How To Sister Attic Floor Joists

The existing ceiling joists are 2x6s clear spanning about 11 feet 3 inches.

How to sister attic floor joists.

On both sides of the problem area. When joists spacings are wider they should be deeper as well to limit stress and deflection under the load. Sistering is the process of adding a new joist next to each existing joist. The floor framework is mostly made of wood joints running parallel to one another at regular intervals.

Most floor joists are typically spaced 2 by 8s 2 by 10s and 2 by 12s. I need to convert an attic to livable space with minimal disruption to first floor habitation. In the case of 2x6 joists you can pair them up with additional 2x6 joists by nailing them together side by side. Depending on the existing attic structure a contractor might be able to sister the current joists by attaching new joists of the same dimension beside them.

Rather than sistering in deeper members which would involve moving wiring can i stack new 2x6s on top of the existing ones. In situations when sistering damaged floor joists with lumber of similar dimensions it can be easy to notch and slide the sister board into place. However doing this does not fix the slant that the floor has taken since the old joists got damaged. New homes install i beam shaped joists.

If the attic joists are not adequate one way to strengthen the floor for live loads is to sister the old joists. Jacking them up too fast may cause cracks in the walls and floors overhead.