Call in a structural engineer.
How to sister roof joists.
Take some extra time and jack the damaged area up so that the new lumber doesn t need to be.
How to sister a roof rafter 1.
Fasten the sister joist to the existing joist with three nails every 16 in.
Nail 10d or 16d common nails through the sister and into the existing joist.
Run the rows parallel and an inch.
How to make structural repairs by sistering floor joists sistering floor joists.
Nail the new joist in place.
The longer the overlap distance the stronger the connection.
In these cases the overlapped joists help tie the framing together by combining the rigid members over a beam.
However doing this does not fix the slant that the floor has taken since the old joists got damaged.
Sistering joists is commonly used when adding onto an existing deck or repairing a deck.
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.
Measure the overall distance of the existing rafter from the ridge board to the outermost point where the rafter.
Make two rows of nails spaced 16 inches or less apart along the length of the sister.