Double Up Floor Joists

Sister or double the ceiling joists with 2x6 s or 2x8 s with the ends resting on the wall top plates then lay the subfloor on the new joists.

Double up floor joists. Generally newer home floor joists are made from 2x8s or new engineered i beams older homes however may have 2x6s instead. Also take advantage of your extra materials by installing blocking around the perimeter. Double floor joists are two joists side by side that are usually nailed or screwed together along the length. I lay down some 1 2 or 3 4 ply when i m dealing with some old shabby pine tung and grove sub floors from the 1950 s its usually all split with big gapping gaps most of the time half the nails missed and the floors squeak all over the house i ll screw thru both layers into the joist makes.

You may want to install double rim joists across long sections to respond to the flexibility of the material. While it is a good idea to replace rotted material with 2x8s it may require some notching to fit between the sub floor and ledger board. Ive never heard of this making something stronger unless its finger jointed and bonded with epoxy unless its ok d by an engineer i would mess around with it personally. Doubling up wont double the span but it will increase the deflection rating and the ability to take more load on it.

Reinforce the joists and lay down a wood subfloor osb ply etc so i m not tiptoeing on joists whenever i m up there.