There’s an assumption most people make about new build properties — that because everything is brand new, everything has been done properly. In our experience, when it comes to bathrooms, that assumption is almost always wrong.
A job in Holmes Chapel last year brought this into sharp focus. The property was eighteen months old. The customer wanted the bath removed and an open plan shower fitted in its place. Straightforward enough brief — but before we’d even started, the cracked grout on the existing tiles told us something wasn’t right.
What we found when we opened the wall
Once the tiles came off, the picture was exactly what we’d suspected. The plasterboard behind them was covered in black mould and was already breaking up. Eighteen months old. Never been touched since the builders handed the keys over.
The cause was straightforward. Water had been getting behind the tiles through the failing grout — cheap adhesive and grout applied without any waterproofing membrane underneath. Plasterboard, once water reaches it, behaves like a sponge. It absorbs moisture, swells, degrades, and provides the perfect environment for mould to take hold. It doesn’t take long. In this case, eighteen months was all it needed.
Before any new installation could go in, the damaged plasterboard had to come out completely, the area had to dry out properly, and everything had to be rebuilt from scratch with the waterproofing done correctly this time. A job that should have been straightforward became significantly more involved — and the customer was left paying to fix a problem that should never have existed in the first place.
The new build problem
In over 20 years of fitting bathrooms across Cheshire, we have never seen a large new build development where the bathroom has been properly tanked. Not once.
That’s worth sitting with for a moment. Tanking — applying a waterproof membrane before tiling any wet area — is a standard part of a professional bathroom installation. It’s not expensive, it’s not complicated, and it’s the single most important thing you can do to protect the structure of the room behind the tiles. And the large national developers simply don’t do it.
The reason is straightforward: volume and margin. On a large site development, the bathrooms are being turned around as quickly as possible. Tiles go straight onto plasterboard, adhesive and grout are the cheapest available, and the job is done. It looks fine on the day. The problems come later — often well within the first few years of the property being occupied.
It’s worth being fair here though. This isn’t a criticism of every builder. Smaller contractors doing bespoke one-off or two-off builds will often take a completely different approach — they have a reputation to protect in a way that a national developer operating at volume simply doesn’t. The issue is almost entirely specific to large site developments.
Why cheap grout fails so quickly
A new build property, for the first few years, is still moving. The structure is settling, there’s natural expansion and contraction as the building dries out, and that movement puts stress on everything — including the grout lines between tiles.
Cheap, rigid grout has no ability to flex with that movement. It cracks. Once it cracks, water gets in. And if there’s no waterproofing membrane behind the tiles to stop it, that water goes straight into whatever’s behind — usually plasterboard.
We use Mapei grout on every job specifically because it’s flexible. It can accommodate the small amounts of movement that every building experiences without cracking. In a new build that’s still settling, that flexibility isn’t a luxury — it’s essential. We also only ever use premium bagged flexible adhesive. Ready-mixed adhesive from a tub has its place, but it isn’t it in a wet area that needs to last.
What about the plasterboard itself?
Some people raise an eyebrow at plasterboard being used in a wet area at all. It’s a fair question, and the honest answer is that plasterboard is a perfectly acceptable background for bathroom tiling — provided it’s tanked correctly before anything goes on top of it. A proper waterproofing membrane means water never reaches the board in the first place, so the fact that it would absorb moisture if it got wet becomes irrelevant.
For those who want absolute belt-and-braces peace of mind, tile backer boards — such as Wedi board — are an alternative. They’re completely waterproof by nature and don’t need tanking in the same way. We’ll fit them where a customer specifically wants them. But in our honest view, if the tanking is done properly, the background material matters far less than people think. The membrane is doing the work.
What’s not acceptable — ever — is plasterboard with no tanking and cheap grout. Which is, unfortunately, what most new build bathrooms amount to.
If you’ve moved into a new build in the last few years
If you’re in a large development property and your bathroom is starting to show cracked grout — even if the property is only a year or two old — it’s worth taking seriously rather than just regrouting over the top. The grout cracking is a symptom. The question is whether water has already been getting behind the tiles, and what state the wall behind them is in.
We cover Holmes Chapel, Sandbach, Northwich, Middlewich, Knutsford and Winsford — all areas with significant new build development over the last decade. If you’re seeing early signs of problems in a newer property, give Martin a call on 07734 703414. We’ll give you an honest assessment of what’s there and what, if anything, needs doing.
Cheshire Bathroom Fitters — based in Middlewich, working across Cheshire for over 20 years.
