Cracked tiles and blown grout joints are one of the most common tiling complaints in New Zealand homes — and a lack of proper movement joints is usually the culprit. Tiles and the substrates beneath them expand and contract at different rates due to temperature changes, moisture, and structural movement. Without somewhere for that movement to go, something has to give, and it's almost always the tile or grout that loses. Understanding where movement joints are needed, and how to install them correctly, can save you a costly retile down the track.
Why Movement Joints Matter
Tiles are rigid and bond tightly to their substrate. When the building moves — even slightly — stresses build up across the tiled surface. Movement joints (also called expansion joints or soft joints) are deliberately left ungrouted and filled with a flexible sealant, giving the assembly somewhere to breathe. BRANZ research consistently identifies missing or inadequate movement joints as a leading cause of tile failure in NZ buildings.
What the Standards Say
In New Zealand, tiling work is guided by NZS 4243 and the tile industry generally follows ISO 13007 for adhesives and grouts, along with manufacturer specifications. The MBIE Building Performance guidance and the NZ Building Code also set expectations around durability and weathertightness that movement joints directly support. While there is no single prescriptive NZ standard that covers every tiling scenario, the widely accepted industry benchmark — used by most professional tilers here — is based on the Tile Council of North America (TCNA) Handbook and European standard BS EN 14411, which recommend movement joints at specific intervals.
Where Movement Joints Are Required
As a general rule, movement joints should be placed:
- At all changes of plane — where a floor meets a wall, a step riser meets a tread, or a floor meets a different floor material
- At all structural joints — wherever there is a control joint, construction joint, or expansion joint in the concrete slab or substrate beneath
- Around the perimeter of every tiled floor area, between the tiles and any fixed element (walls, columns, cabinetry, door frames)
- Across large field areas — in the field of the tile, at regular intervals
- Where different substrates meet — for example, where a concrete slab meets a timber framed floor
- In heated floors — underfloor heating causes significant thermal movement and requires more frequent joints
Spacing in the Field
For interior floors, the general industry guideline is to install field movement joints at intervals of no more than 4–5 metres in each direction. In areas exposed to direct sunlight, temperature extremes, or underfloor heating, reduce this to around 2.5–3 metres. Outdoors or in unheated spaces like garages, joints should be even closer together.
Here's a quick reference:
| Location | Recommended Maximum Spacing |
|---|---|
| Interior, climate-controlled | ~4–5 m each direction |
| Underfloor heating | ~2.5–3 m each direction |
| Exterior / unheated | ~2–3 m each direction |
| Perimeter (all areas) | Always required |
| At substrate changes | Always required |
These are general guidelines. Always follow your tile and adhesive manufacturer's specifications, which may be more conservative.
How Wide Should Movement Joints Be?
Perimeter and field movement joints are typically 6–10 mm wide for most residential floors. Larger format tiles (600 mm and above) and exterior applications generally need wider joints. The joint must be deep enough to allow the sealant to flex properly — a depth-to-width ratio of roughly 1:1 is ideal, and a foam backer rod is used to control depth before sealant is applied.
Choosing the Right Sealant
Movement joints must be filled with a flexible, paintable silicone or polyurethane sealant — never standard grout, which is rigid and will crack. Many tilers use colour-matched silicone so the joint blends with the surrounding grout. Sika and Ardex both offer sealant products suitable for tiled movement joints, and Mapei produces colour-coordinated silicone ranges designed to match their grout lines.
When selecting a sealant:
- Choose mould-resistant formulas for wet areas (bathrooms, laundries)
- Ensure it is rated for foot traffic if used on floors
- Match the colour to your grout as closely as possible
- Allow full cure time before use — check the product datasheet
Wet Areas and the NZ Building Code
In wet areas such as bathrooms and laundries, movement joints are especially critical. The NZ Building Code Clause E3 (Internal Moisture) requires that wet area linings prevent moisture penetration. A cracked grout line caused by missing movement joints can allow water behind tiles, leading to substrate damage, mould, and costly repairs. Always install a perimeter movement joint where floor tiles meet wall tiles or the base of a shower wall.
DIY or Professional?
Planning and installing movement joints correctly requires an understanding of the substrate, tile format, and site conditions. While a competent DIYer can install a perimeter silicone joint in a straightforward situation, field movement joints in large or complex areas are best left to a professional tiler who can assess the specific risks. Tiling over underfloor heating, large-format tiles, or structural slabs with existing control joints are all situations where professional advice is strongly recommended.
Tiling itself is not licensed restricted work in the same way as electrical or plumbing, but poor workmanship can void warranties and cause building code compliance issues. If your project involves plumbing penetrations, waterproofing membranes, or alterations to drainage, those elements must be carried out by a licensed tradesperson registered with the Plumbers Gasfitters & Drainlayers Board.
When to Call a Professional
Consider hiring a qualified tiler if:
- Your floor area is larger than a small bathroom
- You are tiling over underfloor heating
- Large-format tiles (600 mm+) are being used
- The substrate is a structural concrete slab with existing control joints
- You are unsure where movement joints should go
- Existing tiles have cracked and you need to diagnose the cause before retiling
A skilled local tiler will assess your specific substrate, tile selection, and conditions to design a movement joint layout that meets both manufacturer requirements and NZ Building Code expectations. You can find qualified tilers in your area at tradedirectory.co.nz.
Sources & Further Reading
- BRANZ – Build Magazine and technical resources
- MBIE Building Performance – NZ Building Code guidance
- Ardex NZ – tile adhesives and movement joint products
- Mapei NZ – grouts, sealants and tiling systems
- Sika NZ – construction sealants and adhesives
- WorkSafe NZ – safe work practices on construction sites