Before Installing Your Tub & Hydroblok™ Wallboard

Ensure all plumbing and wall studs are in their required locations before beginning installation. Check that the floor and wall studs are secure, and add additional blocking if needed. Your tub manufacturer’s instructions will show recommended stud placement.

If your tub does not include a pre-molded flange, install a waterproof tub flange for tile as specified by the manufacturer and local building codes. Make sure the tub is securely fastened as per manufacturer directions.

Note: ½” and ⅝” Hydroblok™ Wallboard must be installed with a maximum stud spacing of 16” on-center. When fastening the tub to the wall studs, ensure screws attaching the tub flange are countersunk and flush with the flange.

Installation Tools & Materials Required

• ½” to ⅝” Hydroblok™ Wallboard

• Hydroblok™ Washers and Screws

• Hydroblok™ Joint Sealant (use HYDROBLOK Sausage Gun or Skeleton Gun)

• Putty knives (flat and corner blades)

• Cordless or electric drill with #2 Robertson or #2 Phillips bit

• Tape measure and marker/pencil

• Sharp utility or razor knife with a metal straight edge

• Cleaning supplies (paper towels, citrus wipes, rags, dustpan, brush)

Important: Read all related installation guides before starting. Contact your local dealer if you have questions about the installation process.

Installing Hydroblok™ Wallboard Around the Tub

Hydroblok™ Wallboard should first be installed on the back wall of the tub enclosure, followed by the side walls.

1. Measure and cut the required wallboard pieces.

   • For vertical cuts, measure from the tub deck to the top of the wall, subtracting ⅛” for the gap between the wallboard and tub deck.

2. If the tub flange is deeper than ⅛”, cut a notch into the wallboard to fit flush against the studs.

   • Measure the flange height and depth, and use a sharp utility knife with a straight edge to cut a clean notch.

   • The wallboard should sit plumb against the studs and square in the corners.

   • Dry-fit all pieces before applying sealant.

3. Apply sealant:

   • Run two continuous ¼” beads of Hydroblok™ Joint Sealant along the back side of the tub flange.

   • Apply one continuous ⅜” bead on the tub deck next to the flange.

4. Press the lower edge of each wallboard panel into the bead on the tub deck, then against the back wall and sealant on the flange.

   • Secure with screws and washers every 12” up each stud.

   • Do not install the uppermost screws until all rear panels are in place.

Installing Multiple Boards

If multiple boards are needed:

1. Apply a ½” continuous bead of Hydroblok™ Joint Sealant along the edge of the previously installed wallboard (for horizontal and vertical seams).

2. Gently lower the next board into place, pressing it into the bead of sealant.

3. Secure with screws and washers starting 12” above the seam, then add fasteners along the studs at the joint.

4. Use a Hydroblok™ putty knife to smooth excess sealant across seams, covering screws and washers fully.

Installing Side Wallboards

1. Measure and mark all plumbing fixture locations carefully.

2. Cut required openings with a utility knife before installation.

3. Apply a ½” continuous bead of Joint Sealant on the rear wallboard edge where the side panel will meet.

4. When positioning the side panels, press them firmly into the joint sealant on the rear wallboard, tub, and flange.

5. Secure with screws and washers at all stud locations.

6. Use a Hydroblok™ corner putty knife to smooth excess sealant in corners where the side and rear panels meet.

Finishing & Sealing

1. Apply ½” dabs of Hydroblok™ Joint Sealant on all washers, smoothing with a putty knife to fully cover them.

2. Apply a continuous ½” bead of sealant along all seams and smooth again with a corner knife so seams are fully covered.

   • Ensure at least 1” of sealant coverage on either side of every seam.

3. Clean any excess sealant from the tub surface with mineral spirits or citrus wipes.

After about one hour (at ≥18°C / 65°F), the Joint Sealant will skin over, and thinset can be safely applied.