Sistering Roof Joists

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

Sistering roof joists.

Here s how we are correcting the problems. The most common way joists are repaired is to sister it up. With roofs this is done to improve the load value of rafters when installing roof mount air conditioning. Jacking them up too fast may cause cracks in the walls and floors overhead.

Our 60 year old floor joists are showing their age. 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. 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. If you want to upgrade to heavier slate or tile shingles or you decide to add dormers to the roof additional support is necessary. If the new sister bears on wood at least 1 5 on each end then you re good to go. If there was water damage make sure that whatever leaky pipe or condensation issue caused the rot is fixed.

The best case scenario is to run the sisters the entire length of the existing joists so that you have two additional resting points. Sistering joists means beefing them up with additional material. Sister refers to attaching an additional framing member alongside an existing member. If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists.

Framing lumber is the typical choice for sistering. In the case of 2x6 joists you can pair them up with additional 2x6 joists by nailing them together side by side. I forgot to mention the construction adhesive in between them. 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.

A day until they re level. Sistering is the process of adding a new joist next to each existing joist. The sloped rafters usually spaced at 16 inch intervals which is sufficient to support standard roof decking and shingles.