A large tiled floor looks rigid, but the layers beneath it are not. The structure, the screed, the adhesive and the tiles all expand, contract and shrink at different rates. Without somewhere for that movement to go, stress builds up in the tiles. Movement joints give it that outlet. This guide is for FMs, retail managers and fit-out teams looking after large commercial tiled floors.
Why tiled floors move
- changes in temperature, including sunlight through glazing and underfloor heating
- moisture and drying shrinkage in screeds and concrete
- deflection of the structure under load
- movement at structural joints in the slab below
Each layer responds differently, and the tiles sit on top of all of them.
Large areas, long runs of glazing and floors laid over new screeds tend to see the most movement. Entrance areas often combine all three, which is why problems frequently show there first. Floors with heavy rolling loads, such as trolleys and cleaning machines, add stress to every joint.
Where movement joints usually go
The floor designer and the tiling specification set the positions. Typically, joints are placed:
- around the perimeter, where the floor meets walls, columns and upstands
- directly over structural movement joints in the slab
- where the substrate changes, for example from screed to timber
- at intervals across large areas
- at thresholds and changes in floor finish
Grout lines are not movement joints. They are rigid and can’t absorb movement.
What happens when joints are missing or failed
When the floor can’t move, stress builds. Tiles can crack, debond from the adhesive, or lift and tent upwards where two edges push together. Hollow-sounding tiles are often an early sign. Failed joint sealant also lets water and dirt into the joint, especially where floors are wet-cleaned. In busy public areas, lifted or cracked tiles become a trip hazard.
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Sealing a tiled floor joint
Floor movement joints are filled with a flexible sealant that can take foot traffic and cleaning. Depending on the floor and the specification, that may be a PU, silicone or hybrid product. BS EN 15651 Part 4 covers sealants for pedestrian walkways. A reseal starts with cutting out the old sealant, cleaning the joint back to sound, dry tile edges, fitting backing rod or bond-breaker where needed, and sealing and tooling flush or slightly concave. Colour can be matched to the grout or tile so the joints don’t stand out. See colour-matched sealant.
Practical points for occupied buildings
Floor joint work in shops, receptions and hotels is usually phased so areas stay open. Each section is closed while it is sealed and cures to the point stated for the product. Tell us your site hours and access windows and we’ll plan around them. If tiles have already lifted or cracked, they may need relaying by a tiler before joints are sealed; we’ll tell you if the edges need repairing first. Our floor joint sealing service covers retail and showroom floors.
Signs to watch for
- tiles that sound hollow when tapped
- cracks running in straight lines across several tiles
- tiles lifting at edges or along a line
- missing, split or dirty sealant in existing movement joints
- gaps opening at perimeters, thresholds and around columns
Report these early. A failed joint is far easier to put right than a run of debonded tiles. Our guide to why expansion joints fail explains the wider causes.
Quick answers
Can movement joints be added to an existing tiled floor?
Sometimes, by cutting new joints in the right places, but it needs advice from the floor designer or a tiling specialist. Positions must follow the movement in the floor and structure.
Why is my tiled floor cracking along a line?
A straight crack often follows a joint or crack in the slab beneath. If there is no movement joint above it, the tiles take the stress. A specialist should check the cause.
Does grout count as a movement joint?
No. Grout is rigid. Movement joints use a flexible sealant over a backing so they can open and close.
Related services
- Industrial and floor joint sealing
- Expansion and movement joint sealing
- Coloured and colour-matched sealant
More advice
- Warehouse Floor Joints: Stopping the Damage
- Why Expansion Joints Fail and How to Fix Them
- BS EN 15651 Sealant Classes in Plain English
- Colour-Matched Sealant on Commercial Jobs
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.