How to Tile a Floor

Laying floor tiles is one of the most impactful and durable improvements you can make to a kitchen, bathroom, utility room or hallway. Done correctly, a tiled floor will last 20–40 years with minimal maintenance. Done incorrectly, on a flexing subfloor, with the wrong adhesive, or without adequate expansion joints, tiles crack, de-bond and grout joints open within months. This guide covers everything from choosing the right tile type to finishing the grout, with particular attention to the standards and specification choices that matter in wet rooms, and to how they sit alongside the Building Regulations.

Tools and Materials

Before you start, assemble all tools and materials. Stopping mid-job to source items causes adhesive to skin over and layouts to go wrong.

Tools:

• Wet tile saw (or angle grinder with diamond blade for straight cuts)
• Notched trowel (notch size matched to tile, typically 6 mm for tiles up to 300×300 mm, 10–12 mm for large-format tiles)
• Rubber mallet or beating block and regular mallet
• Spirit level (1.2 m minimum) and laser level for large areas
• Tile spacers (typically 2–3 mm for floor tiles; 3–5 mm for natural stone)
• Tape measure, pencil, chalk line
• Mixing paddle and bucket (for adhesive and grout)
• Grout float, sponge, bucket of clean water
• Tile nibblers for curves and around pipes
• Knee pads

Materials:

• Floor tile adhesive: S1 or S2 flexible adhesive for most subfloors; rapid-set for time-critical jobs
• Grout: unsanded for joints under 3 mm, sanded for 3 mm and wider; epoxy grout for wet commercial areas
• Tile spacers
• Grout sealer (for natural stone and unglazed porcelain)
• Flexible sealant (silicone) for perimeter joints and internal angles
• Self-levelling compound if subfloor needs flattening
• Tile trim (aluminium or stainless) for exposed edges and doorways

Surface Preparation

This is the stage most DIYers underinvest in, and it is the single most common cause of tile failure.

Structural adequacy: A timber suspended floor must be rigid enough to carry tiles without flexing; a deflection limit of span/360 is commonly used, which for a 3 m span is about 8 mm. In practice, many suspended timber floors need overboarding before tiling. BAL, for example, suggests a tile backer board or 15 mm marine-grade plywood screwed down at 300 mm centres, with the screw heads flush.¹ Do not tile directly onto single-layer floorboards.

Flatness tolerance: The floor tiling code of practice is BS 5385-3:2024, which replaced the 2014 edition.² For tiles bedded in adhesive, the floor should reach surface regularity class SR1: no gap greater than 3 mm under a 2 m straightedge.³ High spots must be ground down; low spots filled with flexible floor leveller. This is a non-negotiable requirement, flexible adhesive cannot bridge hollows and will eventually crack under point loads.

Adhesion surface: Allow new work to dry before tiling: a sand and cement screed needs at least three weeks and a concrete slab at least six, and screeds should be moisture tested first.⁴ Prime all absorbent surfaces with an appropriate primer to prevent the substrate from drawing moisture out of the adhesive too quickly. Remove all dust, paint, grease and any previous tile adhesive residue.

Existing tiles: You can tile over existing tiles if they are sound, flat and firmly bonded. Grind the surface to key it, and use a flexible adhesive. Check the cumulative weight loading does not exceed the structural floor capacity.

Choosing Tile Size and Planning the Layout

Tile size: Large-format tiles (600×600 mm and above) create a contemporary feel and have fewer grout lines to clean, but they amplify any subfloor unevenness and require full-contact adhesive coverage with a back-buttered adhesive layer, both faces of the tile must be coated. Smaller tiles (300×300 mm or mosaic) are more forgiving of subfloor variation.

Layout planning: Never start from a wall. Find the centre of the room by snapping chalk lines between the midpoints of opposite walls. Check for square using the 3-4-5 method. Dry-lay a row of tiles in each direction from the centre point to check the cut sizes at the perimeter, you want a minimum half-tile width at all walls. Shift the layout if the cuts fall too narrow. Mark a working line and fix a straight batten at 90° to use as a guide for the first row.

Expansion joints: All tiled floors require movement joints at perimeters (between tiles and walls, skirting or fittings), minimum 6 mm wide, filled with flexible silicone sealant, never grouted. Large areas also need intermediate movement joints at the spacing the tiling specification sets. Grouting perimeter gaps is a common cause of tile cracking in domestic settings.

Tile Type Comparison

Porcelain is classed as group BIa, with water absorption of no more than 0.5%.⁶ As a price check, a 600 × 1200 mm porcelain floor tile was listed at £18.54/m² including VAT by a national builders’ merchant in September 2026.⁷⁸

Porcelain is the most practical choice for UK bathrooms and kitchens: it is frost-resistant, very hard-wearing and virtually non-porous, so glazed porcelain does not need sealing (some unglazed and polished porcelains benefit from a sealer). Ceramic is adequate for low-traffic dry areas and is more affordable. Natural stone requires regular sealing and is generally softer, making it more susceptible to etching from acidic cleaners.

Step-by-Step: Laying Floor Tiles

Step 1, Mix adhesive. Follow the manufacturer’s water-to-powder ratio precisely. The mix should hold a ridge without slumping. Let it slake for 5 minutes, then re-stir. Use within the open time stated on the bag (typically 30–60 minutes).

Step 2, Apply adhesive to the subfloor. Using the flat side of the notched trowel, spread a thin keying coat onto the subfloor. Then use the notched side to comb ridges at a consistent angle. Cover only 0.5–1 m² at a time to prevent skinning.

Step 3, Back-butter large-format tiles. For tiles over 600 mm in any dimension, also apply a thin coat of adhesive to the back of the tile and key it. This ensures full contact and eliminates voids that cause cracking under point loads.

Step 4, Lay the first tile. Place it firmly on the working line, twist slightly as you press down, then bed it with the rubber mallet or beating block. Check it is flat with the spirit level.

Step 5, Build out from the first tile. Work in sections, inserting spacers at each corner. Check level constantly, both within individual tiles and across multiple tiles. Adhesive squeeze-up into the spacer gaps is normal; excess can be removed with a pointed tool while still wet.

Step 6, Cut tiles for the perimeter. Measure each cut individually rather than assuming the walls are parallel. Mark and cut with the wet saw. Wear eye protection.

Step 7, Allow full cure. Do not walk on the tiles for at least 24 hours (rapid-set adhesives may allow foot traffic within a few hours; check the bag). Allow 48–72 hours before grouting with standard adhesives in cold conditions.

Grouting and Finishing

Step 8, Remove spacers and clean joints. Remove all tile spacers before grouting. Clean out any adhesive from the joints, grout needs to fill the full depth of the joint for durability.

Step 9, Mix grout. Follow the manufacturer’s ratio. Consistency should be smooth and spreadable without being watery. Pre-mixed grout in tubs is easier for small areas.

Step 10, Apply grout with the grout float. Work the grout diagonally across the joints, pressing firmly to fill them completely. Work in sections of 1–2 m². Remove excess grout from tile faces with the float held at a steep angle.

Step 11, Clean tiles. After 10–15 minutes (when the grout has firmed but not fully set), wipe the tile faces with a damp sponge. Rinse the sponge frequently. A light haze will remain; this can be polished off with a dry cloth once the grout is fully set (usually 24 hours).

Step 12, Seal perimeter joints. Apply flexible silicone sealant to all perimeter joints and internal angles. Smooth with a wet finger or sealant tool. This replaces grout in these locations, do not grout them.

Slip Resistance in Wet Areas

No Building Regulation sets a slip rating for a floor in a home, so what follows is specification rather than compliance. Two scales are quoted and they are not interchangeable. The pendulum test value (PTV) is the one HSE works to, where 36 or above is the low slip potential band.⁹ The R rating printed on tile data sheets comes from DIN 51130, a ramp walked in cleated safety boots, which HSE has reservations about because R10 alone spans a wide range of measured friction.⁹ As a rough specification guide only:

• R9, the bottom of the scale: HSE notes that the R scale runs from R9 to R13 and that R9 is slippery when wet⁹
• R10, common on domestic floor tiles, but HSE warns that some R10 surfaces are also slippery in wet or greasy conditions⁹
• R11, a sounder starting point for a shod floor that is often wet, such as a utility room
• R12 and R13, heavily contaminated environments

A tile’s R-value is a surface characteristic, not just a material characteristic, a polished marble floor may look superb but fall below R9, the lowest class, which makes it unsuitable for a bathroom floor. Always check the manufacturer’s R-value certificate before specifying for wet areas, and treat a wet barefoot area as its own case: R ratings are a shod test, so they say little about a shower floor underfoot.

Barefoot wet areas are classed A, B or C under a separate ramp test, DIN 51097, in which barefoot walkers test the floor with soapy water.⁹

Common Mistakes

• Not checking subfloor flatness. The SR1 tolerance of 3 mm under a 2 m straightedge is strict. Skipping this step is the leading cause of cracked tiles within the first year.
• Grouting the perimeter. All perimeter joints must be flexible silicone, not grout. Grout will crack as the structure moves seasonally.
• Using wall tile adhesive on floors. Wall adhesives are not rated for foot traffic loads. Always specify floor-grade adhesive.
• Under-notching the trowel. The notch depth determines adhesive coverage. Too small a notch leaves voids under the tile.
• Tiling over still-wet screed. Allow at least three weeks for a sand and cement screed and six for concrete, then check the moisture: a polythene sheet taped down overnight gives a rough test (condensation indicates excess moisture), and a hygrometer test is more reliable.

When to Call a Professional

• Suspended timber floors that deflect noticeably underfoot, a structural engineer’s assessment may be needed before tiling.
• Underfloor heating systems, tile adhesive and tile selection must be compatible with the UFH specification, and the system commissioning protocol must be followed before tiling.
• Large areas of natural stone, particularly marble, the stone is brittle and requires full adhesive contact; specialist installers typically achieve this more reliably.
• Wet-rooms with tanking membranes, the interface between the tanking and the tile adhesive is critical; improper sequencing causes leaks behind tiles.

Cost Summary

For a standard kitchen or hallway in the UK, expect total installed costs of about £50–£105/m² using ceramic or mid-range porcelain, including all materials and professional fitting. Natural stone installed by a specialist typically runs £80–£180/m² all-in.

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.