How To Join Floor Joists

Believe it or not this kind of poor workmanship is not that uncommon.

How to join floor joists.

These problems must be addressed firsthand prior to implementing any restoration steps. This is unusual in new deck construction and would only be necessary for very long spans that exceed the length of your longest boards. If there was water damage make sure that whatever leaky pipe or condensation issue caused the rot is fixed. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall.

Tack a beam under the sagging joists. The new sister joist is cut to the same length or slightly shorter as the old joist and is inserted into the joist cavity and snugged up against the old joist. Sistering joists means beefing them up with additional material. Notches will compromise the strength of the new joists but some notches are acceptable depending on their location.

Maximum floor joist span for no. The longer the distance a joist spans without support the more it will flex. Here is a pathetic attempt to splice some floor joists under the bathroom. How to sister a floor joist.

The floor above will be stiffest if you place the wall in the middle of the joists. 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. Dead load weight of structure and fixed loads 10 lbs ft 2. But larger is not always better when builders are constructing a home or adding a room addition.

2 grade of douglas fir are indicated below. Live load is weight of furniture wind snow and more. 1 psf lb f ft 2 47 88 n m 2. Doing so strengthens weak joists and can help straighten sagging joists.

Drooping and joist sag can be seen in the photo. 1 ft 0 3048 m. By building a wall under joists you divide the span. Then set new joists same height as existing ones alongside the old.

Framing lumber is the typical. If you build a wall to support joists be sure to place a stud directly and tightly under each joist. Most often floor joists need to be sistered because of two problems either water damage which leads to rot or termite damage that crumbled the joist. 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.