How To Sister A Roof Joist

If only a few joists are rotted primarily at the bottom they can be repaired using a process known as sistering after the rot is cleaned away and the timber treated to prevent more problems a new joist is laid beside the old one and fastened to it.

How to sister a roof joist.

How much repairing floor joists should cost. For open ceilings set scaffolding to sister a roof rafter. However doing this does not fix the slant that the floor has taken since the old joists got damaged. When the sagging joists are level apply a generous bead of construction adhesive to the existing joist.

Consider how weakened or damaged the joists are and also whether a weight above them could be causing the joists to fail. 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. Framing lumber is the typical. Predrill and drive 3 8 in.

I joists would have been a good bet. No sistering or modification of i joists to the existing situation he says. In his own garage he used i joists with 2 4 flanges for a 30 ft. Calvin suggests that i joists would have been an alternative to consider at the start of the project.

Average costs and comments from costhelper s team of professional journalists and community of users. Step 1 evaluate your situation. Sistering joists means beefing them up with additional material. How to sister a floor joist.

In attics it s best to place strips of plywood across the ceiling joist as a work platform. Then attach the sister joist using three 16d common nails driven every 16 in. Driving 16d common nails in old hard wood is difficult. Take some extra time and jack the damaged area up so that the new lumber doesn t need to be notched.

Rather than reinstall your joists you can create second or sister joists alongside the first. Lag screws if you re having trouble nailing.