Floor-to-Wall Movement Joints: Schlüter Profiles, Silicone in Internal Angles and Joint Frequency

Summary

Movement joints are among the most misunderstood and most frequently omitted requirements in tiling. Most tile failures over 5–10 years are directly attributable to insufficient movement joints — tiles debond, grout cracks, and in worst cases tiles lift off the floor entirely. The root cause is always the same: differential movement between the tile layer and the substrate, accumulated at a rigid grout joint that cannot accommodate it.

The tile assembly (adhesive + tile + grout) is a rigid, high-modulus layer bonded to a substrate that moves differently. As the building structure deflects under load, as the concrete or screed undergoes drying shrinkage, as thermal cycles cause expansion and contraction, the rigid tile layer must either accommodate the movement through designated joints or transmit it as stress through the weakest link — usually the adhesive bond or the tile itself.

BS 5385 Parts 1 and 3 are the British Standards governing wall and floor tiling respectively. Both documents contain explicit requirements for movement joint provision. These are not optional guidance — they are the minimum standard of workmanship for a compliant tile installation, and omitting them can affect professional indemnity insurance claims where tile failures are disputed.

Key Facts

• BS 5385-1 — British Standard for wall tiling; requires silicone in all internal angles
• BS 5385-3 — British Standard for floor tiling; specifies movement joint frequency by tile size and substrate type
• Internal angles — ALL internal angles (floor/wall and wall/wall) must be filled with silicone, not grout; this is one of the most frequently breached rules in residential tiling
• 3m movement joint frequency — for floor tiles ≤600mm, movement joints at maximum 3m centres in each direction
• 4.5m frequency — for floor tiles ≤300mm in heated buildings; can extend to 4.5m centres
• Structural movement joint — wherever a building structural movement joint exists (expansion joint in slab, junction between two different structures), a corresponding movement joint must exist in the tile finish
• Silicone joint width — minimum 6mm width for floor movement joints; 5mm for wall joints; never less than 2mm
• Schlüter-JOLLY — aluminium or stainless steel angle bead for external corners on wall tiles; available in anodised aluminium and brushed stainless
• Schlüter-DILEX-EKE — coved floor/wall transition profile; combines a movement joint function with a hygienic coved detail (no internal grout angle)
• Schlüter-DILEX-KSNS — expansion joint profile for mid-floor movement joints; surface-mounted, compressible centre section
• Schlüter-RENO — transition profile between different floor heights at doorways
• Joint width calculation — minimum joint width = tile length ÷ 300; absolute minimum 2mm for wall tiles; 6mm for floor joints
• Sanded vs unsanded grout — joints under 3mm: unsanded; 3–6mm: sanded; over 6mm: wide-joint grout or medium-bed mortar; epoxy grout for joints 1–6mm in wet areas
• Never tile over tile — if removing existing tiles exposes a sound adhesive key, feather-edge levelling compound and prime before retiling

Quick Reference Table

Detailed Guidance

Why Internal Angles Cannot Be Grouted

The floor/wall junction is the single most critical movement joint in any tiled room. Here is why:

1. The floor slab and the wall are different structural elements that move independently. The floor deflects under load; the wall moves with the building structure.
2. The floor screed and wall plaster/board also move differently — screed undergoes drying shrinkage (typically 0.5–1.0mm/m); plasterboard expands and contracts with humidity.
3. At the internal angle, these two independent movements meet. If the joint is filled with rigid grout, the accumulated stress at the corner will eventually crack the grout, debond the adjacent tiles, or both.

BS 5385-3 Clause 6.1 states clearly: "Movement joints should be provided at perimeter of tiled areas and at all internal angles, aligned with the existing substrate joints." Filling this joint with silicone allows the 5–10mm of silicone to accommodate the differential movement without transmitting stress to the tile body.

The correct process is:

1. Tape the internal angle with a strip of release tape before tiling to prevent adhesive from bridging the joint
2. Lay tiles to within 5–10mm of the wall (floor tiles) or to within 5–8mm of the floor (wall tiles) — never butt tiles against each other in the corner
3. After grouting is complete and the grout has cured, remove the tape, clean the joint, and apply silicone in a single pass with a caulking gun
4. Smooth the silicone with a wet finger or a silicone tool to a slightly concave profile
5. Do not paint or apply grout over the silicone

Schlüter Profile System

Schlüter-Sistemas manufactures a comprehensive range of profiles that solve movement joint, edge protection, and transition problems with a factory-finished product. These profiles are specified in architects' drawings and are the industry standard for quality commercial and residential tiling.

Schlüter-JOLLY (external corner profile) Used to protect and finish the exposed edge of wall tiles at external corners. The tile slides into the leg of the profile; the raised face of the profile caps the tile edge. Available in polished chrome, brushed stainless, matte gold, and anodised aluminium to match bathroom fittings. Installed during tiling: the profile is bedded in adhesive, the tile butts against it, and the tile face aligns flush with the profile face.

Schlüter-DILEX-EKE (floor/wall transition) A coved transition profile that installs at the floor/wall internal angle. It provides a hygienic coved profile (no tight internal angle to collect dirt) and incorporates a compressible rubber or PE core that functions as the movement joint. The tile on the floor and the tile on the wall both bond to the wings of the profile rather than meeting at a sharp angle. Essential in commercial kitchens, food preparation areas, and healthcare facilities.

Schlüter-DILEX-KSNS (mid-floor expansion joint) A surface-mounted expansion joint profile for floor tiles. The profile has two flanges that bond into the adhesive bed; the centre section is a compressible silicone or EPDM element that allows lateral movement. Installed by cutting the tile layout to accommodate the profile at the planned joint location, setting the profile in the adhesive, and then continuing to tile from the profile outwards.

Schlüter-RENO (level transition) Profiles for transitioning between two floor surfaces at different heights, particularly at doorways. Available in straight (RENO-T) and stepped profiles (RENO-TK) with height compensation from 4mm to 25mm.

Schlüter-KERDI-BAND and KERDI-FLEX Waterproofing seam tape used with the Schlüter Kerdi-System waterproofing membrane. KERDI-BAND is applied over all joints and corners in the waterproofing layer before tiling. KERDI-FLEX is a flexible strip for movement joints within the waterproofing layer.

Movement Joint Frequency by Tile Size

BS 5385-3 Section 6.1 gives the following guidance on movement joint frequency for floor tiles:

Tiles ≤600mm (longest face):

• Maximum 3m between movement joints in each direction
• This applies in both directions — a 5m × 5m room needs a movement joint at 3m in both the x and y direction

Tiles ≤300mm:

• In heated buildings (underfloor heating, warm environments), can extend to 4.5m maximum
• In unheated environments or external use: 3m maximum

Large format tiles (>600mm):

• More frequent movement joints required; consult the tile manufacturer and adhesive manufacturer
• Very large format tiles (>1200mm) require an engineer's specification for joint provision

Underfloor heating:

• The UFH system introduces significant thermal cycling into the floor structure
• Movement joints must be installed at the perimeter of every UFH zone, in addition to the general frequency requirements
• Screed must be fully cured and the UFH commissioning cycle completed before tiling

Tile Over Tile: When Is It Acceptable?

Tiling over an existing tiled floor or wall is possible in limited circumstances, but carries risks that must be assessed before proceeding:

When it may be acceptable:

• The existing tiles are firmly bonded (tap test — no hollow sound)
• The substrate can carry the additional weight (≤32kg/m² for wall tiles)
• The tile adhesive system includes a primer and bonding agent suitable for non-porous existing tiles
• The increased floor height can be accommodated at door thresholds

When existing tiles must be removed:

• Any hollow or debonded areas — tiling over these will extend the debonded area
• The adhesive bond of the existing tile is doubtful (e.g., tiles installed with a spot-fixing method; wide hollow voids)
• The existing grout is loose, cracked, or contaminated with mould that penetrates the joint depth
• The existing tile surface is heavily textured, sealed with silicone contamination, or otherwise unable to provide mechanical key

If retiling over existing tiles, apply a tile-on-tile adhesive bonding primer (BAL Bond SBR, Mapei Primer G or equivalent), allow to dry, then apply a standard C2 S2 adhesive in a notched bed. Feather-edge levelling compound may be needed to flatten any lippage before the new tiles go down.

Grout Selection by Joint Width

Grout colour matching for repairs: always test the grout colour on a spare tile or in a hidden corner before committing to a large area. Grout colour changes slightly as it dries. Wet grout typically appears 1–2 shades darker than the final dry colour. Pigmented grout sealers can be used to modify an existing grout colour — test first.

Frequently Asked Questions

My client wants continuous grout to the internal angle — will it matter?

Yes, significantly. Grouting internal angles is a deviation from BS 5385-1 and BS 5385-3. The installer carries the liability for any subsequent tile or grout cracking at those angles. In practice, if the substrate is very stable (a rigid slab with no significant deflection) and the room is small, the joint may survive — but it cannot be guaranteed. Explain the standard to the client and document their instruction if they insist.

What silicone should I use in a shower?

Use a neutral-cure (non-acetoxy) silicone in showers and areas where there are metal fittings — acetoxy silicone releases acetic acid as it cures, which can cause corrosion staining on metal components. For shower enclosures, use a sanitary-grade silicone with a long-term mould-resistant formulation (Dow Corning 785, Everbuild All Seasons, Soudal Sanitec) colour-matched to the grout.

Can I replace silicone joints with grout if the silicone goes mouldy?

You can remove old silicone and install new silicone — that is the correct remedy. You cannot replace the joint with grout, as this removes the movement joint function and will cause cracking. To prevent mould recurrence, improve ventilation, use an anti-mould silicone sealant, and advise the client to run the extractor fan for at least 15 minutes after every shower.

How do I cut tiles for Schlüter JOLLY profiles?

Cut the tile to the exact width from the last full tile to the external corner, less the thickness of the JOLLY profile face (typically 8–12mm depending on tile thickness). The JOLLY profile replaces the front edge of the tile — do not tile beyond the JOLLY profile.

What is the minimum grout joint for floor tiles?

Rectified (precision-cut) porcelain tiles can be laid with joints as narrow as 1.5–2mm on a flat, fully bonded substrate. The tile manufacturer's recommendation takes precedence. Note that very narrow joints are virtually impossible to maintain precisely over large areas without precise levelling — most residential installations look better at 3mm minimum.

Regulations & Standards

• BS 5385-1:2018 — wall and floor tiling; code of practice for the design and installation of ceramic and mosaic wall tiling

• BS 5385-3:2014 — wall and floor tiling; code of practice for the installation of ceramic floor tiles and mosaics

• BS EN 12004:2017 — tile adhesives; definitions and requirements

• BS EN 13888:2009 — grout for ceramic tiles; requirements and test methods

• BS EN 12002:2008 — deformability of adhesives; test methods

• Schlüter Systems UK: Profile Guide — full product catalogue and technical installation guides

• British Standards Institution: BS 5385 — wall and floor tiling standard

• TTAF: The Tile Association — industry technical guidance and standards

• BAL Technical Advisory — adhesive and grout selection guidance

• Mapei UK: Technical Support — product selection and installation guidance

• grout repair — regrouting existing installations

• pool tiling — pool-specific movement joint requirements

• bathroom floor prep — substrate preparation before tiling

• bath installation — silicone at bath/tile junction