Sistering Roof Joists

These problems must be addressed firsthand prior to implementing any restoration steps.

Sistering roof joists.

Sistering the beams or rafters is one way of adding structural support to the roof. A day until they re level. In the case of 2x6 joists you can pair them up with additional 2x6 joists by nailing them together side by side. If there was water damage make sure that whatever leaky pipe or condensation issue caused the rot is fixed.

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. Sistering is the process of adding a new joist next to each existing joist. With roofs this is done to improve the load value of rafters when installing roof mount air conditioning. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists.

I forgot to mention the construction adhesive in between them. The sloped rafters usually spaced at 16 inch intervals which is sufficient to support standard roof decking and shingles. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall. Jacking them up too fast may cause cracks in the walls and floors overhead.

The best case scenario is to run the sisters the entire length of the existing joists so that you have two additional resting points. Here s how we are correcting the problems. Framing lumber is the typical choice for sistering. Doing so strengthens weak joists and can help straighten sagging joists.

Sister refers to attaching an additional framing member alongside an existing member. Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. 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. Essentially sliding a whole member beside it and nail the heck out of it from both sides with a lot of nails.

Our 60 year old floor joists are showing their age. Sistering joists means beefing them up with additional material. Since this isn t a floor then the allowable deflection tables don t really apply adds jigs n fixtures.