Bathroom refurbishments carry more consequence for a badly specified job than almost any other trade on this site, because water finding its way past a poorly detailed shower tray or wet room floor doesn't just look bad — it can damage the ceiling and joists of the room below. This is a job where the specification genuinely protects you, not just your budget.
The written quote should name the tanking system, confirm falls to waste are correctly set out, and list the waste and overflow components rather than treating plumbing as a single vague line.
Tanking system and coverage
The tanking product (a liquid tanking membrane or a tanking board system) should be named, along with exactly where it's applied — shower enclosure walls and floor as a minimum, and ideally the whole bathroom floor and any walls with a water source. A quote that just says 'waterproofed' without naming the product or its coverage area is leaving the most safety-critical part of the job undefined.
Corners, upstands and any pipe penetrations through the tanking need specific detail (tanking tape and corner pieces at joints) since these junctions are the most common place a tanking system fails if rushed.
Falls to waste and wet room floor build-up
For a walk-in shower or wet room, the floor needs a fall built in towards the drain — this is a structural and screed detail, not just a tiling one, and the quote should confirm how the fall is formed (a pre-formed shower tray, a formed screed fall, or a linear drain system) and to what gradient.
Wet room floor build-up in an upstairs bathroom (common in a loft conversion en-suite) needs particular care around the joist structure and any additional waterproofing at the floor-to-wall junction, given the room below is directly exposed to any failure.
Waste and overflow sets
Waste, trap and overflow components for the bath, basin and shower should be named by type (compression waste versus push-fit, and whether traps are accessible for future clearing), since these unglamorous fittings are exactly what a cheap quote lumps into a vague 'plumbing allowance'.
Access panels for bath and shower waste connections should be specified in the design, since sealing these away completely makes any future leak or blockage far harder to diagnose and fix.
Ventilation and extraction
An extractor fan rated for the room size, ducted to outside air rather than into a loft void, is a building regulations requirement in a bathroom without adequate natural ventilation, and the quote should state the fan's extraction rate and duct route. Poor ventilation is one of the most common causes of mould and finish failure in bathrooms refurbished on a budget.
What cheap quotes leave out
Underfloor heating first-fix if included, tile trims and movement joints at wall-floor junctions, and confirmation of who's responsible for isolating and reconnecting water supplies during the works are common gaps. Any work on gas (a combi boiler move) must be carried out and certified by a Gas Safe registered engineer, and the quote should state this explicitly rather than folding it into general plumbing.
Common questions
What is tanking and why does it matter?+
Tanking is a waterproof membrane or board system applied under tiling in a shower or wet room to stop water penetrating into the structure behind. It's the single most important defence against leaks reaching the ceiling below, so the quote should name the exact product and where it's applied.
Does a wet room floor need a special fall?+
Yes — water needs a built-in gradient towards the drain, formed either with a pre-formed tray, a screeded fall, or a linear drain system. This is a structural and screed detail that should be specified, not left to the tiler to work out on the day.
Why does bathroom ventilation matter for the finish?+
An underpowered or poorly ducted extractor fan lets moisture build up, which is a major cause of mould, peeling paint and grout failure in bathrooms. Building regulations require adequate ventilation, and the quote should state the fan's rating and duct route.
Who should move a combi boiler during a bathroom refurbishment?+
Only a Gas Safe registered engineer can legally carry out and certify that work. The quote should state clearly that this is being arranged with a qualified specialist rather than treated as general plumbing.
Get your bathroom refurbishment properly specified
We name the tanking system, falls and waste sets in writing, coordinated with Gas Safe and Part P registered trades where needed.