How to Cut Holes in Floors for Ducting

When you need to run ductwork from the basement up to the first floor, or from the first floor to a higher floor, you must cut holes in the subfloor and sill plate -- the horizontal board on the floor, underneath the wall studs. These holes should be placed between two wall studs, so the duct can be hidden behind the finished wall. The hole's side will be based on the type of duct being run through the hole. Cut the hole just large enough for it to fit through.

Tape measure
1/4-inch drill bit
Drill
Circular saw

Instructions

- 1
  Measure the duct's length and width. Transfer these measurements onto the subfloor and sill plate, forming a rectangle. If the hole will lead to a heat register, plan to make the hole on the subfloor -- about 3 inches in front of the sill plate.
- 2
  Drill a 1/4-inch pilot hole through the subfloor and sill plate, in the center of the rectangle. Go to the level below the subfloor -- either the basement or a lower level of your home -- and locate the pilot hole. Check that the hole you plan to cut will not interfere with any of the lower level's ceiling joists. Adjust the hole if necessary.
- 3
  Set a circular saw to the appropriate depth to cut through the subfloor and sill plate. Follow the tracing you made in Step 1 with the saw's blade to cut the hole in the floor.

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