Corbett Estate Catford: Pinhole Leaks Under the Floor

Yes, it is quite possible. Corbett estate houses have suspended timber ground floors over a damp void, and the copper pipes running through that void corrode slowly from the outside until a pinhole opens. The signs are a musty smell, boards that feel soft or lift, mould along the skirting, or a water meter that moves with every tap off. A leak like this is best found with thermal imaging or acoustic listening first, so only one or two boards come up in the right place, and a short section of pipe is replaced or re-routed.

The Corbett estate in a paragraph

Archibald Cameron Corbett began building on about 280 acres of North Park Farm in 1896, and over roughly fifteen years put up more than 3,000 houses on 27 streets, many with Scottish names, between Hither Green and Rushey Green. He famously allowed no pubs. The houses were built to a consistent pattern, which is why so many of them now fail in the same ways.

Why the floor void is the weak spot

Ground floors in these terraces are timber boards on joists, with a void underneath and airbricks in the front and back walls to ventilate it. Over the decades:

• airbricks get blocked by raised paths, patios, render or rubbish;
• the void gets damp, especially in a wet winter on Catford’s clay;
• the copper pipes that were later run through it sit in that damp air for decades;
• any pipe resting on soil, rubble or a damp sleeper wall corrodes faster.

The result is pinholing: tiny holes through the pipe wall that start as a weep and grow. Because they are under the floor, the water soaks into the void and nobody sees it for weeks or months.

There is often a second suspect under the front path: the original lead supply pipe from the street, which Thames Water says was banned in the 1970s. Corbett houses that have never had it replaced still have it.

Signs of a hidden leak under the floor

• A musty, damp smell in the front or back room, worse when the heating is on.
• Floorboards that feel soft, spongy or slightly raised.
• Mould or a tide mark along the bottom of the skirting.
• Carpet grippers rusting or carpet feeling damp at the edge.
• A boiler pressure gauge that keeps dropping (heating pipe).
• A water meter that moves when every tap is off (mains pipe).
• Higher water bills with no change in use.

Check before anyone lifts a board

1. Turn off every tap and make sure no appliance or toilet is filling.
2. Find the water meter, usually in a pavement box outside, and photograph the reading.
3. Use no water for an hour, then read it again.
4. If it has moved, there is a leak somewhere on the mains side.
5. Note the boiler pressure morning and evening for a few days to check the heating circuit.
6. Check that the airbricks front and back are clear, and look for any wet patches in the cupboard under the stairs.

How we find it with minimum disruption

The aim is to know where the leak is before lifting anything.

• Thermal imaging shows warm water from a heating pipe spreading under the boards.
• Acoustic listening picks up the hiss of a pressurised mains leak through the floor.
• Tracer gas is useful when the void is deep or the pipe run is long.
• Pressure testing isolates sections to confirm which run has failed.

Then one or two boards come up over the marked spot. In Corbett houses the boards are often original, so we lift them carefully and put them back.

Repairing it

A single pinhole can be cut out and a new section fitted. But if the rest of the pipe in the void is the same age and condition, another pinhole nearby is likely. Often the better answer is to:

• replace the whole run under that floor with new pipe, clipped clear of the ground;
• or re-route it above the floor, along the skirting or through a ceiling.

At the same time, it is worth making sure the airbricks are clear so the void dries out. We will explain the options and agree the price with you before we start.

The other Corbett estate classic

Many Corbett houses have had a bathroom built over the kitchen extension at the back. The joint between the two is the commonest ceiling stain in the postcode. If you are seeing a stain on the kitchen ceiling rather than damp under the front room, read our guide to a kitchen ceiling stain under the bathroom.

Insurance and water bills

Many buildings policies cover the damage from escaped water, and some include trace and access, which pays to find the leak and make good. The worn pipe itself is usually not covered. If the leak is on the mains and you are metered, Thames Water says you must fix it within four weeks of knowing about it, and you may be able to claim a leak allowance.

When to call

Call us if your meter moves with everything off, the boiler keeps losing pressure, or the floor smells damp and feels soft. We cover leak detection in Catford and water leaks in Catford, including Hither Green and Bellingham. More on the area is on our Catford area page.

Need a plumber now?

Call 07868 281022 and tell us your postcode, what you have noticed (smell, soft floor, meter moving), and whether the water is off. We agree the price with you before any work starts.