Where and why worktop joints occur, how to form them correctly, what to seal them with, and what to check at handover.
Why joints are unavoidable
Standard postforming worktops come in 3 m and 4 m lengths. Corner, U-shaped, and long straight runs all require joining sections. The joint is the most vulnerable point — water gets in.
Joint types
- Straight butt joint — two edges meeting in a straight line. Simplest and least visible with a precise cut
- 90° corner joint — joining two sections at a kitchen corner. Requires accurate trimming at 45° or square
- Mitre joint (45°+45°) — neater appearance but harder to fit; both edges cut at 45°
- Radius corner — a dedicated curved section; no sharp joint visible
- Joint at the sink — edge running tight to the sink cutout; highest water-exposure risk
How to join correctly
- Worktop connectors (draw bolts) underneath — pull the two sections together without a gap; minimum 2 bolts per joint
- Apply silicone to both faces before tightening — not after; silicone should squeeze out and be wiped flush
- Check the surface is level across the joint before tightening — use a straightedge or spirit level
- Finish the top seam: clear or colour-matched silicone in a thin bead, not a blob
Corner joint: mitre or butt
Two ways to form a corner — each with its own requirements.
- Butt (90°): one edge is visible from the side. Simpler and cheaper to make
- Mitre (45°+45°): both edges are hidden, looks neater. Requires a precise cut — 0.5° error already shows a gap
- Postforming with a rolled front edge: needs a dedicated corner connector or a radius section — a mitre won't work
Joint strip
A metal or plastic strip fitted over the joint. Covers the seam and protects from water, but makes the joint visible.
- Aluminium strip: longer lasting, won't yellow
- Plastic strip: cheaper, but yellows and cracks over time
- Colour: silver, chrome, or matched to the decor — choose to complement the kitchen hardware finish
- No strip (silicone only): possible with a perfect cut and clamp, but any height difference will show
The sink zone
A joint next to or underneath the sink is the highest-risk location. Water exposure is constant.
- Best solution: position the sink on a single unjointed section
- If a joint is unavoidable: keep it as far from the sink as possible — at least 150 mm away
- Renew the silicone at the sink every 2–3 years: it ages and loses elasticity
- Warning signs: dark staining along the seam, swollen chipboard underneath — time to reseal
Key rule: joint + silicone — use sanitary (neutral cure), not construction grade. Acid-cure silicone smells of vinegar and degrades the adhesive under the laminate.
How to check the joint at handover
- Run a finger across the joint: there should be no height difference
- Inspect the seam: the silicone bead should be thin and even, no voids or ridges
- Press the worktop edge at the joint: no flex or creaking
- Check underneath: draw bolts are tight, no gap between the sections