Adding On To Floor Joists

A neat trick contractors do when dealing with dry rot is add another level to the floor joists.

Adding on to floor joists.

Then refurnish the boards and add new boards to the affected part. After a lot of on line research i started seeing the same solution over and over adding to the bottoms of floor joists instead of sistering. The extra two inches of vertical distance when a floor is framed with 2 x 10 joists rather than 2 x 12s can be quite important for example. I read it doesn t need cross ventilation.

Notches will compromise the strength of the new joists but some notches are acceptable depending on their location. Measure the width and length of the existing joist. The best way to limit annoying flex in a floor is to make sure that joists are sized correctly before a house or addition is built. My crawlspace has six vents under the floor and i want to seal them up.

Even if your joists already have a row of bridging at the center of the span adding a row on each side of the existing bridging will stiffen the floor. This solution doesn t make the floor as stiff as the other solutions but since it s relatively easy and inexpensive you might want to try it first. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists. Building codes specify the minimum joist depth and spacing typically 12 or 16 inches on center for spans up to 20 feet but those requirements are intended to prevent plaster ceilings from cracking not to.

They put chemicals in the affected board to kill the dry rot. Most new construction uses 2 by 8 lumber for joists although 2 by 6. Sistering is the process of adding a new joist next to each existing joist. Then set new joists same height as existing ones alongside the old.

But larger is not always better when builders are constructing a home or adding a room addition. Tack a beam under the sagging joists. And i d like to know if i rip some inch plywood and sister it up against the 2x6s and glue and screw it if that would be sufficient. Purchase the type of lumber that matches the width of the existing joist.

To add a finishing touch paint the new boards if they don t match the other joists. Common sense tells you that large floor joists can carry more load and spacing joists closer together also increases the load bearing capacity of a floor. It s kind of old school. So i ve got 2 6 floor joists spanning 15 feet.