Improper Repair Of Floor Joists

Improper notching can weaken a floor joist.

Improper repair of floor joists.

Improper holes and notches from alterations and running service lines are a major source of weakened joists. Generally there should never be any cuts or penetrations in the middle third of any joist or anywhere along the bottom of the joist. 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. Use common sense when deciding how many fasteners to use.

Tack a beam under the sagging joists. Click the image to enlarge. Splicing with plywood can have some advantages over splicing with a solid joist in many situations. Pictured is joist repair method for end rotted joist using plywood and some suggestions for best practice.

However doing this does not fix the slant that the floor has taken since the old joists got damaged. Set a hydraulic jack and post under the beam and jack up the joists about 1 8 in. A day until they re level. Floor is sinking between the floor joists.

This will not work as the joist was not designed for this load originally. Finally if all else fails drop your pipes and ducts down below the joists and box them in with wood framed soffits. The notch was made where the floor joist recessed into a wood beam supported by chimney corbeling. A common but improper repair by other contractors is to install more full length joists.

Position bathroom vent fans so the ducts can run parallel to the joists right up to where they exit the house. Nailing two 2x4s together will work to span about three joists unless the sag is under a weight bearing wall. Repairing flooring vinyl wood or tile costs 347 on average or between 188 and 512 because pros need to go through this layer to get to the structural elements of subfloors and joists expect to pay far more for structural repairs. 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.

Make sure not to install joists so they run parallel to and directly under walls where you intend to install ductwork. Take some extra time and jack the damaged area up so that the new lumber doesn t need to be notched.