Bathroom waterproofing: where it's needed and how to check it

Where waterproofing is needed

In the app's route, the item reads: coat the screed and the walls of bathrooms and the kitchen with liquid waterproofing, with tape in the corners and collars on the outlets and drain. Its hint gives a guide for height:

• on bathroom walls - at least 20 cm up from the floor;
• in the shower - the full height of the wall that gets wet.

Pay special attention to the spots where water finds its way fastest:

• corners between the floor and walls and between walls - tape goes there;
• pipe outlets from the floor and walls - they get collars;
• the shower drain or channel - its body is installed before the screed, and when waterproofing it gets a collar.

The “Waterproofing” stage in the route is currently under review by a builder, and its items may change. The make-up and thickness of the layer for your material come from its manufacturer, and for your flat - from the design.

When it's done

The order in the app's route is:

1. Floor preparation and screed. Before pouring, the drain or channel body is installed and its height set for the screed fall: after the screed the drain can't be moved. Everything that goes into the screed is photographed.
2. The screed dries. Before waterproofing, measure the screed moisture and write down the reading. The route's guide: a semi-dry screed dries 3-7 days before waterproofing, a wet one from 14. Drying isn't sped up with heaters.
3. Waterproofing, photos and the flood test.
4. Stage acceptance - before tiling starts.
5. Tiling. The tiler's first item is to check that the waterproofing is done and has dried.

More about the screed is in Floor screed: when to pour and how to check.

How to check waterproofing

Inspection

While there are no tiles, the waterproofing is visible. Look at:

• whether the whole floor of the wet area is covered, with no gaps;
• whether the layer goes up the walls and how high - measure with a tape;
• whether there's tape in every corner and at the floor-wall joint;
• whether there are collars on every pipe outlet and on the drain.

Photos

Photograph the tapes, collars, drain and the waterproofing height on the walls with a tape measure in the shot. Take each wall in full and the joints close up, and label the room. After tiling the waterproofing can't be seen - the photo remains the proof. The app has the “Photograph the waterproofing” item for this.

Flood test

Flood the bathroom floor with 1-2 cm of water and leave it for a day. Then check the ceiling of the neighbours below - agree with them in advance. The test is done before tiling: a leak to the neighbours is the costliest renovation mistake.

If the water level has dropped or a stain has appeared at the neighbours', don't accept the stage: let the contractor find the spot and fix it, then repeat the flood test.

How to accept the stage in the app

1. The contractor checks off the items, attaches photos and taps “Send for review”.
2. You or the designer open the stage and look at the photos and the flood test result.
3. All good - “Accept work”. Something's wrong - “I have remarks”: write what needs fixing.

Only after the stage is accepted is it worth letting the tiler in. How to review work stage by stage is in How to accept work from the crew stage by stage.

Common mistakes

The hints in the app's route warn about these mistakes:

• treating tiles as waterproofing - they aren't, and the waterproofing has to be accepted before tiling;
• not setting the drain before the screed - the screed makes the fall to the drain, and after it the drain can't be moved;
• speeding up screed drying with heaters - don't; wait and measure the moisture;
• not photographing the waterproofing - after tiling it can't be seen, and there'll be nothing to prove it's there.

What else protects against leaks

• The bathtub or shower tray goes in before the wall tiles: the tiles are taken over the bathtub rim, and the joint is sealed on top.
• Fixtures at the final installation - after installing, every connection is checked for leaks.
• The glass shower screen is tested with the shower: water mustn't get past the tray or drain.
• A leak protection system, if you planned one: valves and sensors go in with the plumbing, and at the final installation they're tested by actually wetting a sensor.

How to check the pipes before the boxing is closed is in Plumbing: pressure test and checks.

If a wet area is moved

Moving a bathroom or kitchen is a re-equipment, and it has its own rules, including where wet areas may be placed relative to the neighbours. Before moving the drain and outlets, read Alterations: what you can do without approval.

Checklist before tiling

• The screed has dried, and its moisture is measured and written down.
• The floor of wet areas is fully covered, walls at least 20 cm up, the shower full height.
• Tape in every corner, collars on every outlet and on the drain.
• There are photos of every wall and joint with a tape measure in the shot.
• The flood test has stood for a day, and it's dry at the neighbours' below.
• The “Waterproofing” stage is accepted in the app.