How to Remove Subfloor Joists

Lift the flooring surface to gain access to the floor joists from above. If you have a wood floor, this will involve prying up the floor covering with a crowbar. Tile floors will have to be broken up with a chisel and removed. Laminate, linoleum or stick-on flooring can be lifted with a putty knife and hammer to separate the floor from its glue. Pull up carpeted floors around the edges first then detach them from the tack-less strips that hold them in place.

Raise a section of your subfloor to gain access to the joists below. Subflooring is typically applied in sheets, which may be up to 4-by-8 feet in size. Locate an edge of the subfloor and use a crowbar to work into the seam. Pry the sheet upward on all sides then lift it out of place. If you have access to the underside of your floor from the story below, use a hammer to strike along the seam of the subfloor to raise the edge. Then use the crowbar to remove it from above.

Add some extra support to the area of subfloor you plan to remove. Install a full length of 2-by-4 lumber alongside the uncut joists that flank the one(s) you plan on cutting. Use your hammer and nails to fasten the 2-by-4s in place so that their midpoints line up with the cutting location.

Locate the damaged portion of the subfloor joists. Extend a circular saw blade to the thickness of the joist and cut on either side of the damaged portion. Remove the bad joist and discard it. Use a reciprocating power saw to make the cut if the circular saw blade is not deep enough.

Install two pieces of 2-by-4 lumber between the joists that flank the one(s) you just cut along the joists' exposed ends. Measure the gap between the two joists then use the circular saw to cut the wood to fit for cross supports. Place each support in place so it is flush with the top edge of the existing joist then use a screw gun and wood screws to mount it in place at both ends with steel joist hanger brackets. Repeat the same process across the other exposed joist ends.

Fasten the exposed ends of the cut joists to the cross supports with the screw gun, wood screws and steel joist hanger brackets. The weight and pressure of the opening you created is now being channeled around the weak point so the floor remains strong. Reinstall the subflooring and floor covering.