Considering an extension, I'm planning to make my own floor joists and would like some opinions on them.
For the floor joists, I plan to use 2 pieces of 2" x 4", one at the top and one at the bottom, with approximately 12mm OSB board between the studs (on both sides).
The floor joist should be about 33cm high, and I'll insulate the floor with sawdust. Then there will be boards with underfloor heating on the joists.
I'm considering painting the underside of the joists (facing the ground) with tar.
How long will these joists last?
