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Build a platform with drop-in bathtub

  • Difficulty: hammer hammer hammer
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    Beginner Do-It-Yourselfer - Easy
    Intermediate Do-It-Yourselfer - Moderate
    Experienced Do-It-Yourselfer - Difficult
    Professional - Expert

A bathtub built into a custom-made platform will add class and luxury to your bathroom. Placed in the corner of the room, along a wall or even as a centre island, it’s perfect for those who like to take a long soak!
The following project provides all the instructions you need to design and build the platform surround, to insert the tub, and to connect up the plumbing and faucets. This is nevertheless a challenging project, which requires a certain amount of experience in carpentry and plumbing. You will need someone to help you handle the bathtub as it is heavy and cumbersome.

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Tools and materials required

TOOLS

  • Table saw
  • Adjustable wrench
  • Pipe wrench
  • Pipe cutter
  • Pencil
  • Drywall knife
  • Square
  • 3/16 bit
  • Spirit level
  • Power drill
  • Pliers
  • Plier wrench
  • Measuring tape
  • Circular saw
  • Hole saw
  • Hacksaw
  • Jigsaw
  • Screwdriver

MATERIALS

  • Bathtub
  • Template
  • Faucet
  • 10 lengths of 2" × 3" × 96" (or 2" × 4" or 2" × 6")
  • 2 sheets of plywood (or more depending on platform size and number of visible sides)
  • Wood blocks - 2" × 2" × 3"
  • Wood shims
  • Silicone caulk
  • Rags
  • Glue for ABS pipes
  • Bath-drain connection set with appropriate ABS pipes
  • Mortar
  • Caulking gun
  • PEX (cross-linked polyethylene) tubing with appropriate couplings and connectors
  • 2 ½" and 1 ½" no. 8 screws

Before Assembly

This project does not cover related topics on how to enlarge the surface of a bathtub platform, build a toe-kick, build an alcove bathtub platform or design a bathtub platform with a step.

BEFORE YOU START

Check that the floor is level and solid. It must be strong enough to support 50 lbs/ft² (245 kg/m²).
Read the bathtub specifications before building the platform.
Keep the template printed on the tub’s packaging as a guide to cut the plywood for the top of the platform.
If remodelling an existing bathroom, remove the wall covering in the areas that will be covered by the new platform (if applicable).

HANDLING THE BATHTUB

Choose a bathtub that will fit easily through your bathroom doorway.
After removing the packaging, inspect the tub thoroughly to ensure it is in perfect condition (no nicks or scratches).
Leave the plastic film in place around the tub to protect it during installation. Lay some pieces of cardboard (without any staples or metal fasteners) in the bottom of the tub to protect it.
If creating a brand new bathroom, take the bathtub into the room before building the walls.

PLATFORM STRUCTURE

The rim of the platform on the side where you enter the bath should be no more than 3" – 4" wide. If it is any wider it may be difficult for children or elderly people to step in and out of the bath, for parents to wash young children in the bath, or to reach the inside of the tub for cleaning.
The base of the tub must rest on the floor; the tub must never be supported solely by its rim.
For whirlpool or therapeutic tubs, space must be left in the framework for a panel measuring at least 30" × 15" to allow access to the pipes and system. For regular tubs an access panel is not absolutely necessary but it is recommended as it allows quick and easy access to the plumbing if needed. Some manufacturers also require an aeration hatch.
Check that your installation complies with the applicable building codes in your area.

LEVELLING THE BATHTUB

Some bathtubs come with an integral pre-levelled support frame. If your floor is level, no adjustments will be necessary. As long as the tub is level, the water will drain properly.
The rims of the tub must be level. The tub must be level both lengthwise and widthwise. Check using the spirit level.
Wood shims are generally used to level standard bathtubs, whether or not the tub has a support frame. Tubs without a support frame can also be levelled with a mortar bed.

PRELIMINARY PLUMBING

Remodelling project without moving existing pipework:
Choose a bathtub with a waste pipe that is positioned for easy connection to the existing plumbing. Measure carefully, as the waste pipes from the tub must fit into the floor drain.
To connect the water supply lines, PEX (cross-linked polyethylene) tubing is flexible and easy to work with, but first check that you will be able to run the piping to the planned faucet location.
New installation:
If there is no existing pipework, you can plan the position of the floor drain according to your chosen type of bathtub. Be sure to measure accurately!
The drain hole in the floor should be approximately 6” wide x 12” long so as to insert the ABS waste pipes from the bathtub. Before cutting the hole, check there are no joists, wires or other pipes running under the floor in that location.
For this project, we are assuming that the water supply lines and floor drain are already installed. Block the floor drain opening with a rag to keep debris out.

FAUCETS

Position the faucets so they are easy to reach from outside the bathtub (e.g. for running a child’s bath) and especially so they do not get in the way when entering the tub.
A faucet with shower attachment is a must for cleaning and rinsing the tub.
Use the recommended size of pipes for the bathtub faucets (½" interior diameter). These pipes are wider than those used with washbasin faucets and therefore provide a higher flow rate.
Ensure the bathtub has a wide-enough rim to accommodate the faucets. If the faucets are on the platform casing rather than the tub, make sure the spout is long enough to reach over the tub.

ELECTRICITY

If you are fitting lighting around the platform edge or installing a whirlpool or therapeutic tub, you will need electricity. All electrical connections must be made by a qualified electrician to ensure safety. Protect the circuit with a ground-fault circuit interrupter receptacle.
Have the plumbing and electrical (if applicable) work done by qualified professionals.

Steps

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Helpful Information

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Build a platform with drop-in bathtub