Maine tile contractor Tom Boucher shows how to quickly install a watertight recessed shelf opening for a tile shower using a pre-made box from Schluter Systems.
The frame of the pre-built box measures exactly two inches. Boucher will account for this as he positions the box to match his wall tile layout.
Boucher marks the shower wall for his cut. He'll install the recess box so that a full tile will fall flush with the lower edge of the box.
Boucher lays a laser guideline onto the wall to mark the spot for his box cut-out on the existing Kerdi-Board.
Bouchet probes with a razor knife to locate the edge of the wall stud behind the Kerdi-Board.
Guided by the laser layout lines, Boucher holds the pre-built recess box face to the shower wall and marks its outline for the cuts.
Boucher removes the previously-installed Kerdi membrane over a fastener that falls at the place where the new box must be positioned.
Using his knife, Boucher digs away the mortar covering the existing screw and washer that holds the Kerdi-Board to the wall stud.
Boucher cuts a small triangular opening into the face of the wall where the box opening must be placed, to give himself a handhold on the piece of Kerdi-Board to be removed.
The wall between the shower and the adjoining bedroom has been soundproofed with rock wool insulation, which needs to come out.
Boucher places the box in the opening temporarily. He still has to cut out the opening for another box right next to this one.
Boucher lays another recess box onto the wall next to the first one, and traces its outline onto the wall. He will now repeat the step of cutting out the opening.
Boucher removes the section of Kerdi-Board from the location where the second box will be installed.
This box installation is complicated by the presence of a bedside lighting receptacle for the next-door bedroom, which can't be relocated. Fortunately, the 2x6 wall framing allows enough depth to hold both the recess box and the wiring box.
To make room for his shower recess box, Boucher has to chisel away a piece of the scabbed-on 2x4 that the electricians used to attach their wiring box.
Because the space is quite tight, Boucher has to carefully trim away the edges of the block with a Fein Multimaster.
To preserve at least some of the soundproofing effect, Boucher replaces two inches of rock wool in the cavity.
Boucher sets fastener washers into the seams where the recess boxes meet over the wall studs.
Boucher screws the washers down onto the Kerdi-Board to fasten the box firmly to the framing.
Boucher cuts a square of Kerdi membrane from a 100-foot by 1-meter roll of the material. He will apply this piece over the entire assembly of two recess boxes, then cut out for the box face openings.
Boucher works unmodified cement mortar into the flocked face of the Kerdi-Board boxes and the surrounding wall.
Using a Kerdi trowel with quarter-inch teeth, Boucher applies a measured amount of mortar to the wall where the membrane will be set.
Boucher lays his pre-cut piece of Kerdi membrane over the two boxes, completely covering the mortared joints.
Boucher uses a six-inch drywall knife with the corners ground down to press the membrane into the mortar. He can see well enough through the membrane to visually check that the quarter-inch grooves in the mortar have been fully smoothed down, indicating a full mortar bond with the membrane.
Boucher cuts out the openings with his knife (a task that is easiest before the mortar has set).