Sistering Roof Joists

If the new sister bears on wood at least 1 5 on each end then you re good to go.

Sistering roof joists.

A day until they re level. I forgot to mention the construction adhesive in between them. The most common way joists are repaired is to sister it up. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall.

Since this isn t a floor then the allowable deflection tables don t really apply adds jigs n fixtures. Framing lumber is the typical choice for sistering. Here s how we are correcting the problems. The sloped rafters usually spaced at 16 inch intervals which is sufficient to support standard roof decking and shingles.

Sister refers to attaching an additional framing member alongside an existing member. Sistering joists means beefing them up with additional material. The best case scenario is to run the sisters the entire length of the existing joists so that you have two additional resting points. Essentially sliding a whole member beside it and nail the heck out of it from both sides with a lot of nails.

The sag could be reduced or eliminated by installing king posts or leom could sister 2x8s to the 2 6 joists to roughly triple the load bearing capacity of the ceiling. Jacking them up too fast may cause cracks in the walls and floors overhead. With roofs this is done to improve the load value of rafters when installing roof mount air conditioning. 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.

In the case of 2x6 joists you can pair them up with additional 2x6 joists by nailing them together side by side. Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. If there was water damage make sure that whatever leaky pipe or condensation issue caused the rot is fixed. Doing so strengthens weak joists and can help straighten sagging joists.

Sistering the beams or rafters is one way of adding structural support to the roof. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists. Our 60 year old floor joists are showing their age.