DIY Network

How to Install a Shower Sub-Floor and Shower Base

DIY Network expert and licensed contractor Amy Matthews shows how to install a plywood shower sub-floor and shower base.

More in Bathroom

  • Time


  • Price Range

    $500 - $1,000

  • Difficulty



Step 1: Install the Shower Sub-Floor

As part of a bathroom renovation, we install a shower sub-floor and shower base. Shower bases are important to install correctly as they allow water to drain away into the plumbing.

Begin by making a level sub-floor. Use a 1/2" spade bit to drill a starter hole in the plywood for the drain. Use a saber saw to cut a hole in the board to accommodate the drain (Image 1).

Line up the cut out hole with the drain pipe and place it on the floor (Image 2).

Measure the location of the joist and mark them on the plywood so you know where to put the screws.

Screw in 2-1/4" hex screws where you've placed the marks

Step 2: Install the Shower Base

Line up the drainpipe and drain hole on the shower base and carefully set the base down in place to dry fit. The drain hole should fit securely into the pipe in the center of the base.

Remove the base and cut the PVC drainpipe flush with the new sub-floor using a hand saw.

Cut and insert 2" x 4" wood blocks between the studs near the floor and toenail them into the studs.

Install 1" x 2" cleats 4" off the floor to support the shower base flange.

Screw the drain assembly to the shower base (Image 1).

Before putting the shower base in place, "sweat" the water supply pigtail to the shower base pipe and then slide the shower base into place. For copper piping, sweat in place by soldering using a blow torch after using a pipe cleaner or wire brush on all connecting areas and applying flux to the prepared connection areas. Use hand soap to lubricate the gasket and slide into the drain. Screw the caulking nut using a spanning wrench. Next screw on the strainer.

Cover the base of the shower with a drop cloth to protect it from scratches.

Using 1-1/2" screws, screw the retaining brackets (Image 2) to previously installed backer boards on the shower wall to hold the base in place.