Recently moved and have been slowly getting the shop together in my garage. The house is a basic California 2-story built in 1977. Just two-thirds of the back wall of the garage is attached to the house and it has its own roof. That roof is held up by what I understand to be trusses made of 3/8" plywood and 2x4's. My brother-in-law knows a little about these things and tells me that the trusses are very good at holding weight up but aren't made to have anything stored "in them". I'd like to use the space for wood storage but I don't want the roof coming down.
He suggested that I couldn't even sheetrock the ceiling, the weight of the rock would be too great.
Contact your local building inspector's office and make an inquiry there. I had some business with these folks on occasion and saw contractors in there discussing beams and trusses with an inspector.
If it were a problem, you may (I am guessing) be able to reiforce the trusses to make them stronger. Again, check with the building inspector before doing this.
This is possible, but not likely. One would have to see the trusses to know. If I were you, I would find someone who knows more than your brother-in-law and have them look at it. If you can't find anyone else to ask, pose the question to your local building inspector. They are supposed to know these things.
Also, the way you describe the house, it seems to me that probably other houses in your neighborhood have the same or similar configuration. Go talk to your neighbors. (Good way to meet your new neighbors.) See what their experience is. Take a look at who is storing what in their garage and if anyone has had problems or if you can see any sagging. Draw on their quarter-century of experience.
That's true - in general the trusses are engineered to hold the roof up.
My entire house, albeit built in late 90's, is a trussed roof. The cieling is completely 'rocked.
Although I've walked on the trusses in my attic many times, I don't think I'd put anything very heavy on them without planks/plywood to distribute the weight.
True an engineer will tell you if this is OK. If you are going to load the trusses, the correct place to load them is at the points where the boards are attached to each other. Trusses are designed so that the elements are either in compression or tension (the force acts directly along the longitudinal axis of the members) as this gives the greatest strength for the least material. Loading the truss at other points causes bending which may reduce the compressive strength and therefore cause the truss to fail.
I'd think that you are fairly safe by sheet rocking them. And you are probably OK if you are storing light things like sleeping bags an the like, but you want to beef them up if you are storing stacks of lumber up there.
If it is an attic space I think it is recommended that you use a load of
10lbs per square foot and 20 if you are going to be storing things. Codes vary.
I don't know the details of the design, but he is essentially correct. Do you know the original builder or who made the trusses? They could give you a more definitive answer.
Trusses are used in a lot of house construction and they are sheetrocked, but they are designed to hold it. There may be some weight limitations with yours, but only the designer or an experienced, knowledgeable person can answer that. Ed
You have a simple truss system most likely. 2x4s are hardly recommended in general house construction and only used (usually) for storage sheds with very little (relative) dead load. I have a solution (Maybe): often 2x6 or 2x8 (depending on original design and usage) are recommended if you tend to use them as storage. I take it that your trusses are open in the garage. Take a 2x6 and add it along side the 2x4 truss cord, you may have to cut an angle to fit the ends under the roof line. The weight of the storage will now be stored on the 2x6 and not
2x4. How much can be stored depends on span (distance between walls) Type of wood (southern yellow pine or general white pine/spruce) and spacing (24" or 16" o.c.) If they sag you are nearing a limit. If you want an Idea as to dead load ratings of a 2x6, modern code often lists the specifications for various sized 2xs used for floor joists.
I looked at some new houses in the Houston area that have that type set up. The sales department said absolutely NOT for storage. I believed him when I looked at the attic pull down ladder that was heavily reinforced. The ladder was right next to the furnace and A/C unit. The water heater that is now normally put in the attics was on the ground floor.
Bottom line: I probably wouldn't worry about sheetrock, but would recommend storing significant amounts of lumber. Everything depends on the specific situation of course, after all trusses are used to carry all kinds of loads, but I'd think you'd find that most modern houses (last 20 years) use trusses for the roofing. For the trusses over the living space, there's sheetrock nailed to the undersides. That's my current and previous house and they're still standing. A lot of houses use trusses for the floor supports as well because you can have much greater spans than with solid lumber.
But it obviously depends on their design as to how much load they can carry.
Another sweeping generalization is that lumber storage would probably not be a great idea, as it is fairly heavy and you could get a pretty high load in a pretty small space. When I built my shop, which is in my basement, the inspector made me close in my ceiling so I wouldn't use the space between the joists (which were dimensional lumber) for lumber storage because he was concerned about overloading the joists.
If I recall, the general design load for decks (which probably is the same or close to that for interior home construction, and not applicable to roof trusses) that drives joist size, span and spacing is a 40# live load and a 100# dead load per square foot. I only know that because I had to provide a analysis with my deck to show the deflection in the joists & beams and acceptable footer loads with my planned (yet to be realized ... sigh) hot tub. A hot tub is a lot heavier than lumber, but that deck structure is far more massive than any house framing I've ever seen too. Not that helps, but may be of interest.
May not be relivant, but I built shelving into my attic trusses. I glued/screwed 2x4 supports into the V's, then screwed 3/4" thick solid pine boards to the 2x4s. I have maybe 200 lbs of stuff stored over five struss supports. Making triangles into the trusses will generally stiffen the truss and support the shelving. Wood can be rather heavy, depending on how much you want to store up there.
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