How to Reinforce a Floor for a Waterbed

Remove any carpeting or floorboards and underlayment from the area of the floor that you need to reinforce for the waterbed placement. Pull the edge of any carpeting from the tack strip running along the floor edge against the wall and then roll the carpet out of the way, along with the carpet padding. Remove floorboards by prying them from the floor’s surface with a pry bar at nailed locations. Or, you can loosen any glue holding them in place with about 30 seconds of heat directed at the surface of the boards with a heat gun before prying the boards up. Set the boards aside for later replacement.

Remove the subfloor panels over the reinforcement area by prying them up from the floor at the panel edges with the pry bar. Concentrate the pry bar use at the nailed location of the panels to avoid breaking them as you pry them upward. Set the panels aside so you can place them back onto the floor after reinforcement.

Measure the size of the planks used for the exposed floor joists in the floor. Use the same size planks to create the blocking boards needed for reinforcement.

Measure the distance between joists before cutting and placing each blocking board to ensure that you won’t throw off the joist spacing with the blocking installation. Snap a chalk line running perpendicular over the floor joists every 8 feet.

Cut the blocking boards with a circular saw to fit between the joists. Slide the blocks between the joists so that the blocks are flush with the surface of the floor joists, and stand on the same end of the joist so that the block extends down to the joist base. Position the block to one side of the chalk line, and then nail the board in place using 16d nails and a hammer. Place at least two nails per block end. Position all of the blocks in the same joist space row on the same side of the chalk lines.

Fill the next joist space with blocks placed on the other side of the chalk lines so that the blocking boards are staggered. Nail them into place and continue placing the boards throughout the area uncovered by the panel removal, reinforcing the entire floor space beneath where you intend to place the waterbed.

Check the level of the block with the level of the two joists with a carpenter’s level. Trim the blocks to level them with a hand planer, if necessary.

Return the panels to the floor, nailing them back into place, and then restore the floor covering material.