Bathroom tiling looks like a weekend job and mostly is, but the parts that decide whether it lasts are the ones you cannot see once the grout is in: a sound, flat, dry surface, sensible waterproofing in the shower area, the right adhesive, and a ventilation system that stops the room running with condensation. This guide goes through those in the order you will meet them, with a worked example of tile, adhesive and grout quantities and a note on the regulations that touch a bathroom refit.

What the regulations say about bathroom work

Tiling itself needs no approval. A bathroom refit, however, can involve work that does. The Planning Portal states that planning permission is generally not needed for kitchen or bathroom installation unless the work forms part of an extension, but building regulations may still apply to the plumbing, drainage, electrics and ventilation. In England the relevant documents are published by GOV.UK: Approved Document F covers ventilation, Approved Document G covers hot water safety and sanitation, Approved Document H covers drainage, and Approved Document P covers electrical safety.

  • Ventilation. If you are replacing an extractor fan or adding a bathroom where there was none, the fan should meet the airflow requirement in Approved Document F. The figure commonly quoted for an intermittent extract fan in a bathroom is 15 litres per second; check the current table in the document, as ventilation guidance has been updated in recent years.
  • Electrics. The areas around baths and showers are treated as special locations in the wiring rules (BS 7671), with limits on where sockets, switches and light fittings may go and what protection rating they need. Adding a new circuit is notifiable work in England; like-for-like replacement and small additions have different rules. Use a registered electrician for anything beyond a simple swap, and see our guide on Part P electrical work for the details.
  • Plumbing and drainage. Moving a waste pipe or soil stack can bring drainage requirements into play, so ask building control before you reroute anything.

These references are for England. Wales, Scotland and Northern Ireland have their own building regulations or standards, so check locally if you live there.

Prepare the wall properly

Adhesive can only be as good as the surface under it. Check these before you buy a tile:

  • Flatness. Hold a straightedge against the wall. Large tiles show every ripple. Plaster humps can be ground or skimmed back; hollows can be filled with a levelling compound or the thickness of adhesive adjusted, but beyond a few millimetres, it is better to re-board or re-plaster.
  • Soundness. Tap for hollow areas, scrape for powdery or flaking surfaces and remove loose paint, wallpaper and old adhesive. Old tiles can sometimes be tiled over if they are well bonded and the surface is keyed, but the extra weight and thickness need considering.
  • Dryness. Fix any leaks and let damp walls dry completely first. Fresh plaster typically needs several weeks to dry, depending on thickness and conditions, and manufacturers of tile adhesive specify a minimum drying time before tiling.
  • Substrate type. Standard plasterboard is acceptable for tiling in dry areas, but in wet areas it needs to be primed or replaced with a moisture-resistant tile backer board. Cement-based backer boards and foam-core tile boards are widely used behind showers, because they do not swell or soften when wet.

Prime absorbent surfaces with the primer recommended by the adhesive manufacturer. Priming prevents the wall sucking moisture out of the adhesive too fast.

Waterproofing: tanking the shower and bath areas

Ceramic tile and grout are not waterproof; grout is porous and water can pass behind it. In a shower enclosure, or any area that gets sustained direct water, a waterproof membrane or tanking system under the tiles is strongly advisable. Options include liquid-applied membranes brushed or rolled on, with reinforcing tape in corners and around fittings, and tile backer boards with sealed joints. Follow the manufacturer's system as a whole: board, tape, sealant and adhesive from the same range are tested together.

Around a bath, the area above the bath edge gets splashes rather than sustained spray, so a primed surface and a flexible sealant at the bath junction is the minimum. Use silicone sanitary sealant, not grout, in the corner between the bath or shower tray and the tiles and at internal corners, because the joint moves. Fit the bath and fill it with water before sealing, so that the joint is at its widest when you seal it. Otherwise it will tear open when the bath is used.

Choose tiles and adhesive

For walls, ceramic tiles are standard. Porcelain, natural stone and glass are options but behave differently: porcelain is dense and needs a high-quality flexible adhesive, natural stone may need sealing, and glass tiles need white adhesive and a smooth substrate.

Adhesive comes as ready-mixed paste and as cement-based powder. Ready-mixed paste is convenient for small areas of standard ceramic tile on a sound dry wall; it is not generally the right choice for areas of heavy water exposure, large-format tiles or heavy tiles. Cement-based adhesives, mixed with water, are the usual choice for showers and for large or heavy tiles, and many are classed under the standard BS EN 12004. Look for products marked as suitable for wet areas and for the tile type you are using, and read the data sheet for open time, notch size and coverage.

Setting out: where to start

  1. Measure the wall and find the centre of the focal point, such as the bath or basin.
  2. Dry-lay a row of tiles along the floor or a batten, with spacers, to see where cuts fall. You want symmetrical cuts at both ends of a wall, not a thin sliver of tile at one end.
  3. Fix a level batten a tile height (plus a grout joint) above the bath or floor, because floors and bath tops are rarely level. Start the first full row from this line. The cut row goes at the bottom, hidden by the bath or skirting.
  4. Mark a plumb vertical line from the centre or from the point you chose, and check it with a level, not by eye.

Estimating tiles, adhesive and grout

Measure each wall area in square metres, subtract large openings such as the window and the door, and add an allowance for cuts and breakage: 10 percent for straight lay, 15 percent for diagonal or patterned layouts.

Worked example (illustrative numbers): tiling above a bath, with the long wall 1.7 m wide and two end walls 0.7 m wide, all tiled to 1.2 m high, using 300 x 200 mm ceramic tiles, 8 mm thick, with 3 mm joints.

  • Area = (1.7 x 1.2) + (2 x 0.7 x 1.2) = 2.04 + 1.68 = 3.72 square metres.
  • Tile area = 0.3 x 0.2 = 0.06 square metres, so 3.72 / 0.06 = 62 tiles. Add 10 percent: 62 x 1.10 = 68 tiles; round up to a full box.
  • Adhesive: coverage depends on trowel notch size and wall flatness, so use the data sheet. As an assumption for this example, 3 kg per square metre gives 3.72 x 3 = 11.2 kg, so one 15 kg tub or bag.
  • Grout: a standard approximation is (tile length + tile width) / (tile length x tile width) x tile thickness x joint width, which gives litres per square metre when everything is in millimetres. Here (300 + 200) / (300 x 200) x 8 x 3 = 0.2 litres per square metre. At an assumed grout density of 1.6 kg per litre, that is about 0.32 kg per square metre, so 3.72 x 0.32 = 1.2 kg. A 2.5 kg bag is ample, and covers a little extra for wastage.

The wall tile, grout and adhesive estimator automates these figures for different tile sizes and joints. If the walls themselves need building or boarding first, the drywall and stud wall calculator covers the boards.

Fixing the tiles

  1. Spread adhesive on an area you can tile before it skins over, usually about a square metre at a time. Comb it with a notched trowel held at a consistent angle so that the ridges run in one direction.
  2. Press each tile with a slight twisting motion, then check that the adhesive makes full contact. Lift a tile occasionally to check the back is covered.
  3. Use spacers at corners. Check the face with a level every few rows and wipe adhesive from the face immediately.
  4. Leave expansion gaps at internal corners and against fixtures, to be filled with sealant, rather than rigid grout.
  5. Cut tiles with a manual cutter for straight cuts and a wet saw or tile nibbler for curves and holes. Wear eye protection, since ceramic chips fly, and use dust protection when cutting porcelain with a wet or dry saw.

Leave the adhesive to cure for the time the manufacturer specifies, commonly around 24 hours for standard cement-based products, before grouting. Rapid-set products are faster.

Grouting and sealing

Choose a grout classed for wet areas; a water-resistant or epoxy grout is popular in showers. Push it firmly into the joints with a rubber float held diagonally across the tiles, then clean the surface with a damp sponge, rinsing frequently. Polish the haze off with a dry cloth after it dries. Do not use a lot of water, since it weakens the grout and can wash out the colour. Seal the corners and the perimeter with silicone sealant after the grout has fully cured, and do not use the shower for the time recommended by the manufacturer, often 24 to 72 hours or more.

Keep the room dry

A fan that runs only while someone is in the room often leaves humid air behind. A fan with a humidistat or a run-on timer clears moisture for longer. An extractor that is too small or ducted poorly can leave the walls running with condensation, which mould loves. If mould is already a problem, tackle the cause, not just the stain.

When to get help

Employ a professional tiler or builder for a wet room, where the entire floor and walls form one waterproofed enclosure, for any job that involves rerouting plumbing or drainage, and for substantial damp problems. A registered electrician should handle bathroom wiring. This is general information, not professional advice; building control or the manufacturer's technical helpline can clarify your specific case.

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