Improper Repair Of Floor Joists

Improper notching can weaken a floor joist.

Improper repair of floor joists.

Floor is sinking between the floor joists. However doing this does not fix the slant that the floor has taken since the old joists got damaged. Improper holes and notches from alterations and running service lines are a major source of weakened joists. A day until they re level.

Tack a beam under the sagging joists. Pictured is joist repair method for end rotted joist using plywood and some suggestions for best practice. Position bathroom vent fans so the ducts can run parallel to the joists right up to where they exit the house. Generally there should never be any cuts or penetrations in the middle third of any joist or anywhere along the bottom of the joist.

Splicing with plywood can have some advantages over splicing with a solid joist in many situations. Finally if all else fails drop your pipes and ducts down below the joists and box them in with wood framed soffits. Notches at the end of a joist should not exceed 1 4 of the joist depth. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall.

Jacking them up too fast may cause cracks in the walls and floors overhead. Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. This will not work as the joist was not designed for this load originally. The notch was made where the floor joist recessed into a wood beam supported by chimney corbeling.

Corbeling is an old school overlapping arrangement of bricks with each course extending farther out from the vertical of the wall than the course below. Make sure not to install joists so they run parallel to and directly under walls where you intend to install ductwork. 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. Total costs will depend on the extent of the damage and the ease of access to the joists through a basement or crawlspace but in general sistering averages 100 300 or more per joist and could run 1 000 3 000 or more to repair a tilted wavy or bouncy floor under an average room.

A common but improper repair by other contractors is to install more full length joists. Use common sense when deciding how many fasteners to use.