Measurement

• The first thing you need to do when building a whirlpool base is to measure the whirlpool itself and the space in which you intend to install it. You need to determine the width and the length of the tub and also determine the amount of space you want the base for the tub to stick out from the whirlpool. You also need to determine the height of the deck by measuring how far the whirlpool will sit above your subfloor.
  
  

Framing

• Once you've made your measurements, you need to cut the wood for the frame and begin to put it in place. Most of the wood you will use for this project will be 2-by-4's and plywood. Buy pressure-treated wood to ensure maximum durability. If building into an existing space with surrounding walls, attach the frame to the walls and subfloor. Otherwise, you will need to build the base as a freestanding unit with four full sides. Cut a hole in the plywood that the whirlpool will be able to sit in. Attach the plywood to the top of the frame. Cut and attach plywood sides for the base as well.
  
  

Waterproofing

• Once you've built the wooden portion of the frame, you need to waterproof it by applying mortar to the plywood and allowing it to dry. You also need to apply a waterproof membrane to the mortar to keep it from leaking. You must also apply caulk around the walls where the frame attaches to the cabinet. You can skip the mortaring step if you only plan on building the wooden frame for an outdoor structure. You will need to add some type of water seal to the wood if you plan to go this route.
  
  

Add the Tub

• Once the cabinet structure is in place, the remaining step is simply a matter of dropping the whirlpool tub into the frame and securing it in place. The whirlpool should sit in the cabinet snugly enough to form a tight bond with the cabinet. Your final step will involve caulking around the rim of the tub where it contacts the frame.