Bathroom renovation in Dubai: why they fail and how to build one that lasts

Part two · HDi answers

The straight answer

Bathrooms fail for four reasons, almost always in this order: waterproofing that is missing, broken, or not sealed into the drain and up the walls; a floor without a true fall to the drain; extraction too weak to clear the steam; and pipework and joints buried with no way to reach them. You stop it with a continuous membrane over the whole floor and up the walls, sealed into the drain; a fall of about 1:80 to 1:100 formed in the screed; a flood test of 24 to 48 hours before a single tile goes down; and a ducted extractor of at least 25 litres a second that keeps running after you leave the room.

From what you describe, your bathroom has at least three of the four: water reaching the flat below, water standing by the glass, and mould and swelling from humidity that is not being taken out. Regrouting will not fix any of them, because grout is not a waterproof layer. The shower floor has to come up. Here is why, and what has to happen instead.

Why bathrooms fail: the four causes

1. The waterproofing

Tiles and grout are a finish, not a seal. Grout is porous, and water passes through it every time you shower. What keeps that water out of the slab, and out of your neighbour's ceiling, is the membrane underneath. When a bathroom leaks into the flat below, the cause is nearly always one of these:

• No membrane at all, or only a coat of something under the shower area.
• A membrane that stops at the floor, so water running down the wall tiles gets behind it at the corner.
• A membrane not sealed into the drain. This is the commonest one. The drain body needs a flange or clamping ring the membrane bonds or clamps into. Without it, water that gets under the tiles runs round the outside of the drain and into the slab.
• Corners and pipes not reinforced. Wall-to-floor and wall-to-wall junctions move slightly, and an unreinforced membrane cracks there.
• Too thin, or put on in one coat when the maker's instructions call for two at a set thickness.

2. The falls

Water leaves by gravity. The screed under the tiles has to slope to the drain across the whole wet area, at around 1:80 to 1:100, which is roughly 10 to 12 mm for every metre. Your puddle by the glass is a fall fault: the floor is flat or back-falls in that spot. Standing water finds every weakness in the grout and the membrane, all day.

3. The extraction

A shower in a Dubai bathroom, with the air conditioning cooling the walls, puts moisture into the room that has to be taken out. If it is not, it condenses on the ceiling and grout, and that is your mould, your swollen door frame and your vanity. The widely used ASHRAE residential ventilation standard asks for about 25 litres a second (50 cubic feet a minute) from a bathroom extractor running when the room is used, or about 10 litres a second running continuously. A small fan into a blocked or undersized duct moves a fraction of that.

4. Pipework and access

A concealed shower valve, a rainfall head pipe or a concealed cistern that leaks inside the wall soaks the wall and the floor from behind, and no membrane on the room side stops that. Every buried joint should have been pressure-tested before the walls were closed, and the valve and cistern need an access route.

Why regrouting will not fix it

Regrouting and new silicone make a shower look clean for a while, and they slow water down slightly. They do nothing about water already under the tiles, a drain that was never sealed to the membrane, a floor that does not fall, or a room that cannot get rid of its steam. The stain below will come back, and the building has asked for proof the problem is fixed. AED 2,500 spent on regrouting is AED 2,500 spent before the real repair.

Before anything is taken out, though, find the source. A good contractor tests in stages: the drain and floor with the shower off and water poured onto the floor only; the walls and screen by running the shower against them; and the supply pipework with a pressure test. That tells you whether you are fixing the floor, the walls, the pipes or all three, and gives the building manager a written answer.

Doing it properly: the sequence

1. Strip to the structure. Tiles, screed and old membrane off in the wet area, so the slab can be inspected and dried.
2. First fix and pressure test. New supply pipework, valves and wastes, every joint tested by holding it above working pressure for a set period with no drop, before anything is closed in.
3. The drain. A drain body with a proper waterproofing flange or clamping ring, set at the right height for the screed and the fall.
4. Screed to falls. The fall formed in the screed, not built up in tile adhesive, and allowed to cure.
5. Membrane. A liquid-applied or sheet membrane system, tested to the European standard for waterproofing under tiles (EN 14891) or an equivalent, over the whole floor, sealed into the drain, turned up every wall at least 150 to 200 mm, and up the full height of the shower area. Reinforcing tape in every corner, collars round every pipe, two coats where the maker says two, each at the stated thickness.
6. Flood test. Drain plugged, floor filled, left 24 to 48 hours, flat below checked. No tiles until it passes, photographed and dated.
7. Tiling with epoxy grout in the shower, flexible adhesive suited to large porcelain tiles, and silicone, not grout, at every internal corner and change of plane.
8. Extraction ducted out, on a run-on timer or a humidity sensor, with an air path into the room.
9. Water test at handover. A bucket across the finished floor: every drop reaches the drain, and the floor is dry within minutes.

Steps five and six are the ones you will never see again, so they are the ones to insist on. Put them in the contract as hold points: no tiling until the membrane has been photographed and the flood test has passed.

Can you still have a walk-in shower?

Very likely yes, but whether it can be truly level with the rest of the floor depends on depth, not on design.

• A level-access floor needs depth for the fall. Across 1.2 metres at 1:80 the screed drops about 15 mm, on top of a minimum screed thickness and the depth of the drain body. That depth has to come from somewhere.
• In many Dubai towers it cannot come from the slab. Many floors are post-tensioned concrete, where cutting or chasing the slab is not allowed without the structural engineer's approval. Never let anyone break into an apartment slab on their own judgement.
• So it often comes from the floor finish. Low-profile linear drains, a slight rise in the bathroom floor at the door, or a very shallow step into the shower all work. A linear drain along the back wall lets the whole shower floor fall one way, which suits large tiles.
• A full wetroom, with no screen, needs the fall across a larger area, a bigger waterproofed zone and stronger extraction. A shower with a fixed glass panel gives almost the same look with far less risk.

In an apartment, the building will want an NOC for a bathroom refit, and moving a toilet or a drain position is a bigger job that brings in a permit. Our guide to renovation approvals in Dubai covers the order.

Materials that survive a Dubai bathroom

• Large-format porcelain on floors and walls: non-porous, no sealing, and fewer grout lines.
• Epoxy grout in the shower. Cement grout absorbs water and soap and goes black, as yours has.
• Natural marble is a legitimate choice if you accept that shampoo, toothpaste and cleaners will etch it. It is not a low-maintenance one.
• Vanity carcass in moisture-resistant board, every edge banded and sealed, on legs or wall-hung clear of the floor. Your puffed vanity doors are standard board with open edges.
• Door frame and door in moisture-resistant material, with the frame sealed at the bottom where the floor is mopped.
• Taps and showers: Dubai water is hard, so choose finishes that tolerate limescale and cleaning. Matt black and brushed brass show marks more than the showroom suggests.
• Rainfall heads need flow as well as pressure. Check what the building delivers before choosing a large one, or it will drip rather than pour.

What it costs

Market guides for Dubai put a bathroom renovation at:

These are guides, not quotations, and the sources disagree at the edges. What the figures will not show is how much of the money is below the tiles. Strip-out, pipework, drain, screed, membrane and testing are a real share of an honest price, and they are exactly where a cheap quotation saves money. A quotation that says "supply and fix tiles" and nothing about waterproofing has priced the part you can see.

Add the cost of making good the ceiling below, and a contingency for what the strip-out reveals in a bathroom that has already leaked.

How to know it was done when you cannot see it

1. Photographs of the bare slab, the new pipework and the pressure test.
2. Photographs of the drain flange, the membrane, the corner tape and the pipe collars, with the product named.
3. The flood test photographed at the start and the end, with the date, and the flat below checked.
4. The fall checked with a level before tiling, and a bucket test at handover.
5. The extractor's rate and run-on timer shown working at handover.
6. Access to every concealed valve and cistern, shown to you.
7. A written warranty on the workmanship, from the company named on the contract.

Your questions, answered one by one

Why did ours fail?

On the evidence, the membrane is not sealed into the drain or is missing at the shower, the floor does not fall towards the drain by the glass, and the extraction is not taking out the steam. Testing in stages will confirm which.

Will regrouting fix it?

No. It may hide it for a few months.

Does the whole room have to come out?

The shower floor and the wet walls, almost certainly. The rest depends on what the tests and the strip-out show. Where the room is being opened anyway, it is usually worth doing the whole floor once rather than patching.

Who pays for the flat below?

The building will look to you, as the owner of the unit the water comes from. You may then have a claim against the contractor who did the work, which is why the original contract, invoices and any warranty matter. Keep them, and keep a copy of the building's letter.

How HDi rebuilds a bathroom

We take a bathroom back to the walls and rebuild it: plumbing, waterproofing, tiling, lighting and a vanity made in our own factory in Dubai Production City. Our own MEP crew and our own installers do the work, so the waterproofing, the plumbing and the tiling sit with one team rather than three companies blaming each other.

After the site measure we send you your own bathroom in 3D, where you can try vanities, worktops, basins, taps and finishes, save your choices and send them back to your designer. Before work starts you receive your schedule from our portal, and during the job you get site photos and videos every day, so you can see the stages that end up under the tiles. At the end there is a joint snagging walk, everything put right, and a clean handover. The fit-out carries one year's warranty from handover, our handmade cabinetry three to five years depending on the finishes, and the manufacturers' warranties on fittings and hardware are handled by us.

The initial design consultation is AED 5,000, credited in full against your project when you approve it, and it is where we look at what has failed and tell you what has to come out.

Dealing with a leak, or planning a bathroom that never has one? Book a consultation or call 050 578 1086. We will tell you what has failed, what has to come out and what it will take to do it once.