1. Plan your bathroom

A good starting point is to draw up a scale floorplan for your proposed bathroom. If you have a particular design in mind, estimate the space required and make sure you have a similar area. If you don’t, you will need to either look for a new location or compromise on your chosen design.

When choosing a location for your bathroom, although it’s always preferable to have a window to provide natural light, it’s not essential. If you have no windows make sure you can duct an extractor fan to the outside. Access to the sewer should also be a consideration – the easiest and most cost-effective option is to make use of an existing soil and vent pipe.

Equipped with a floorplan, either on paper or on a computer, you can try out different layout options using scale cut-outs or graphics. You will find that any sanitaryware you choose will have a plan showing dimensions in the specification that you can download and then use in your layout. Several leading manufacturers also offer free design tools.


Related articles: 10 tips for installing bathroom plumbing | Planning and costing your bathroom renovation | 7 bathrooms for spa lovers


5. How much will a new bathroom cost?

Updating an existing bathroom without altering the plumbing layout will cost:

  • £1,500-£2,500 for a basic specification
  • £2,500-£5,000 for a good specification
  • £5,000-£15,000 for an excellent specification

Building a new bathroom in an extension, conversion or remodel
will involve additional costs for the structure and to bring in services:

  • £3,000-£4,000 on top of the construction for a basic specification
  • £4,000-£6,500 for a good specification
  • £6,500-£16,500 for an excellent specification

Building a new shower room formed in an extension, conversion or remodel will cost:

  • £2,500-£3,500 for a basic specification on top of the building work
  • £4,500-£5,000 for a good specification
  • £5,000-£10,000 for an excellent specification

2. Consider a bathroom designer

If you are not confident about designing your own bathroom layout, you could approach an interior designer to help, or visit a bathroom showroom that offers a design service. There are also lots of design-and-build companies, which will offer a design service as part of a contract to install a whole new bathroom

bathroom with white walls and features and antique furnitureThis bathroom in a listed home has been decorated with vintage finds and kitted out with period-style santiaryware


3. Building regulations for bathrooms

Several building regulations apply to bathrooms, mostly in relation to safety, hygiene, ventilation and electrical safety, including lighting. You also need to ensure there is adequate water pressure for all the fittings and a sufficient hot water flow rate – a plumber can advise on this.

You may need to:

  • upgrade your boiler
  • add a larger hot water cylinder
  • change to an unvented mains pressure system
  • add pressure pumps
  • install a new independent water heater
  • upgrade the incoming mains supply

Make sure you budget for this.


4. Decide on quality

The cost of adding a new bathroom will vary according to the amount of work required to form walls, upgrade the floor and make alterations to services, such as plumbing and electrics. The most significant variable, however, will be the quality of the fixtures and fittings.

In the estimates below, basic quality assumes:

  • off-the-shelf white sanitaryware
  • taps from a builder’s merchant or DIY shed
  • basic-range ceramic tiles around the bath and basin
  • vinyl flooring
  • an extractor fan
  • a fixed central light fitting
  • a radiator

Good quality assumes:

  • mid-range brand sanitaryware and taps
  • branded tiles around the bath and basin
  • task and ambient lighting
  • a heated towel rail
  • radiator or underfloor heating

Excellent quality assumes:

  • designer-range sanitaryware and taps
  • tiled floors and walls
  • stone vanity tops and bath surround
  • a heated towel rail and underfloor heating
  • task, ambient and mood lighting.

Prices will usually be subject to VAT at 20 per cent.


bathroom in a basement with wooden vanity unit and wooden mirror and walk-in showerA problematic layout was overcome in this basement bathroom


6. Choose the right heating

Underfloor heating is ideal for a bathroom, especially where space is tight. You can extend an existing radiator system to add an underfloor heating circuit, with the pipes laid between the timber joists, and insulation beneath.

Electric underfloor heating mats are easier to install as they do not increase the floor level significantly. They are inexpensive to buy, but will cost more to run than a water-based system. In a large bathroom, you may need additional heating, such as a radiator or heated towel rail.


7. Think about bathroom lighting

Plenty of good lighting is essential in a bathroom so that it feels bright and hygienic. As well as strong ambient lighting, you should think about adding task lighting for mirrors and mood lighting for atmosphere.

Recessed spotlights are a great choice for ambient lighting in a contemporary bathroom, with discreet floor- or wall-mounted washes. Baffled lights behind mirrors or under units can be added for atmosphere. LED lights are ideal for bathrooms.

Fixed ceiling light fittings are best for a traditional-style bathroom, with wall washes and sconces to add atmosphere. For a more opulent look you could consider including a decorative chandelier, too.

All electrics, including the light fittings, must be compliant with the building regulations Part P and be suitable for use in a damp environment. Each circuit should be controlled independently, ideally with dimmer switches, so you can adjust the mood for relaxation in the evening or a brisk shower in the morning.

Sensor lights are a new innovation that means you don’t have to click a switch when using the bathroom in the middle of the night.


8. Adding an en suite bathroom

A new shower room can be created in a space only 90x260cm (2.34 square metres), with a shower at one end, the WC at the other and the basin in the middle. For the best shower experience, make sure you have good pressure on both hot and cold water feeds.

Off-the-shelf cubicles and pre-formed trays are the most cost-effective option, and are the simplest to fit. For a contemporary look, go for a low-profile or wetroom-style shower tray, where the whole floor is waterproofed and tanked, with the water draining through a waste hole or slot in the floor.

Pre-formed walk-in trays, ready for tiling, are widely available (try Impey, WEDI, Marmox or Bette) to suit timber or concrete floor structures. To avoid leaks, it is vital you follow any waterproofing instructions to the letter.

To maintain a constant water temperature and avoid any cold-water shocks, thermostatic shower mixer valves are worth the extra cost.

vintage style bathroom with plinth under freestanding bathLuxurious freestanding sanitaryware has added a traditional touch to this stylish bathroom


9. Converting a spare room into a bathroom

  • It is possible to branch off new pipework from existing hot and cold plumbing runs or to add a new run from the cylinder or boiler. At only 10-15mm diameter, plumbing runs are normally easy to conceal within the floor or ceiling voids by cutting a channel in a wall and plastering over it, or by ‘boxing in’ around it.
  • If the distance from the hot water cylinder is considerable, the time spent waiting for the hot tap to run hot may not be practical for daily use, in which case, a good solution is to loop the hot supply back to the cylinder and add a circulating bronze pump with programmable time clock. You can then have instant hot water whenever it’s required simply by setting the time clock.
  • Try to site the WC where it can easily be connected to an existing internal or external soil stack; do so using a Y-junction. If this is not possible, add a new soil pipe (diameter 110mm), and bring it out on the same side of the house as the existing drains, connected via a new inspection chamber at a depth that provides a sufficient fall into the sewer.
  • Basin and bath wastes – pipes with a diameter of 40-50mm – can both be connected to the soil pipe and boxed in to conceal them. If there is no soil pipe, install a pumped macerator system with a flexible small-bore waste pipe.
  • All electrics need to comply with building regulations Part P, which requires light fittings and sockets to be a safe distance from wet areas, which are zoned from 0 to 2 according to the risk of electric shock.
  • Fit rapid ventilation to meet with building regulations Part F. This is typically an extractor fan mounted on the wall or ceiling.

10. How to extend your bathroom

  • Draw up a floorplan for the new bathroom space and start with a blank canvas – making sure that it is in the right location relative to bedrooms. If not, now is the time to move it.
  • Finding finishes that match existing designs is usually a waste of time; it is better to gut the space and start afresh.
  • Salvage any good-quality taps or sanitaryware, such as a classic roll-top bath, or, for a cost-effective way to update existing fittings, you can always re-enamel or add a new surround to a bath.
  • Design the new layout to make the best possible use of the space, then alter the wiring, plumbing, ventilation and lighting to suit.
  • It will usually be easier and cheaper to refit the WC in the same position, unless you are adding new soil pipework.
  • Upgrade your heating to suit the larger space and ensure there is sufficient pressure for mixer taps and showers.
  • If fully tiling the space, new and old walls can be clad in tile board (try Aquapanel or WEDI), and therefore will not need to be plastered.
  • Conceal services in the walls for a neat, contemporary design.

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