How to Plan a Bathroom Renovation in London: A Complete Guide

A standard London bathroom refit, stripped back to the walls and floor, usually takes two to four weeks on site. The tiling alone is often a week. Most of the delays come from things decided late: a vanity unit with an eight-week lead time, a shower tray that doesn’t match the waste position, or a change of layout after the first fix plumbing is in.

So most of the planning is about getting decisions made before anything is ripped out.

What’s usually behind a London bathroom

A lot of Victorian and Edwardian terraces were built without an indoor bathroom. Many had an outside WC in the yard, and baths were filled by hand. Bathrooms were added later, often in the back addition at the half landing or in a small back bedroom. That’s why so many London bathrooms are narrow, have a soil stack on the outside rear wall, and sit on timber joists that were never designed to carry a cast iron bath full of water.

Once the room is stripped, it’s common to find old lead or iron pipework, joists notched badly by previous plumbers, rot around the WC, and floorboards patched with chipboard. In 1950s to 1980s properties, textured ceilings and old floor tiles can contain asbestos and need testing before anyone sands or drills them.

None of this is visible at the quote stage, which is why a sensible budget keeps some money aside for what turns up under the floor.

Start with who uses it

A family bathroom used by four people between 7 and 8 in the morning needs different things from an en-suite for two. In the family bathroom, storage, a bath for small children and surfaces that are easy to clean usually come first. In an en-suite, people tend to want a bigger shower and less clutter.

The bath question comes up on almost every job. Some people take the bath out for a large walk-in shower and then miss it. Estate agents generally say a family house should have at least one bath, so if this is the only bathroom, think about that before removing it.

Cosmetic refresh or full renovation

A cosmetic update means new tiles, sanitaryware, taps and lighting, with the pipework and layout left where they are. A full renovation takes the room back to the joists and studs, reworks the plumbing and electrics, and rebuilds it with proper waterproofing.

If the layout already works and the pipework is in decent condition, keeping the positions of the WC, basin and bath saves a lot of money. If the room has never worked, or the floor bounces, or there are signs of water damage on the ceiling below, a cosmetic job just puts new tiles on old problems.

Budget

As a rough guide in London, a full refit of a mid-range family bathroom often comes to somewhere between £10,000 and £20,000. Higher-end finishes, a wet room or moving the WC can push that well past £25,000. Prices vary a lot between boroughs and between houses and flats.

The visible items, the tiles, taps, basin and shower, are often less than half the total. The rest is labour, plumbing, electrics, boarding, waterproofing, waste removal and making good. If the budget is tight, it’s usually better to choose plainer tiles than to cut the money spent on the waterproofing and the floor.

Layout and moving the plumbing

On a plan, a layout can look fine. In the room, small things go wrong: not enough space in front of the WC, a shower door that hits the basin, a towel rail where the door opens.

Moving the basin or the shower a short distance is usually manageable. Moving the WC is a bigger job. It needs a 100 mm soil pipe with a proper fall to the stack, and in a timber floor that pipe has to run between the joists or through them. Joists can only be notched or drilled in certain zones of the span, and only to a limited depth, so if the joists run the wrong way the WC may not be able to go where you want it. A macerator pump is the fallback, but it’s noisy and needs servicing.

Shower and bath wastes also need a fall. On a suspended floor a low shower tray can mean raising the floor or building a step. A level-access wet room on timber joists needs the floor cut down between the joists, a stiff ply deck, a formed fall to the drain and full tanking. It’s doable, but it’s not cheap.

In flats, the lease usually decides as much as the plumbing does. Moving a bathroom so that it sits over a neighbour’s bedroom often needs the freeholder’s consent, and some leases don’t allow it at all.

Water supply and hot water

Before choosing a shower, check the water pressure and flow at the property. Pressure varies a lot across London, and top-floor flats in older blocks can be poor. A rainfall head needs a decent flow rate to work properly.

Combi boilers are common in London flats. They’re fine for one bathroom, but run two showers at once and both suffer. Larger houses often have an unvented cylinder instead, which gives mains pressure hot water to several outlets. An unvented cylinder has to be installed by someone qualified to fit one, because of what the building regulations require of a stored hot water system:

“A hot water system that has a hot water storage vessel must incorporate precautions to— (a) prevent the temperature of the water stored in the vessel at any time exceeding 100°C; (b) ensure that any discharge from safety devices is safely conveyed to where it is visible but will not cause a danger to persons in or about the building.”

Building Regulations 2010, Schedule 1, Part G3(3)

That’s the reason for the tundish and the copper discharge pipe next to the cylinder. It has to run somewhere you can see it, so a fault gets noticed.

The same part sets a 48°C limit for hot water delivered to a bath. Read the wording carefully, though:

“The hot water supply to any fixed bath must be so designed and installed as to incorporate measures to ensure that the temperature of the water than can be delivered to that bath does not exceed 48°C.”

Building Regulations 2010, Schedule 1, Part G3(4)

The “than can be delivered” is in the published text as it stands. The limit itself applies only to new dwellings and to conversions, not to a refit in an existing house. A thermostatic mixing valve on the bath costs very little though, and with young children or elderly people in the house it’s worth fitting anyway.

There’s also a rule most people haven’t heard of. The Water Supply (Water Fittings) Regulations 1999 require you to tell the water company before installing certain fittings. On the list:

“a bath having a capacity, as measured to the centre line of overflow, of more than 230 litres”

Water Supply (Water Fittings) Regulations 1999, regulation 5, Table, item 4(a)

The same table covers some pumps and booster sets. In most of London that means notifying Thames Water. They have ten working days to respond, and if they don’t, consent is treated as given. Large freestanding baths are the ones that usually go over 230 litres, so check the capacity on the spec sheet.

London’s water and sewers have a history of their own. Most of the main sewers that take the bath water away were built by Joseph Bazalgette after the “Great Stink” of 1858, when the smell from the Thames got so bad that Parliament finally paid for a proper system. Many of those Victorian sewers are still in use.

Ventilation

Mould on the ceiling and black silicone around the bath usually mean the extraction isn’t doing its job. The legal requirement is short:

“There shall be adequate means of ventilation provided for people in the building.”

Building Regulations 2010, Schedule 1, Part F1(1)

The government’s Approved Document F turns that into numbers. For a bathroom, an extract fan is usually expected to move at least 15 litres per second. In a bathroom without an openable window, the fan should keep running for around 15 minutes after the light goes off. The door needs a gap of about 10 mm underneath so air can get in to replace what the fan takes out.

A window helps, but in January nobody opens it after a shower. Ducting matters too. A long run of flexible duct with several bends can cut a fan’s output badly, so it’s better to run it short and straight to the outside wall or the roof.

There’s a related rule in Part G4 that a room with a WC “must be separated from any kitchen or any area where food is prepared”. In practice a door does that. It comes up in small flats where the bathroom opens off the kitchen.

Electrics

Bathrooms are treated as a special location in the wiring regulations. The room is divided into zones around the bath and shower, and each zone limits what can go there and how well sealed it must be against water. All circuits in a bathroom need RCD protection.

Most electrical work in a room with a bath or shower is notifiable under Part P of the building regulations. That means it’s either done by an electrician registered with a competent person scheme, who certifies it and notifies building control, or it goes through building control directly. Keep the certificate. Solicitors ask for it when you sell.

Lighting is worth thinking about early, as cables have to go in before the boards and tiles. One ceiling light is rarely enough. A couple of downlights, a light at the mirror and something softer for the evening make a bigger difference than an expensive tap.

Materials and waterproofing

Plasterboard on its own is not suitable behind tiles in a shower. Cement board or a waterproof tile backer board is better, and the shower area should be tanked with a liquid membrane or sheet system, including the corners and around the valve and the waste. Most leaks in new bathrooms come from these junctions, not from the tiles.

Porcelain is the usual choice for floors and showers because it absorbs almost no water. There is more on that in choosing porcelain tiles. On a timber floor, large tiles need a stiff base, usually a ply overlay or backer board screwed at close centres, with flexible adhesive. A floor that moves cracks the grout within months.

Matt or textured tiles are safer underfoot in a wet room. Grout colour matters more than people expect, as pale grout on the floor shows dirt quickly. If you want a warm floor, electric underfloor heating is easy to add while the room is stripped, see everything you need to know about underfloor heating. The flooring under the bathroom is worth inspecting at the same time, as rot around old WCs is common.

Fittings

Before buying, check the practical things. Can the concealed cistern be reached for repairs through a removable panel or the flush plate? Does the shower valve have service isolators? Will the basin unit fit with the waste trap behind it, or does the drawer have to be cut? These details decide how easy long-term maintenance will be.

Order the long-lead items before the strip-out starts. Bespoke vanity units, shower screens made to measure and some imported tiles can take six to ten weeks.

Order of work

A typical sequence is:

• strip out and inspect the floor and walls;
• repair joists and lay a new deck if needed;
• first fix plumbing and electrics, with pipework pressure tested;
• boarding, tanking and screeding;
• tiling;
• second fix: sanitaryware, brassware, lights, fan, then silicone and decorating.

Tanking compounds and screeds need drying time before tiling, and tile adhesive and grout need time before the shower is used. Rushing this is a common cause of early failures.

Living through it

If it’s the only bathroom, plan for at least a week or two without a usable shower. Some people arrange a gym membership or stay with family. The WC can often be reconnected temporarily at night, but don’t count on it every day.

The water will be off at times. Old stopcocks in London houses often don’t close fully, so it’s worth checking yours before the job starts. In a flat, the communal stopcock may be in the basement or the street. Skips on the road need a licence from the council, and in many boroughs a parking bay suspension too, which can take a couple of weeks to arrange.

Common mistakes

Most problems come from a handful of things: fitting too much into a small room, an undersized extract fan, cheap boarding behind the shower, a WC moved where the joists don’t allow it, and products ordered after the job has started. Each one is easy to avoid if it’s thought about before the strip-out.

If you’re doing more than one room, the kitchens and bathrooms side of a refurbishment is usually planned together, because they share the same pipework, the same water supply and often the same stack.

FAQ

How long does a bathroom renovation usually take?

A full refit of a typical bathroom is usually two to four weeks on site. Moving the WC, building a wet room or repairing rotten joists adds time.

How much should I budget for a bathroom renovation in London?

As a rough guide, £10,000 to £20,000 for a mid-range full refit, and more for high-end finishes or major layout changes. Keep a contingency for what turns up under the floor.

Do I need to change the whole bathroom, or can I keep some of it?

If the layout works and the pipework and floor are sound, you can keep the positions and replace the finishes. If there’s water damage, a bouncy floor or old pipework, it’s better to strip it back.

Is it expensive to move plumbing in a bathroom?

Moving a basin or shower a short way usually isn’t. Moving the WC can be, because the 100 mm soil pipe needs a fall to the stack and the joists may not allow it.

What matters more: appearance or practicality?

A bathroom is used every day, so the layout, waterproofing and ventilation matter first. The finishes can be changed later; a leaking shower tray cannot be fixed without taking the tiles off.

Do I really need good ventilation if I can just open a window?

Yes. Building regulations require adequate ventilation, and in practice that means an extract fan of around 15 litres per second, with an overrun timer if there’s no openable window.

What are the most common mistakes people make with bathroom renovations?

Undersized extraction, cheap boarding behind the shower, moving the WC without checking the joists, and ordering products after the job has started.

Is a walk-in shower always better than a bath?

No. In a family home, especially the only bathroom, a bath is usually worth keeping. In an en-suite a walk-in shower often makes more sense.

Can a small bathroom still feel high-end?

Yes. Large-format tiles, a wall-hung WC and basin, good lighting and a recessed niche instead of shelves make a small room look more expensive than extra features do.

Why is planning so important before the work starts?

Once the room is stripped, every change costs more and takes longer. Decisions on layout, the shower, tiles and long-lead items are cheapest made beforehand.

Why choose Force Builders Ltd for a bathroom renovation in London?

Whoever you use, ask for the Part P electrical certificate, pressure-test results for the pipework and details of the tanking system used in the shower. Those are what decide how the bathroom holds up.

Force Builders Ltd is a London building company (Companies House 07049787) delivering house extensions, loft conversions and full refurbishments across Greater London. See our projects or get in touch.