A question for the Engineers and Architects in the group

[Alpine 1789]

I know we have a bunch of engineers and at least a few architects in the club and I would like a non-binding opinion on garage attic storage. Had I thought of it in advance, when we had our garage built I would have specified roof trusses rated for storage. But I didn't and the ones we have are the now standard ones made from 2x4's that are attached together with metal joining plates. And of course, they come with a warning not to store anything in the attic.

The main (2 car) portion of my garage is about 20' x 20', with 9 ft ceilings. The bottoms of the trusses (e.g., the part that would be the attic floor, if I floored it) are made from a 12' 2x4 attached with joining plates to an 8' 2x4. I have avoided putting too much up there, but need more space for my S3 parts. The weak point seems to me like it would be the joint between the 12 foot and 8 foot pieces, so I screwed a 2x6 along the bottom of them, just to reinforce it (one screw on each side of the joint). I I have also taken a 5/8 piece of plywood, ripped it into 2 2X8 strips and made a floor/shelf for putting the S3 parts on. It is on the 8" side of the joist, so one side is supported by the wall. The other side is supported at two points by 2x4 reinforcements that go straight up from the lower piece to the upper piece (where the roof sits).

Hopefully, the above makes some sense. I don't plan on putting too much up there and certainly don't ever intend on walking around, but I suspect there will be multiple hundreds of pounds in parts spread out among the length of the 2x16' 'shelf' that I have now built. I know I should have sought advice before I started, but here I am.

So, how likely am I to come out one morning and find my garage roof sitting on the roof of my Alpine?

 

[alpine_64]

Jim,

Can you post a pic? If you are unsure see if you can find the "timber framing manual" online, it will give you a good idea of what you can/cant geta way with.

 

[jack Bacon]

a question for the engineers

Hi Jim,

Check out the forum on the garage journal forum -

http://www.garagejournal.com/forum/

They can provide a wealth of information. I have a 3 car garage with 2 X 4 trusses. They are definitely made strong enough to hold up a a 5/8" drywall ceiling and a pull down folding ladder. I installed 4' X 22' floor in the attic to hold all the light weight stuff like XMAS decorations, plastic garden pots, folding lawn chairs. Then insulated and drywalled the garage.

I believe Calfornia Car Cover in their catalog sells lightweight plastic attic floor tiles which is the best way to go to save weight

Regards,

JAck

 

[Ken Ellis]

Jim,
I would make wall mounted shelves that are securely attached to your (2x6?) walls, but which extend on legs to just above the level of the horizontal level of the trusses. This way the load is transmitted through the wall studs to the foundation, without putting any load on the trusses. This should be easier and safer than re-engineering trusses, especially in the absence of a truss engineer. Making two shelves, one above the floor level of the attic truss, and the other 18" or so below, would utilize the space way at the top of the wall. You'll need a ladder, but it'll be out of the way.

Check out Unistrut products and fittings, and perhaps Global Industrial Supply for modular industrial shelving. It'll be more expensive than the solution you mentioned, but cheaper than a new roof, new roof framing, and new cars and tools that were underneath it all.
Z-channel shelving from Home Depot is good, too. Car parts are really heavy.

We did engineered lumber, designed for normal live load (not just storage) on 24" centers... then built it on 16" centers, with tight blocking. Glued and screwed 3/4 flooring throughout, and then placed a 'strongback' -- an additional pair of 2x6 stringers in a "T" formation across the bottom of the floor joists. It doesn't move around much, that's for sure.

Ken
Non-engineer, non-architect.

 

[skywords]

Jim
I have a cheaply built garage as one can find, standard 2x4 trusses. I know very little about the design of these things. I needed to lift my Alpine body on to the rotisserie so I put two beams across four of the trusses and lifted the car with no problem using come alongs. FWIW

 

[Alpine 1789]

Thanks Guys. I'll post some pictures tonight of what I have and also check out the links. ...and hold off unpacking the S3 for a little longer (it still has all of the parts in the tub and boot from when Steve, Ray and I packed it up in Dallas).

 

[RootesRich]

Jim,
Most 2x4 trusses, like the ones you describe in your attic have a bottom chord designed to resist a maximum of 10#'s psf live load and 10#'s psf dead load.
I'd stay away from storing anything heavy (like a tranny up there). Wheels, doors, a complete axle should be fine. Just keep the loads distributed evenly and spaced apart across the area.

Rich Vose, Registered Architect