How do I drill a tap hole in a laminate or wooden worktop?

This is the hole that ruins worktops. A laminate top is a chipboard core with a thin decorative layer that chips if the cutter tears it, and a core that swells like a sponge if water reaches it. Both failures are avoidable and both are common, and the sealing step is the one nobody does.

Safety

What you'll need

• Hole saw or Forstner bit of the exact tap size
• Drill with a side handle, gear 1
• Clamps and scrap timber for support
• Masking tape (optional)
• Silicone sealant or varnish for the cut edge
• Tap and its fixing kit, to check the size

Step by step

1. Get the size from the tap, not from a chart.Most monobloc taps take a specific hole diameter, and the fitting instructions state it. Cutting a hole that is a couple of millimetres oversize means the tap base does not cover it.
2. Set the position out fully.Check the tap will clear the window, the tiles, the sink edge and the wall, and that the tails and fixing bolts will clear the sink bowl and the cupboard back beneath. Sit the tap in place with the sink to confirm before cutting.
3. Support the worktop underneath.Clamp scrap timber under the cut area, hard against the underside. It supports the laminate at breakthrough and prevents the core blowing out.
4. Tape the surface.Masking tape over the whole cut area reduces chipping of the laminate at the rim and lets you mark clearly on it.
5. Drill from the decorative face.The teeth of a hole saw pull downwards, so they cut cleanly on entry and tear on exit. Entering on the face you will look at puts the tearing on the underside.
6. Run slowly in gear 1 and let it cut.A large hole saw at speed burns the laminate, glazes the teeth and smokes. Low speed, moderate pressure, and withdraw regularly to clear dust.
7. Stop when the pilot breaks through.As soon as the pilot bit's point appears on the underside, stop. Turn the worktop over if you can, or work from below, and cut the last part from the other side so the two cuts meet.
8. Seal the cut edge before fitting anything.Paint the raw chipboard inside the hole with silicone, varnish or a proprietary edge sealer and let it cure. Water always gets to a tap hole eventually, and unsealed chipboard swells and lifts the laminate.
9. Bed the tap on sealant too.A ring of silicone under the tap base and under any backing washer, so water on the surface cannot track into the hole. Wipe the squeeze-out before it skins.

Tips

• A Forstner bit gives a cleaner rim than a hole saw in laminate, and a hole saw is faster and cheaper. For a hole that will be entirely covered by the tap base, the hole saw is fine.
• In a solid wood worktop, seal the hole with the same oil or finish used on the rest of the top, and re-oil around the tap regularly. Wood tops fail around taps more often than anywhere else.
• If the worktop is already fitted and you cannot get underneath, take the extra care at breakthrough and accept a rougher underside. The support block is still worth clamping from below.

Common mistakes

• Cutting all the way through from the top in one go — The hole saw tears the underside out as it exits, and in a fitted top that means a ragged hole and a weakened core exactly where the tap clamps.
• Leaving the core unsealed — Chipboard swells enormously when wet and never recovers. The laminate lifts and bubbles round the tap, and the only repair is a new worktop.
• Running the hole saw fast — It burns the laminate brown at the rim, glazes the teeth and can set the dust smoking. Slow is the whole technique.

Questions people ask