Garage attic floor loading

[FlaJunkie]

Questions for you construction guys out there.
My rafters are 24 in OC. The 2x4 trusses seem to be held together with metal plates.
Are these strong enough to put a floor over? Does anything need to be done to the truss bracing?

 

[70lt1z28]

Technically the truss system is designed to only support roof loads unless otherwise specified at design. Now with that disclaimer out of the way what it can really support is unknown. The usual home type stuff like Christmas decorations etc folks can get away with. Anything more than this and you are on your own. I had my attic over my garage trussed for 200 lbs per square foot load and the bottom crossbeam is a 2x8 and 16 OC. Distance between walls is also obviously important.

 

[FlaJunkie]

Technically the truss system is designed to only support roof loads unless otherwise specified at design. Now with that disclaimer out of the way what it can really support is unknown. The usual home type stuff like Christmas decorations etc folks can get away with. Anything more than this and you are on your own. I had my attic over my garage trussed for 200 lbs per square foot load and the bottom crossbeam is a 2x8 and 16 OC. Distance between walls is also obviously important.

Yeah, Christmas stuff isn't the issue. Yours sounds about right for average storage. I'll have to reconsider.

 

[Chevrolaine]

Depends how high you stack the bodies.

 

[Goodwrench1965]

Your question can be answered accurately by engineers who are consulted on questions like that every day selling that type component. Anyplace that sells wood roof trusses (Lowes, Home Depot, 84 Lumber) can give you number or call them for you. Obviously if you add conventional material like for example a 2x6 southern yellow pine along side of each truss bottom chord nailed 6 inches on center staggered and glued to the trusses spanned from the bearing wall to wall that will add significant strength. Add plywood on top and stagger the truss where the breaks in plywood are. Add a strong back 2x6 on edge nailed beside a laid flat 2x4 ( use all yellow pine no spruce or furr) perpendicular to the trusses on top of the plywood mid truss span. Put heaviest items closer to the bearing walls.

 

[smallblockchev]

The metal plates are called gussets, if you have a gusset where your plywood is going to lay, just sister a 2x4 on that cord and put on your plywood. And again don't store heavy items like engine blocks and trannys, if you stick to empty boxes and christmas trees you'll be just fine.

 

[Jim Streib]

In my garage when I first moved in back in 2001, the walls were not covered as well as the ceiling and being a 50+ year old house, the bottom of the roof trusses were sagging some BUT at least they were made out of 2x6 material with a span of about 18'.

I too wanted attic storage and new there would be limits and could not just put a floor down the middle and load it up.

So, what I did was between the top plate and the bottom sill, I married new 2x4's to the old 2x4's. I then placed new 18' long 2x6's above these new wall studs and then with a small jack under the few older boards that had sagged, jack them up in the middle to match to the new straight 2x6's and then married the new 2x6's to the old 2x6's.

I then had room to place 3/4" material on top just in the middle section of the attic from the front to rear. In one corner or towards the eave and the back wall of the garage I cut some more 3/4" plywood to use as a floor for extra storage. This extra storage was then used to house my compressor.

Fast forward to 2018, now 10+ years since I strengthened the ceiling joists/trusses with the added wall supports, I have had no drywall cracking issues, no sagging, and the center of the attic has been loaded with all kinds of parts without any issues.

Since I do not like how flimsy the pull down/fold out attic steps were, I designed my own attic steps and while they are no where near "code" as far as riser height to step depth, they work just fine for me and are not used a lot to where I just have to be careful using them.

On my pull down attic steps, I designed them using some large heavy duty hasp hinges along with a counter balance method using leftover bricks I found laying around the house, some all thread, some stranded steel cable, and some pulleys, to where now this 100 plus pound step assembly can easily be dropped down or put back up by one person and with one arm.

https://www.flickr.com/photos/[email protected]/albums/72157649311126315

Steps in down position:

Steps in up position:

Compressor at the top of the steps in the attic:

On the compressor, I extended the drain down to a petcock so I can easily drain the tank from inside the garage and not have to get into the attic and then put the compressor on a switched outlet controlled by a switch also down in the garage.

Jim