Bathroom waterproofing in Portugal: what the law requires and what quotes leave out

If you are reading this because a quote mentions waterproofing “the shower area” and you suspect the rest of the bathroom is missing, your instinct is right. Portuguese law leaves no room for choice here: the entire floor and every wall up to 1.50 m must be waterproof, not only the wall the water hits directly. The requirement comes from the RGEU, Portugal’s general building regulation, in force since 1951, and it still applies every time a bathroom is rebuilt.

This matters even to someone who will never open a building regulation, because this is precisely the part the tiles hide, and precisely where problems appear weeks or months after the job is signed off.

What the law requires, article by article

The RGEU (Decreto-Lei 38382/1951) treats walls and floors in separate articles, and both are unambiguous. The original Portuguese text, with a plain-English reading after each:

Article 31: “As paredes das casas de banho, retretes, copas, cozinhas e locais de lavagem são revestidas, até, pelo menos, altura de 1,50 m, com materiais de revestimento impermeáveis à água e humidade e de fácil limpeza.”

In short: walls in bathrooms, toilets, pantries, kitchens and laundry areas must be covered to a height of at least 1.50 m with materials that are impermeable to water and moisture and easy to clean.

Article 41: “Os pavimentos das casas de banho, retretes, copas, cozinhas e outros locais onde forem de recear infiltrações serão assentes em estruturas imputrescíveis e constituídas por materiais impermeáveis apresentando uma superfície plana, lisa e facilmente lavável.”

In short: floors in those same rooms, and anywhere else leaks are a concern, must be laid on rot-proof structures and built from impermeable materials with a flat, smooth, washable surface.

Note what each article says and what it does not. Article 31 sets a minimum wall height, 1.50 m, without distinguishing “shower wall” from “basin wall”: the requirement is identical throughout the room. Article 41, covering the floor, sets no zone at all. It refers to the whole bathroom, without exception.

Element	What the law requires	Where it applies
Floor	Impermeable material	The entire bathroom, no exempt zones
Walls	Waterproof to 1.50 m	Every wall in the room
Shower and bath area	No separate rule in the law	Standard technical reinforcement, not a separate legal zone

What usually gets left out

We read through the waterproofing guides published in Portuguese by companies in the trade. What they describe is technically sound: prepare the surface, apply the waterproofing, test for leaks before tiling. What they do not reach is the legal basis. No mention of the RGEU, of the 1.50 m height, or of the fact that the floor has to be treated in full. Anyone looking only at the finished result, with the tile already laid, has no way of confirming whether the layer underneath covers what the law asks or only the most obvious area.

That has a direct practical consequence: always ask, in writing, for waterproofing across the whole floor and up the walls to 1.50 m, not merely “the shower area”. A quote that describes the work in that reduced way is describing less than the law requires.

The shower area gets more reinforcement, but it is not a separate zone

One common confusion is worth clearing up. It is standard practice to reinforce the direct-spray area, typically taking the waterproofing to ceiling height on the shower wall, or above the rim of the bath, rather than stopping at the legal 1.50 m. That is not the law asking for more in that spot. It is sound technique responding to where the water hits hardest and most often. On the remaining walls, with no direct spray, the 1.50 m of article 31 already meets the minimum.

Three points concentrate most of the risk, and any properly applied system treats them with particular care:

1. Wall-to-floor joints. This is where two separately waterproofed surfaces meet, and one badly sealed joint here cancels out the waterproofing on both. The fix is elastic sealing tape bedded into the waterproofing product itself, not stuck over the top once it has dried.
2. Corners and angles. Same reasoning as the joints: these are changes of plane, where the membrane has least room to stretch and cracks first as the building settles.
3. Drain and pipe penetrations through the floor. Every hole through the waterproofing is a potential leak path unless it is sealed with the correct accessory, usually a collar or sleeve belonging to the system in use.

What it costs

As a standalone job, without the rest of a renovation around it, the Portuguese market works with clear reference figures:

Item	Reference price
Wall waterproofing	~7 €/m²
Floor waterproofing	~20 €/m²
Full bathroom (~6 m²)	250 to 300 €

That is the cost of waterproofing on its own, not of a full renovation. In a job that also includes demolition, plumbing, tiling and fixtures, this item falls inside that job’s wider range: between 2,500 and 14,000 € for a reference bathroom of 5 m², depending on the finish level. It is not a figure added on top of that range; it is a slice of it.

How it is applied, and why curing time is not negotiable

In renovation work the most common products are liquid membranes applied by brush or roller (polyurethane or modified cement-based) and two-component systems (cement plus resin) in areas of direct water contact. Brands with a strong presence in the Portuguese market, such as Sika, Mapei and Weber, publish their own systems for this use, all following the same underlying logic:

1. Prepare the surface. The substrate must be clean, dry and free of visible cracks. Existing cracks are sealed before any waterproofing goes on, never coated over.
2. Reinforce joints, corners and drain connections with elastic sealing tape bedded into the product, as described above.
3. Apply the first coat by brush or roller and respect the drying interval the manufacturer specifies.
4. Apply the second coat across the first, at right angles to it, to eliminate any gaps in coverage.
5. Let it cure completely before moving on. This step, not the ones before it, is what most separates a sound job from a problem waiting to happen.
6. Only then, lay the tile, using adhesives compatible with the waterproofing system underneath.

What fails is rarely the product. It is the timing. Each coat has a minimum drying interval, usually around 24 hours, and full curing before tiling can take several days with cement-based products. The surface can feel dry to the touch long before the layer has cured through. Tiling too early leaves no visible trace at handover: the problem only appears weeks or months later, once water has found its way through.

Worth remembering A quote promising the same bathroom in far less time than others of the same scope is almost always cutting somewhere in the curing times. It is the same logic we set out about renovation timelines: some waits cannot be compressed without consequences.

What it looks like when it fails

The classic symptom is not a puddle the day after the job. It is a leak into the ceiling of the flat below, mould behind the skirting, or damp climbing a wall months later, by which point nobody connects the problem to the work that was done. Repairing an established leak costs around 225 € on average, but that figure usually covers the visible symptom only. Fixing the cause almost always means breaking up tile that has already been laid, redoing the waterproofing from scratch and retiling, which costs far more, in money and in disruption, than doing it properly the first time.

This is also the reasoning behind something we set out on the bathroom page: treating waterproofing and under-tile plumbing with their own explicit guarantee in the contract, rather than letting them dissolve into a generic warranty on “finishes”. The part that ends up hidden is the part that most often fails, which is exactly why it deserves a separate written commitment.

What to confirm before signing the quote

Since the person paying never sees what goes under the tile, the only way to confirm the work meets the law is to ask for this in writing before the job starts:

1. That the description covers the whole floor, not “the shower area” or “the wet zone”.
2. That it covers walls to 1.50 m, throughout the bathroom, not only beside the shower or bath.
3. Photographs of the work before tiling. A contractor confident in the job has no reason to refuse recording that stage, and it is the only visual evidence that survives once everything is covered.
4. An explicit guarantee for this stage, separate from the general finishes warranty, with a defined term in the contract.