max loads.

A few boxes here and there is no big deal.

Any suggestions on a subfloor setup? I see a lot of people seem to run 2x4 perpendicular to the bottom cord and then fasten T&G subfloor to that. Any particular reason why you wouldn't just attach the subfloor to the bottom cord?

 

[6768rogues]

In NY it is commonplace for trusses to have a bottom chord dead load of 10 psf and no live load unless the original design specifically called for something else. The dead load is adequate to support a ceiling finish, lights and insulation. If you add anything else without some additional knowledge about the trusses, you could be asking for trouble.
That said, if you put stuff up there remember that you do not want to put too much weight up there and you do not want to put a concentrated load up there. If you put a couple sheets of plywood and a few boxes, not exceeding 10 psf, you should be ok. Plywood is only one or two lbs. per square foot depending on the thickness, so you could put a few light things on it, spreading the weight around.

 

[kwguinness]

In NY it is commonplace for trusses to have a bottom chord dead load of 10 psf and no live load unless the original design specifically called for something else. The dead load is adequate to support a ceiling finish, lights and insulation. If you add anything else without some additional knowledge about the trusses, you could be asking for trouble.
That said, if you put stuff up there remember that you do not want to put too much weight up there and you do not want to put a concentrated load up there. If you put a couple sheets of plywood and a few boxes, not exceeding 10 psf, you should be ok. Plywood is only one or two lbs. per square foot depending on the thickness, so you could put a few light things on it, spreading the weight around.

Thank you. The plan is to keep it light storage and spread out. I know everyone says that, but that is completely the plan. Nothing heavy will go up there. The garage ceiling is 5/8" fire rated sheet rock with 6 lights below as well as the garage door opener and garage door track. My plan was to lay 1/2 (19/36) OSB T&G subfloor perpendicular to the bottom cord. I know it will not be as strong as the area by the walls, but does doing it in the center of the web change things?

 

[GMCGarage]

Any suggestions on a subfloor setup? I see a lot of people seem to run 2x4 perpendicular to the bottom cord and then fasten T&G subfloor to that. Any particular reason why you wouldn't just attach the subfloor to the bottom cord?

Less is better. Just span over with 5/8 plywood. More lumber is gonna be less weight you can store.

 

[ard]

You might inspect each truss and see if there is any manufacture labels on them. If so, they can then look up the specs.

Howeevr, almost surely they are not rated for ANY kind of 'attic floor load'. By installing an access door and attaching flooring you may be creating a future issue when you sell and a home inspector accurately flags this as an 'unacceptable use'. Just FYI

If you do place any loads, keep it forward the walls, IMO. not centered in the truss...

 

[kwguinness]

You might inspect each truss and see if there is any manufacture labels on them. If so, they can then look up the specs.

Howeevr, almost surely they are not rated for ANY kind of 'attic floor load'. By installing an access door and attaching flooring you may be creating a future issue when you sell and a home inspector accurately flags this as an 'unacceptable use'. Just FYI

If you do place any loads, keep it forward the walls, IMO. not centered in the truss...

Thanks for the suggestion. I'll take a look.

As far as keeping loads by the wall, would you still do that if you hung one of those 4x8 metal storage racks from your ceiling? I haven't don't that, but have considered it. I'm leaning toward wall stud 24" deep shelving to minimize load on the truss system.


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[lakeroadster]

You've received good advice in regard to looking for data on the trusses themselves.

I'd suggest that you go to the city or county where you live and see if they have construction drawings on file for your home. If there are, see if there is a truss drawing. If there is look to see what the bottom chord loading is.

If none of that yields good results, contact a truss manufacturer, give them the dimensional data and they'll tell you what the allowable bottom chord loading is, but it may cost a few bucks.

 

[barks]

Drive around the neighborhood and witness all the garages that have collapsed, walls imploded and vehicles destroyed because homeowners used space above the ceiling for storage, light, heavy and in between. Post some photographs of the damage.

 

[ard]

Thanks for the suggestion. I'll take a look.

As far as keeping loads by the wall, would you still do that if you hung one of those 4x8 metal storage racks from your ceiling? I haven't don't that, but have considered it. I'm leaning toward wall stud 24" deep shelving to minimize load on the truss system.

Uggh
It's getting worse....



When you lay a 4x8 sheet of plywood on the 'floor' above the ceiling, you are roughly spreading whatever weight you put up there pover 32 sq ft. (Not really, but somewhat)

When you hang a 4x8 shelf, and have two corners where those are supported at ONE spot on ONE truss, the impact can be MUCH greater. Now half of that 32sq ft is loaded at one spot on each one.

If you take a 2x6, run it across all the truss bottom chords, then hang the shelf from that 2x6 (this is above the finished ceiling) at least the weight is being spred to all of them. This is a better approach with framing that can carry a load- your trusses are probably not desiged to carry much.

 

[GMCGarage]

Drive around the neighborhood and witness all the garages that have collapsed, walls imploded and vehicles destroyed because homeowners used space above the ceiling for storage, light, heavy and in between. Post some photographs of the damage.

Or be careful how much stuff you store up there so you dont collapse your roof.

Other non collapse issues are deflection. if you deflect your truss too much, drywall will start to crack. No big deal in a garage, but can happen.

Just because it hasnt happened, doesnt mean it cant. Ask those in Minneapolis.

 

[kelpaso1]

Drive around the neighborhood and witness all the garages that have collapsed, walls imploded and vehicles destroyed because homeowners used space above the ceiling for storage, light, heavy and in between. Post some photographs of the damage.

How many millions of homes have attics stuffed with so much ****. Plus a person or two walking/crawling also. Who hasn't thrown a 4x4 across a few rafters and hung a chain hoist and pulled an engine? I have never heard of someone overloading an attic to the point of collapse.

I'd say don't worry about it.

 

[kwguinness]

Uggh

It's getting worse....







When you lay a 4x8 sheet of plywood on the 'floor' above the ceiling, you are roughly spreading whatever weight you put up there pover 32 sq ft. (Not really, but somewhat)



When you hang a 4x8 shelf, and have two corners where those are supported at ONE spot on ONE truss, the impact can be MUCH greater. Now half of that 32sq ft is loaded at one spot on each one.



If you take a 2x6, run it across all the truss bottom chords, then hang the shelf from that 2x6 (this is above the finished ceiling) at least the weight is being spred to all of them. This is a better approach with framing that can carry a load- your trusses are probably not desiged to carry much.

Point taken.


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[TTTTTT]

When I had my 20x20 built I could have got typical trusses with a 2x4 bottom chord and very unusable space above. Contractor suggested trusses designed to give that 8' wide open space the entire length for a little extra $ They have a 6" bottom chord to give that extra for storage while still providing proper snow load specs. On 24" centre. Works great for lots of storage. Yours look similar.

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[Hot Rod Grampa]

We hung doors in a large subdivision. Attic stairs were cut in after final inspection by city. Contractor knew they were illegal, houses were designed for storage but regular trusses were cheaper. Will it work? Yes. But you may have to remove those stairs before you try to sell the place.