The section being inserted and sistered should be twice as long as the cantilever.
Sistered sistering floor joists.
This article provides step by step instructions and pictures on how to make structural repairs by sistering floor joists alongside weak joists.
So a 2 foot extension will be 4 feet sistered to the existing joist with appropriate fasteners 3 nails in a w pattern every 12.
Framing lumber is the typical.
Doing so strengthens weak joists and can help straighten sagging joists.
If you have sagging cracked or twisted joists which can happen in older houses this project will provide the extra support the floor needs.
How to sister a floor joist.
Since this is a repair of a faulty or damaged floor joist it is imperative to do this project correctly and there are a few big mistakes to avoid.