Garage Attic Storage

[Lee Ludden]

My shop is an attached two car garage. The attic area is just wasted space, so I'd like to make better use of it, and I'd like some feedback.
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This is what my truss looks like (in black). They are standard 2x4 premade truss on 24" centers. I plan on adding a cross member (red) at a height such that there is 24" on each side of the vertical member. Then put down 1/2" OSB on tops of those cross members as well as across the tops of the bottom of the truss, and then use that area for storage (the yellow boxes). I'll be using plastic storage containers and plan to hold mostly high bulk, low weight items, but there will probably be 600-800 pounds total weight spread over the entire area. The total size of the garage is about 22x22. Am I asking for trouble or should this be pretty safe?

[John M Wilson]

Am I asking for trouble or should this be pretty safe?

One potential problem I can see is the loads on the crossbars of the truss. These members are intended to be in compression, transmitting the roof load to the bottom rail of the truss. Your middle section (the beam in red) will put a bending stress on these members - pushing them out of a straight line, and drastically reducing their ability to transmit the roof load to the bottom of the truss.

Now, most structures have quite a bit of safety factor built in, and you may never see any problems. However, in my opinion (and although I am a mechanical engineer, I am not a structural engineer) you are asking the truss to do something it was not designed to do, and that is the definition of asking for trouble.

Trusses are designed & sized to hold up the roof, and to a lesser extent, hold up your ceiling sheetrock. Modern construction techniques are aiming for the maximum performance with the minimum of lumber, and structures are not overbuilt like the "good old days".

You might get lucky, but I'd be wary...

Good Luck!

[Ole Anderson]

You could beef them up by sistering a 2x6 along length of the bottom chord and running a short 2x4 vertically up to the truss web, where your proposed horizontal member will be.

My attic access is through a drop down stairway in the mudroom and the ceiling is drywalled in the adjoining garage. The contractor installed Howe (K) trusses, which makes the area mostly inaccessible. I had him modify most of them to a modified Fink (W) style by going with a 2x6 bottom chord, eliminating the vertical post and revising the angled truss web. It still isn't a stand up attic, but I floored the central portion, installed a few bare bulb lights and carpeted it so it wasn't so hard on my knees when crawling around for the Christmas decorations. 37 years now.

http://jonestruss.com/pdf/jbs_trusstypes.pdf

[Norris Randall]

"600-800 pounds total weight spread over the entire area"
800 total would equal approx. 3 pounds/ sq.ft

I do not think you would have any problem if the quote is accurate.
I'd use screws to add the cross members NOT nails.


Or if you are still concerned check with the truss builder in the area.

[Myk Rian]

I took everything I could out of my garage trusses, and built a shed to store it all.
Especially my wood supply, which is now on 2x4 brackets I built on one wall of the shed.
Sheet goods are stored on edge in the shed.

If you must use it for storage, keep the weight as far to the outsides as you can.