After 12 years and thousands of bathrooms, we could write a book about mistakes
But since nobody would read a 400-page book about damp and badly sealed joints, here’s the short version: the 10 mistakes we see most often. Week after week. In renovations done by “professionals” and in weekend adventures that end with the bathroom worse than it started.
These aren’t rare mistakes. They aren’t extreme cases. They’re things that happen in normal flats in Valencia, Torrent, Paterna and surrounding areas. Every Monday, when our team reviews the previous week’s visits, the same patterns emerge. Again and again.
If you’re thinking about renovating your bathroom — or if you’ve already received a quote and have doubts — read this through completely. It’s 12 minutes that could save you thousands of euros and a lot of grief. And if you want a quick estimate of what your renovation should cost, start with our calculator: in 2 minutes you’ll have a real indicative price.
Let’s get to it.
Mistake 1: Not waterproofing properly (or not waterproofing at all)
Mistake number 1 makes our hair stand on end. Without waterproofing, your new bathroom has an expiry date. And that date is usually “between 6 months and 2 years.”
Last month, in a flat in Patraix, we stripped out a bathroom that another “professional” had finished 8 months earlier. The waterproofing didn’t exist. Literally. Under the shower tiles there was bare brick — no membrane, no liquid coating, nothing. The wall of the adjacent bedroom already had a damp patch the size of a dinner plate.
What the regulations say
The Spanish Technical Building Code (CTE) establishes in its Basic Document HS1 (protection against moisture) the minimum waterproofing requirements for wet areas. It’s not a suggestion: it’s mandatory. Every enclosure delimiting a habitable space with water installations must have a waterproof barrier.
What should be done
In a shower, waterproofing must cover the entire floor of the shower tray and extend up the walls a minimum of 20 cm above the highest splash point. In practice, we take it all the way to the ceiling in the shower zone. The material can be liquid polyurethane membrane, bituminous sheet or waterproof panel systems like Wedi or Schluter-DITRA.
The cost of properly waterproofing a shower is around €200-500. The cost of repairing water damage can exceed €5,000 — not counting the claim from your downstairs neighbour.
Mistake 2: Choosing tiles before having a clear layout design
Honestly, the number of times someone turns up with three boxes of tiles bought on sale asking us to “put together something nice with these.”
The tile is the consequence of the design, not the other way round. First you define the layout: where the shower goes, where the toilet goes, where the vanity unit goes, where the pipes run. Then you choose format, colour and pattern.
Why the order matters
- Formats determine joints and cuts. A 120x60 tile on a 2.10 m high wall needs three pieces and a half-cut. A 75x75 might not fit any dimension of your bathroom.
- The pattern affects the perception of space. Horizontal laying elongates; vertical stretches upward.
- Corners and junctions dictate. If you choose before measuring, you’ll end up with ugly cuts or half-tiles in corners visible from the doorway.
The Spanish Association of Tile and Floor Covering Manufacturers (ASCER) publishes technical guides on formats and installation systems that detail how to plan correct layouts. It’s worth taking a look before buying a single square metre.
If you’re comparing tile options, our guide on cheap vs expensive bathroom materials helps you decide where it’s worth spending more and where it isn’t.
Mistake 3: Forgetting about ventilation and extraction
A bathroom generates between 2 and 4 litres of water vapour per shower. If that steam has nowhere to go, it condenses on walls, ceiling and joints. In three months you’ll have black mould in the corners. In a year, the grout is rotten and it smells musty.
What you need at minimum
- Bathroom with a window: the window alone isn’t enough if you don’t open it after every shower (nobody does in winter). Install an extractor fan anyway.
- Interior bathroom without a window: mechanical extractor fan, mandatory. Preferably with a humidity sensor so it starts automatically when it detects condensation.
- Minimum flow rate: the CTE requires 15 l/s for bathrooms. An extractor fan under 90 m³/h won’t reach that.
The cost of a good extractor fan with timer and humidity sensor is between €80 and €250. You simply can’t justify not fitting one when a bathroom renovation is costing you €6,000-12,000. Read the technical details in our guide on bathroom ventilation to prevent damp.
Mistake 4: Wrong slope on the shower tray (water doesn’t drain)
If water pools in the shower, something has gone wrong. And if it pools every time you shower, something has gone very wrong.
In wet-room showers — those built on the structural floor with mortar and tile — the slope towards the drain must be 1.5% to 2%. That means for every linear metre, the floor drops between 1.5 and 2 centimetres towards the drain. It seems small, but the difference between 1% and 2% is the difference between a permanent puddle and a shower that drains in seconds.
What we often see
- Insufficient slope: the water takes half a minute to drain. You end up showering with your feet in a 2 cm puddle.
- Slope in the wrong direction: water flows towards the shower screen door instead of the drain. No comment.
- No slope: completely flat wet-room base. Water spreads across the entire surface and only drains if you push it with your foot.
A good tiler can do this with their eyes closed. A bad one doesn’t even consider it. Make sure the quote specifies the formation of falls in the shower zone — if it doesn’t mention it, ask before you sign.
Mistake 5: Cheap plumbing hidden behind expensive tiles
Let’s be clear: you don’t see the pipes. They’re behind the wall, under the floor, embedded. So the temptation to save money there is enormous. After all, they’re not visible.
Until they burst.
A quality cross-linked polyethylene (PEX) pipe costs a few cents more per metre than a generic one. An AENOR-certified brass fitting costs €2-3 more than an unbranded one. Across an entire bathroom, the difference between good plumbing and mediocre plumbing can be €100-200.
The cost of repairing a leak in an embedded pipe starts at €800. If you need to hack through tiles to access it, multiply by three.
Signs your plumber is cutting corners
- Not using certified multilayer or PEX pipe.
- Joints made with glue instead of press fittings.
- No pressure test before closing up the walls.
- No individual shut-off valves for each water point.
If you have doubts about the condition of your current plumbing, read our guide on when to replace your bathroom pipes.
Mistake 6: Insufficient or poorly placed sockets
Hairdryer, hair straightener, electric razor, electric toothbrush, aroma diffuser, Bluetooth speaker for singing in the shower. How many sockets do you have? One? Behind the vanity unit where you can’t reach?
What you need in a 2026 bathroom
- Minimum 2 power sockets by the mirror/basin, at a height of 110-120 cm and more than 60 cm from the shower or bath.
- 1 power socket for the extractor fan if it’s not hard-wired.
- 1 additional power socket if you have an electric towel rail or connected backlit mirror.
- All with minimum IP44 protection (zone 2 of the REBT regulations).
Installing a light point or socket during the renovation costs €30-60. Installing one afterwards, once everything is tiled, costs €150-300 and leaves a mark on the tile that will stare at you every morning for the next 15 years.
Mistake 7: All white, all plain, all the same
The total white bathroom looks spectacular in Instagram photos. For three months. Then it becomes a hospital room that conveys nothing.
It’s not that white is bad. It’s that white alone, without contrast, without texture, without an element to break the monotony, is boring. And on top of that, it shows every bit of dirt: every limescale drop, every hair, every fingermark is visible from the doorway.
Alternatives that work
- Neutral base + colour accent. Light-toned walls and a panel of tiles in forest green, petrol blue or terracotta. A touch that adds personality without taking too much risk.
- White with textures. Zellige-style tiles or relief hydraulic tiles. All white but with visual movement.
- Different floor from walls. Wood-tone or dark grey floor, light walls. Creates depth and warmth.
- Taps and accessories as contrast. A matt black or brushed gold tap against a white background transforms the entire bathroom for €200.
Manufacturers like Roca have complete collections with warm tone finishes and natural textures that combine with white bases without falling into clinical coldness.
Mistake 8: Not planning storage (no niche, no shelves, no decent vanity unit)
You move in, organise the new bathroom, put everything in its place… and two weeks later you’ve got shampoo bottles on the shower floor, moisturiser on top of the cistern and the hairdryer hanging from the door handle.
People think of the bathroom as a beautiful space but forget it’s a functional space. Everything you use daily needs a fixed place.
The minimum a bathroom should have
- Shower niche: a recess built into the wall, minimum 30x30 cm, for shower gel, shampoo and sponge. It’s done during the renovation for €60-120. Afterwards, you can’t add one.
- Vanity unit with drawers: not open shelving (collects dust and clutter), not a pedestal (zero storage). Drawers. At least two.
- Mirror with cabinet: if you have space, a mirror-cabinet doubles storage without taking up floor space.
- A towel rail that works: not a decorative ring that only fits a hand towel. A bar rail that fits at least two bath towels.
This is planned in the design phase, not once the tiles are up. If you want to see how we handle it, take a look at how our process works — the preliminary design includes all of this.
Mistake 9: DIY tiling (“it looks easy on YouTube”)
Look, we love it when people do things with their hands. Assembling IKEA furniture, painting a wall, changing a tap. Go for it.
But tiling a bathroom isn’t the same as laying laminate flooring. Tiling a bathroom involves: precise cutting of ceramic pieces, handling spirit levels and plumb lines, surface preparation, applying adhesive with a notched trowel (and knowing which trowel to use for each format), forming uniform joints, perimeter silicone sealing, prior waterproofing, and junctions with sanitary ware and concealed fittings.
What goes wrong in 90% of DIY attempts
- Irregular cuts: where the tile meets a pipe, a socket or a corner. Without a wet-cut disc cutter and a steady hand, forget it.
- Crooked lines: a 2-millimetre offset in the first row becomes a centimetre by the time you reach the ceiling. And it shows. It really shows.
- Uneven joints: some 1 mm, others 3 mm, the odd one 5 mm. It looks like the tiles are dancing.
- Tiles coming loose: because the adhesive was wrong, the mix had too much water, or the substrate wasn’t cleaned before application.
A professional tiler in Valencia charges between €18 and €28 per square metre, depending on the format and complexity. In a 5 m² bathroom, that’s between €350 and €700 in labour. Is it really worth the risk to save that amount on a €6,000-10,000 renovation?
Mistake 10: Choosing the cheapest quote without reading what’s included
This is the mistake that triggers all the others. You receive three quotes: one for €5,800, another for €7,200 and another for €9,100. You choose the €5,800 one because “it’s the same work.” But it’s not the same work.
What’s usually missing from the cheapest quote
- Waterproofing: they don’t mention it because they’re not going to do it.
- Waste removal: “that’s extra.”
- Final cleaning: “that’s extra too.”
- VAT: that 10% or 21% that doesn’t appear in the headline number.
- Fixing and sealing materials: silicone, waterproof tape, fixings. They seem like details, but they add up to €150-250.
- Plumbing pressure test: they don’t do it, don’t charge for it, and if there’s a leak you find out when everything’s closed up.
- Written warranty: if it’s not in the quote, it doesn’t exist.
A transparent quote should have, at minimum, an itemised breakdown: demolition, plumbing, electrics, waterproofing, tiling, sanitary ware, taps, shower screen, vanity unit and cleaning. If you receive a single-line quote that says “full bathroom renovation: X euros,” be suspicious. Read our real breakdown of a bathroom renovation budget to know exactly what each item should include.
And if you receive quotes that don’t add up, check our guide on how to detect bathroom renovation scams to identify warning signs before signing anything.
How to avoid ALL these mistakes: the Reformarte method
You don’t need to become a construction expert. You need to work with someone who has a clear process. Here’s how we do it:
1. Free technical visit. We measure, photograph, assess the condition of the plumbing and electrics, identify potential hidden problems. Before talking about design, we know exactly what we’re working with.
2. Preliminary design with a fixed layout. Before choosing a single tile, we define the layout: where each element goes, where the pipes run, how many sockets you need, where the niche goes. You see all of this on a plan before work begins.
3. Fixed, itemised quote. Item by item, material by material. The price we give you is the price you pay. No surprises, no “extras” that appear mid-project.
4. Waterproofing, always. On every one of our projects. Without exception. With material certification and photographic documentation before covering up.
5. Certified plumbing and electrics. Pressure test on pipes before closing walls. Electrical certificate where required. Certified materials.
6. Real written warranty. Not a verbal promise. A document with years of coverage, what it includes and how to claim.
Want to see how the complete process works step by step? Visit how it works. And if you need a first price indication, use the calculator and in 2 minutes you’ll have a figure tailored to your bathroom.
Frequently asked questions
What is the most expensive mistake in a bathroom renovation?
Lack of waterproofing, without any doubt. Repairing water damage caused by missing or deficient waterproofing can cost between €3,000 and €8,000 — and that’s only counting damage to your property. If the water reaches the neighbour below, the bill can easily double with the insurance claim.
Is it possible to do an error-free bathroom renovation on a tight budget?
Yes, but a tight budget should cut costs on finishes, not on infrastructure. You can choose tiles at €12/m² instead of €35, a vanity unit at €300 instead of €800, or a standard shower screen at €250. What you can’t cut is waterproofing, plumbing or electrics. Read our guide on cheap vs expensive materials to know exactly where to save without compromising quality.
How do I know if a renovation quote is well prepared?
A professional quote should include: itemised breakdown (demolition, plumbing, electrics, waterproofing, tiling, sanitary ware, taps, shower screen, vanity unit, cleaning), material specifications (brand, model or equivalent), estimated execution timeline, payment terms, and warranty. If your quote doesn’t have all of this, ask for clarification before signing.
Is it worth renovating the bathroom myself to save money?
It depends on which part. Painting non-tiled areas, changing accessories (toilet roll holders, towel rails) or assembling a vanity unit are manageable tasks. But plumbing, electrics, waterproofing and tiling require technical knowledge and specific tools. A mistake in any of these areas can cost you more than the savings — and much more than hiring a professional from the start.
How much does it cost to renovate a bathroom avoiding all these mistakes?
In Valencia and surrounding areas, a full renovation of a 4-6 m² bathroom with all work properly executed — including waterproofing, certified plumbing, updated electrics and mid-range materials — ranges between €5,800 and €9,500 including VAT. If you want a figure more tailored to your specific bathroom, our calculator gives you a range in 2 minutes. You can also check our article on how much it costs to renovate a bathroom in Valencia in 2026 for detailed ranges.
Your bathroom deserves to be done right
The mistakes you’ve read about aren’t exaggerations. We see them every week. Some we fix, others we prevent. We prefer the latter, and so should you.
If you’re thinking about renovating your bathroom and want to do it once, well, and without surprises, we’re here. Calculate the cost of your renovation in 2 minutes, check our warranty and, when you’re ready, let’s talk.
And if you’re in Valencia or surrounding areas, even better. That way we can show you finished renovations in person. Because there’s no better argument than seeing it with your own eyes.
