Our gable-roofed block garage has a partial loft that we use for storage. I would like to finish the other half to expand useable attic/loft storage. There are 2x8-18 at 16” on center which span the space and rest on 10x10s at the top of the block walls and nailed to the rafters. Half is done every 16” and has a floor. The other half only has a joist every 4 feet and does not have a floor but those joists do have 2x4s nailed to them and up to the centerboard of the gable roof. There are ties horizontally between them in the center of the span for framing on the garage door track and opener. There are only 6 rafters without corresponding joists.

I am at a loss for finding 2x8-18 or 2x8-20 locally and do not have a vehicle that would allow me to travel a long distance and bring something so long home. I wonder if I can use 2x8-10 instead and Simpson tie them to the cross members that go in between the joists (that are also ties to the roof centerboard) instead of spanning the whole distance? The brace from the roof comes down every 4 feet. I need this secure enough to put 3/4” OSB as subfloor and store bins of off-season decorations, car roof storage box, and of course us walking up there to fetch things occasionally. Thoughts?

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    Pictures would be very useful here.
    – gnicko
    Jul 13, 2023 at 12:25
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    "The other half only has a joist every 4 feet and does not have a floor but those joists" -- these are not joists but rafter ties. They are not designed to carry load, but designed to be in tension and hold walls from falling outwards Jul 13, 2023 at 15:40

1 Answer 1


You have one good option, in my estimation. TJI joists. They'll need to be full span, so plan on delivery or truck rental. It's silly to compromise outcome for that reason.

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Talk to the lumber provider to determine size. I would think 9-1/2" would work for this. You may be able to go to 19.2" or 24" centers to save a few joists.

If you don't have enough space over your sill plate for their height, you may need to use strap hangers. These would fasten to the sill plate and fold down the face of the wall slightly.

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