How To Build A Wet Room On A Concrete Floor

Building a wet room on a concrete floor is an easy DIY project and can be completed in a weekend. Here we show you how to build it, starting with the materials you’ll need, including cement boards and waterproofing membranes. You can then finish the surface with whatever waterproof flooring material suits your taste – like tile, mosaic or even paint.

A wet room is a totally waterproof room that you can use as an extension to your bathroom, or as a shower cubicle in its own right. To build a wet room on a concrete floor you will need to create a completely waterproof boundary around the room, seal the walls and ceiling, then fit your chosen showering and lighting fixtures. Steps 1. Lay 1/2 inch polystyrene insulation along the back wall of your wet room. 2. Lay polystyrene melted edges over the walls surfaces so the polystyrene protrudes about 1/4 inch onto all sides to allow water to run off when it falls off the wall down into the grout channels between the tiles. 3. Apply half inch ready rolled jointing compound to the walls, feathering out at 45° using a rag around the edge of where each sheet of tiles will sit. 4. Lay tile squares over the wall surface starting from top left corner working your way up and down toward bottom right corner 5

A wet room is an up-to-date take on a traditional bathroom. It is designed to drain water away through the floor and has no separate shower tray or screen. This makes it ideal for small bathrooms, where the lack of barriers means that there’s more floor space on show. You can create a wet room on any type of floor construction, but if you have a concrete floor, then there are some extra issues to consider. Before getting started, don’t forget that your finished wet room needs to be tiled from floor to ceiling with wall tiles at least 8 inches high. Also bear in mind that you must use special waterproofing materials when installing a wet room because the entire area will be exposed to water.


  • Prepare the floor.
  • Prepare the walls.
  • Prepare the ceiling.
  • Prepare the floor surface.
  • Prepare the floor drains.
  • Install your choice of flooring over them all.

Install the wet room floor formers.

Install the wet room floor formers.

  • Cover the concrete floor with plastic sheeting, ensuring that there is enough overhang to cover any expansion joints.
  • Place the wet room floor formers over the plastic sheeting, overlapping where necessary.
  • Insert screws through each corner of each frame and into the subfloor below, using your cordless drill or screwdriver.

Fix the trap and waste pipe.

To fit the trap, remove the old one and use a hacksaw to cut about 10mm off the bottom of it. This will allow enough space for you to slide in the new trap. There should be a rubber seal around the edge, so make sure that this is pushed all around when fitting it. Be careful not to damage any part of your floor surface with the saw blade or screws when removing or fitting them in place: they can leave dents that are very difficult to get rid of! Now fit your waste pipe – this should simply push into place, but if you find yours doesn’t fit easily then try using some WD40 on all threads first. Then seal any gaps between it and both floors and walls with silicone caulk or mastic; apply generously by smearing onto both surfaces and then pressing them together until they meet cleanly without leaving any gaps between each other.

Install the insulation board.

Insulation boards are required to meet minimum thermal performance standards. It must be laid over the screed and covered with a layer of screed at least 150mm (6 inches) thick.

Install screed.

  • Check the surface for level with a spirit level and then use a trowel to apply the screed.
  • Make sure that the thickness of the screed is not too thick, as it will be more difficult to get a good finish later on. If you don’t have access to a trowel (perhaps because you are doing this project as part of an event or competition), you can use a piece of wood instead; just make sure it’s flat and smooth before applying any mortar or render to it.


  • Waterproofing.

The waterproofing membrane is the most important component of any wet room. This will keep moisture from seeping through your floor and walls and is an absolute must when it comes to creating a safe and durable space for you to enjoy for years to come. The good news is that this part doesn’t have to be difficult, as we’ve got some simple tips on how to do it right:

  • Apply a layer of waterproofing membrane over the entire floor area before laying down any other materials. This will prevent any water from seeping between layers and causing damage later on down the line.
  • Apply another layer of waterproofing membrane onto all sides (walls, ceiling) of your room’s walls so that everything stays nice and dry even if there are leaks or excessive humidity in places like bathrooms or kitchens nearby where this could happen more frequently than expected due to regular use by others living there too.

Final touches.

  • Install the shower tray.
  • Install the shower door and frame.
  • Install the shower head.
  • Install the shower curtain.
  • Install the shower handles, spout, and flanges (if applicable).
  • Place a soap dish in your desired location and secure it with screws or adhesive glue (if applicable). If you have a towel bar, place it on one side of your wet room if possible or install two towel bars if needed. Attach hooks to support your hand towel(s) near your toilet or vanity area so that you won’t have to walk into a puddle every time you want to dry off after taking a leak. Screw down any loose tiles with tile caulk to prevent them from shifting during use. Place railings against walls if needed for balance or safety reasons

Learn how to build a wet room on a concrete floor in this step-by-step guide with photos and videos.

  • Learn how to build a wet room on a concrete floor in this step-by-step guide with photos and videos.
  • Find out how to build a wet room on a concrete floor by following these simple steps.

Final words

The process for installing a wet room on a concrete floor is quite similar to the one above. In fact, it’s even simpler because you don’t need to do any of the wooden frame construction. Since your first job is to waterproof the concrete floor, we recommend starting with that step and then build up from there. Once you’ve got a good handle on how to waterproof your bathroom, you can go ahead and install everything else according to our other guide.

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