How to Plan a Bathroom Remodel: The UK Guide to Layout, Costs and Order of Work

The bathrooms that go badly wrong are rarely the ones with the wrong tile. They are the ones where somebody moved the WC 900mm without checking where the soil stack was, or specified a rain head on a gravity system that delivers eight litres a minute. Both decisions take ten minutes on paper, and both add thousands.

So before you look at a single suite, work out which job you are taking on. There are three distinct bathroom projects in UK housing stock, and each plans differently.

Read these in order and stop at the first one that describes you. Budget, trades, timeline and whether Building Control gets involved all follow from that tier. A Tier 2 refit costs two to three times a Tier 1 refresh; Tier 3 adds another 40-60% for the same fittings.

• •Tier 1 — refresh: layout identical, sanitaryware sound. Regrout, reseal, new taps, new lighting, paint. Two to four days, £400-£1,500.
• •Tier 2 — like-for-like refit: same positions, new everything. New wastes meet the old ones where they are, so no first-fix drainage. Five to ten working days.
• •Tier 3 — re-plan: something moves more than about 300mm, or you are knocking through or going wet room. You now need to know where the 110mm soil stack is, which way the joists run, and whether the hot water system copes. Two to four weeks.
• •Overriding all three: recurring black mould, blown plaster behind the bath or a springy floor mean ventilation failure, a long-term leak or joist deflection. Fix those first or they will destroy the new bathroom.

Anything touching gas is Gas Safe registered work, full stop. Unvented cylinders fall under Building Regulations Part G3 and need a competent-person qualification. Electrical work in the zones around a bath or shower is notifiable under Part P in England, and wider in Wales — use a registered electrician who self-certifies, because you will want that certificate when you sell.

• •Textured ceiling coatings in homes decorated before 2000 may contain asbestos. Do not sand or scrape — test it (£30-£60 a sample) or overboard it.
• •Check the internal stop tap actually shuts before demolition day. Seized stop taps are the commonest reason a strip-out becomes a flood.
• •Lock off the shower or immersion circuit at the consumer unit, not just the pull-cord, and expect lead or galvanised pipework in anything pre-1970.

You cannot plan a bathroom you have not measured properly, so the planning kit comes first.

• •Planning: 5m tape, laser measure (£25-£50), spirit level, graph paper for a 1:20 plan, cable and pipe detector (£30-£60), a jug and stopwatch for flow rate.
• •Strip-out: goggles, dust masks, floor protection, basin wrench, and a 4-yard skip at £180-£280.
• •Long lead times: order sanitaryware, enclosures and tiles 4-8 weeks ahead, plus 12-15% extra tiles from the same batch.
• •Substrate beats tile choice: backer board (£25-£40 a sheet) on stud walls, 18-22mm WBP ply or decoupling matting on suspended timber floors.

For a typical 2.4m x 1.7m bathroom, a like-for-like refit lands between £4,500 and £8,500 all in. Mid-spec with a decent enclosure and porcelain floor runs £8,500-£13,000; a re-plan with a moved WC starts around £13,000 and reaches £20,000+ in London. Labour is 50-60% of that — our breakdown of bathroom refit costs has the itemised figures.

Day rates to check quotes against: fitter £220-£320, tiler £200-£300 or £35-£55 per m², electrician £250-£400, plumbing £45-£75 an hour outside London. A two-person team does a like-for-like refit in 5-10 working days; the same job DIY, evenings and weekends, takes 4-8 weeks with no bathroom for most of it, so plan where everyone washes before day one.

Work through these in order. Jumping to step 7 is how people end up with a bath that will not fit through the door.

• •1. Draw the room at 1:20 — wall lengths at floor and at ceiling (they differ in older houses), window, door swing, ceiling height.
• •2. Find and mark the soil stack. A 100mm WC branch runs 6m to the stack at most; 40mm basin and bath wastes need roughly 1:40 fall. Break either and it is a macerator or a new layout.
• •3. Establish the hot water system — combi, vented gravity cylinder or unvented. Time a jug at the bath tap: under 10 litres a minute means a rain head will disappoint.
• •4. Choose bath, shower or both. Losing the only bath hurts resale in a family house; in a 1.7m-wide room a walk-in shower buys more space than a shower over bath.
• •5. Check real clearances: 700mm in front of the WC, 200mm from WC centreline to a side wall, 550mm at the basin.
• •6. Plan ventilation and electrics together. Building Regs want 15 litres per second of extract minimum, ducted outside, never into the loft. Specify IP-rated fittings for zones 1 and 2 now.
• •7. Pick finishes, checking the slip rating underfoot; our comparison of bathroom flooring options covers what survives standing water.
• •8. Write a schedule of works in sequence: strip out, first fix, boarding, tanking, tiling, second fix, test, decorate, seal.
• •9. Get three itemised quotes against that document — comparing estimates properly separates value from gut feel.
• •10. Add 15-20% contingency for what appears when the bath comes out: rot, lead pipe, a butchered joist.
• •11. Confirm delivery dates before booking the fitter, then snag before final payment — run every outlet, check falls, test the fan, inspect the silicone in daylight.

If mould has been persistent, new tiles will not fix it — the cause is weak extraction or a cold external wall, and it will bloom on fresh grout within a winter. Sort out why bathroom mould keeps returning first.

• •Joists running the wrong way for the new waste: accept a 40-70mm raised deck, or leave the fitting put. Never notch a joist deeper than an eighth of its depth.
• •Boxing in the stack and pipework eats 100-150mm of wall. Draw it before buying a 1700mm bath for a 1750mm space.
• •Sloping ceilings need 2m headroom measured at the shower centre, not the door, and a springy floor cracks grout — overboard or decouple it.
• •A combi cannot run bath and shower at once: a cylinder question, not a shower head one.

There is real DIY in a bathroom: stripping out, tiling, decorating, fitting cabinets, replacing silicone. There is also work where getting it wrong means a flooded ceiling or a failed sale. Hand over gas, unvented cylinders, altered circuits in the bath and shower zones, moving the soil stack, removing a wall, and tanking a wet room over timber — a tanking failure hides for months, then costs more than the bathroom did.

If you landed in Tier 3, one main contractor coordinating the trades is usually worth the 10-15% management premium. Print our bathroom refit checklist and mark every line DIY, trade or undecided before you commit a penny.