Fine Homebuilding Project Guides

Tiling

How-To

Expansion Joints in Tile Floors

Caulk expansion joints between sections of a tile floor to allow it to expand and contract.

To allow a tile floor to expand and contract and prevent the problems movement can cause, you must add expansion joints between sections of tile. Expansion joints are spaces filled with flexible caulk that allows movement. On large floors, tile industry standards call for an expansion joint every 24 ft. to 36 ft.

On floors that are smaller than this, it’s adequate to leave a space wherever the floor meets a wall, column, or other obstacle. This expansion joint is no less than 1/4 in. to 1/2 in. wide, and must be figured in when laying out and setting the tile.

Before caulking expansion joints, you must protect adjacent tiles by covering them with kraft paper taped in place 1. Vacuum out any debris so that all joints are clean 2. If expansion joints are 1/2 in. deep or more, install a strip of flexible foam material to reduce the amount of caulking you need to apply.

Push the strip down into all the joints around the floor, using a margin trowel or other tool to make sure it seats firmly and doesn’t stick up above the tile surface 3. Apply the caulk into the joint over the foam, making sure it fills up to the top of the tile 4. On wide joints, you may have to apply the bead in two passes. Often, the joint will be covered by baseboard when the floor is completed. But if the joint will show, use a moistened finger to smooth the caulk and touch up as necessary 5. As soon as you are finished caulking along one wall, pull up the tape and paper before the caulk has a chance to dry and stick to the tape 6.

	1. Before caulking a floor, use blue tape and paper to protect the perimeter.
	2. Vacuum out any debris from the joint before caulking.
	3. Push flexible foam backing into the joint with the end of a margin trowel.
	4. Caulk the joint, making sure that it is filled.
	5. Smooth the joint with a dampened finger and touch up if necessary.
	6. Remove the tape and paper before the caulk dries.