Building or redoing a bathroom? Get the waterproofing right before the tiles go on
Once the tiles are on, nobody can see the waterproofing again, so most bathroom leaks in new homes come from work that was skipped or rushed at this stage. If you are building or fully redoing a bathroom, these are the steps to see with your own eyes before tiling starts.
Published
Plan my waterproofingPart of the bathroom leakage guide, which covers every usual source.
Use this guide when
- The bathroom floor and walls are open down to concrete or brick
- Pipes and the floor drain are being fixed
- A sunken floor is being filled
- The tiler is ready to start
What a proper bathroom waterproofing includes
Check each stage on site before the next one covers it.
Stage 1
A clean, sound base
Waterproofing only bonds to a clean, solid surface.
What to check on site: Loose mortar, dust and oil are removed; cracks are filled.
What good work looks like: The concrete or plaster is cleaned back to a sound surface and slightly damp, not wet, before the first coat.
Stage 2
Corners and pipes treated first
Wall-floor corners and pipes through the floor are where most bathroom leaks start.
What to check on site: Every corner has a strip or fillet, and every pipe through the floor has a collar.
What good work looks like: Corner tape or a rounded mortar fillet along all wall-floor joints, and pipe collars bonded into the waterproof layer.
Stage 3
A flexible waterproof coat on floor and walls
The layer that actually keeps water in the bathroom.
What to check on site: At least two coats, the second at right angles to the first, carried up the walls, higher in the shower.
What good work looks like: A flexible cementitious or liquid membrane to the thickness the system specifies, taken up the walls about 300 mm and to full height in the shower area.
Stage 4
Slope to the drain
Water that stands on the floor eventually finds a way through.
What to check on site: Pour water on the screed before tiling and watch it run to the drain.
What good work looks like: The screed or fill is formed to fall towards the drain, with the drain body sealed into the waterproof layer.
Stage 5
A pond test before tiles
The only proof the waterproofing works before it is hidden.
What to check on site: Block the drain, fill 2 to 3 cm of water and leave it at least 24 hours; check below and beside.
What good work looks like: No damp below or beside after the test. Only then does tiling start.
Stage 6
Epoxy grout in the joints
Cement grout is porous and lets water reach the layer below every day.
What to check on site: Ask what grout the tiler will use before tiling starts.
What good work looks like: Epoxy grout in floor joints and wet-zone wall joints.
Methods follow proven, manufacturer-approved waterproofing systems. The right one for your building depends on what is found on site.
What a photo can and cannot tell you
Photo guidance points to the likely source. It is not a confirmed diagnosis.
A clear photo can show
- Whether corners and pipes have been treated
- Coverage of the waterproof coat on floor and walls
- Slope towards the drain, with water on the floor
A photo cannot settle
- The thickness of the coating
- Whether the coat has bonded properly to the base
Simple checks before you call anyone
- 1Visit the site at the corner-treatment stage and the coating stage, not only at the end.
- 2Take photos of every stage before it is covered.
- 3Insist on the pond test and be there to see it.
- 4Check the slope with a bucket of water before tiles go on.
When you need someone on site
- You cannot be on site at each stage yourself
- The bathroom is above a living room or bedroom
- The contractor wants to tile without a pond test
Where Membrain works on site, a site diagnosis confirms the source, and thermal imaging finds hidden leaks before anything is broken. The app checks whether your pincode is covered.
Common mistakes that waste money
- Tiling without a pond test.
- Coating only the floor and not the walls.
- Skipping pipe collars and corner treatment.
- Using cement grout in the shower area.
Before you accept a contractor's quote
- Does the quote name the waterproofing system, number of coats and the height up the walls?
- Are corner treatment and pipe collars listed?
- Is a pond test included, and how long?
- Is epoxy grout specified?
Already have quotes? Membrain can compare them on scope, not just price. Planning the work instead? A written specification makes quotes comparable.
How this guide is built
Diagnostic basis
Membrain separates visible signs from possible water-entry mechanisms, then asks for evidence that can distinguish the remaining causes.
Repair-source governance
Public guides stay brand-neutral. When Membrain creates a repair plan, methods and products come from current approved manufacturer documents in its technical library.
Evidence limits
A photo cannot confirm concealed pipes, waterproofing layers or moisture depth. When remote evidence cannot separate the causes, a site inspection is the correct next step.
Technical notes behind this guide
Deeper reasoning on the moisture patterns and water-entry mechanisms used to interpret this problem.
Naye bathroom mein tiles se pehle waterproofing kaise ho?
Tiles lagne ke baad waterproofing dikhti nahi, isliye har step apni aankhon se dekho: corner aur pipe ke collar, deewar pe kam se kam do coat, aur drain ki taraf dhalaan.
Tiles se pehle pond test zaroor karwao: drain band karke 24 ghante paani bhar ke rakho aur neeche check karo.
Frequently asked questions
Is bathroom waterproofing needed in a new flat?
Yes. A bathroom without a proper waterproof layer under the tiles will eventually leak into the room below or beside it.
How high should the waterproofing go on the walls?
Usually about 300 mm above the floor around the room, and to full height in the shower area.
How long should the pond test run?
At least 24 hours, with someone checking below and beside the bathroom before tiling starts.
Planning the work?
Tell Membrain what you are building and get the right waterproofing method for each surface, with the checks for every stage, before work starts. Free to start.
Remote guidance, not a site inspection.