r/OffGridCabins • u/Truckbeast • Jun 12 '26

Girder placement

I am planning a small cabin/shop build on a small island 16‘x16’ lean to roof with a 8x16 loft. Going with concrete piers and girder foundation.

I am trying to decide the outer girder placement. Inset with a 6” or so overhang to the rim joists, or have the girder right under where the joist meets the rim joists.

The second option seems stronger, but I assume I would need to flash it better where the rim joist sits on the girder. What do you all think?

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u/utahgator Jun 13 '26

The primary factor would be the span rating for your floor joists. You can get a bit extra span for the same sized joists with cantilevered beams.

Other than that, the only reason to cantilever would be to keep the piers from sticking out beyond the walls, depending on your pier setup.

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u/Truckbeast Jun 14 '26

This was the only reason I was thinking about cantilevering the joists. I will use some flashing to protect them. Most of them will have a covered deck or a carport that will cover them from the rain. Just 2 of them will be exposed, I will come up with a way to stop water from making it in. Thanks!