Tile floor installation, which is really a substrate job

What is tile floor installation?

Tile floor installation is the setting of ceramic, porcelain or stone tile into mortar over a substrate stiff enough not to move under it, followed by grouting and sealing. The tile itself is the easy part. What decides whether the floor lasts is underneath: how much the floor structure deflects, what the tile is bonded to, and whether the installation has somewhere to move at the perimeter and across large spans.

Signs you need tile floor installation

• You need a genuinely waterproof-capable floor for a bathroom, mudroom or laundry
• The existing tile is cracked, hollow-sounding or lifting and has reached the end of its life
• You want a floor that tolerates standing water, salt, grit and pet claws indefinitely
• You are installing radiant floor heating and want the material that transfers it best
• Grout is failing in lines across the room rather than in isolated spots
• The room is an entry or a kitchen where the floor takes abuse that wood or vinyl would show

Seeing something not on this list? Browse flooring problems by symptom →

How tile floor installation actually works

1. 1

   Assessing deflection in the floor structure

   Before any material is chosen, a competent setter considers how much the floor flexes - joist size, span, spacing and subfloor thickness. Tile and grout have almost no tolerance for movement, and stone has less than ceramic.

   Watch forNobody mentioning the joists at all. On an upper floor or over a long span, a floor that feels bouncy underfoot will crack tile regardless of how well the tiling itself is done. Stiffening the structure is part of the job, or the job should not happen.

2. 2

   Building the substrate

   Over a wood subfloor this usually means a second layer of plywood plus cement backer board bedded in mortar and fastened, or an uncoupling membrane bonded down. Over concrete it may be direct bonding, or a membrane over cracks.

   Watch forBacker board screwed down dry with no mortar bed under it. The mortar is not glue - it fills voids so the board is fully supported. Skipping it leaves the board free to flex over every gap.

3. 3

   Crack isolation and waterproofing where needed

   An uncoupling or crack-isolation membrane lets the substrate move slightly without transmitting that movement into the tile. In wet areas the waterproofing layer is a separate decision and goes where water actually is.

   Watch forWaterproofing assumed to come from the tile. Porcelain absorbs almost nothing, but grout joints are not a waterproof plane. In a wet room, the membrane is the waterproofing and the tile is the wear surface.

4. 4

   Dry layout and setting out

   The setter finds the room's centre lines, dry-lays to check where cuts fall, and adjusts so the sightline from the door reads well and no edge ends in a sliver. Pattern choice happens here, and it changes waste and labour.

   Watch forLayout started from a wall rather than from centre lines. It produces tapered cuts along the most visible edge, and there is no fixing it after the mortar sets.

5. 5

   Setting in mortar with full coverage

   Thinset is combed with a notched trowel sized to the tile, and tiles are set and beaten in so the ridges collapse into full contact. Large tiles typically need mortar back-buttered as well. Coverage is checked by pulling a set tile occasionally.

   Watch forCorners of tiles sounding hollow when tapped. Voids under a tile are where cracks start, and on a large-format tile a partial bond is a guaranteed failure at the unsupported corner.

6. 6

   Movement joints

   Soft, flexible joints go at the perimeter of the room and at intervals across large fields, plus wherever the tile changes plane or meets a different material. They are filled with sealant, not grout.

   Watch forGrout run tight to the wall all the way around. Tile expands; the house expands differently. With nowhere to move, the pressure releases as a tented row or cracked grout, usually in the second year.

7. 7

   Grouting and sealing

   Grout is chosen for joint width and the tile type, worked into joints, and cleaned off before it sets. Cementitious grout is usually sealed; some modern grouts do not need it. Natural stone often needs sealing before grouting to stop staining.

   Watch forStone grouted without a pre-seal. Grout pigment wicks into porous stone and will not come out. Ask specifically whether your material needs sealing before grout goes anywhere near it.

8. 8

   Cure before use

   Mortar and grout both need cure time before traffic and before sealer. Rushing it means walking on tiles that have not fully bonded and dragging the grout out of joints.

   Watch forA schedule with no gap between grouting and putting the room back in service. Cure time is not padding.

What does tile floor installation cost?

Tile is usually the most labour-intensive floor to install, and substrate work - backer board, membranes, structural stiffening - can rival the tiling itself. Large-format and natural stone cost more to set than standard ceramic. The Cost Guide breaks the ranges out by tile type.

See the full tile floor installation cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →