Why drains fail in Hendon & Golders Green

Hendon & Golders Green sits on London Clay throughout, with the Dollis Brook and Silk Stream draining the area towards the Brent. The housing is largely Hampstead Garden Suburb, laid out from 1907 and now almost entirely a conservation area, alongside interwar semis through Hendon and Colindale and larger houses at Mill Hill. Those two facts between them explain most of what we dig up here, because the ground decides how a pipe is loaded and the age of the building decides what the pipe is made of.

The Dollis Brook, Mutton Brook and Silk Stream all converge on the Brent at Brent Cross, and the Welsh Harp reservoir sits at the bottom of the catchment. That matters for drainage because water in the ground and water in the pipe are the same problem seen from two sides: a defect lets one become the other.

In practice, the recurring causes of drainage failure we find across Hendon & Golders Green are:

London Clay shrink and swell, which on this ground is among the most severe in London and is the root cause of most fractured pipework here.
Mature trees on the garden suburb and Mill Hill plots, planted as part of the original layouts and now large enough to find any open joint.
Conservation area coverage across Hampstead Garden Suburb, which effectively rules out excavating front gardens and driveways.

None of this is unusual or alarming on its own. Buried clay pipework has a service life, and across most of this area that life is either over or close to it. The useful question is not whether a drain will eventually need work, but whether the defect you have now needs a patch, a full lining, or an excavation.

Drain repair in Hendon & Golders Green

Drain repair covers structural damage to the pipe: fractures, open joints, displaced sections, deformed pipe, and full or partial collapse. These are the faults that produce blockages which come back within weeks of being cleared, because the clearance removes the debris but leaves the thing that caught it.

We survey the run first with a CCTV camera and code the defects against the standard drain condition classification, so what you are told matches what a surveyor, an insurer or a buyer’s solicitor would independently record. On the ground conditions typical of Hendon & Golders Green, the usual outcome is one of three things: a localised patch liner over a single fracture or open joint, a full-length liner where the pipe is defective along its whole run, or an excavation and replacement where the pipe has collapsed and there is no longer a bore to line.

Excavation is the last option rather than the first, and not only on cost. Digging out a drain means taking up whatever is above it, which in a lot of properties here means a driveway, a patio, a rear extension floor or a front garden inside a conservation area. Where the pipe can be repaired from the inside, that is nearly always the better answer.

Drain resealing and relining in Hendon & Golders Green

Resealing addresses the joints rather than the pipe body. Older clay drainage was laid in short lengths with mortar or rubber joints, and it is the joints that open first: they take the movement, they let roots in, and they let groundwater and soil out and in. A drain can be structurally sound along every length and still be failing entirely at its joints.

Where the joints have opened but the pipe is otherwise intact, sealing them is a much smaller job than replacing the run. Depending on what the survey shows, that means resin injection into the joint from inside the pipe, a short patch liner bridging the joint, or a cured-in-place liner along the whole length that leaves a continuous jointless pipe inside the old one.

Relining is particularly worth considering in Hendon & Golders Green because so much of the housing stock is listed or inside a conservation area that excavating a frontage is either refused or slow enough to be impractical. A liner is installed through an existing access point and leaves the surface untouched.

A cured-in-place liner reduces the internal diameter slightly, so it is not the right answer on a pipe that is already undersized or badly deformed. We say so when that is the case rather than lining something that should be dug up.

Cracked and leaking drain repair in Hendon & Golders Green

A leaking drain is often the least visible and most expensive of the three. There may be no blockage at all. What you see instead is damp at the base of a wall, a persistent drain smell in a garden or a downstairs room, ground that stays soft in dry weather, a sinking path or patio, or in the worst cases cracking in the building above where the ground beneath a foundation has been washed out.

On the ground under Hendon & Golders Green, that last mechanism is worth taking seriously. London Clay does not wash away the way gravel does, so a leak here tends to show as persistent saturation, damp at the base of walls and softened ground rather than a sudden void. It is slower, which also means it usually goes unnoticed for longer.

Finding a leak takes more than a camera. Depending on the case we combine CCTV with a dye test to prove which appliance or gully feeds the defect, and a water test to confirm a section is holding before and after the repair. If the drain runs under a building or a boundary, we trace and depth the run from the surface so everyone knows exactly where it goes before anything is opened up.

How a job actually runs

Survey first. A CCTV survey of the affected run, with the defects located by distance from the access point and coded against the standard classification.
A written report and the footage. You keep both. They are yours to take to an insurer, a managing agent, a neighbour or another contractor for a second opinion.
Options, with the trade-offs stated. Patch, full liner or excavation, with what each one does and does not fix, and what it means for the surface above.
The repair. Carried out to the method agreed, not changed on site without telling you why.
A post-repair survey. The same camera down the same run afterwards, so the finished condition is on record and not just described.

If a survey shows the drain is sound and the problem is somewhere else, we tell you that. A blockage that turns out to be a collapsed gully, a disconnected downpipe or a failed rainwater connection is a different job, and pretending otherwise helps nobody.

Whose drain is it?

This question decides who pays, and it catches people out constantly. On 1 October 2011 most private sewers and lateral drains in England and Wales transferred to the local water and sewerage company. In Hendon & Golders Green that company is Thames Water.

The short version: the drain inside your property boundary that serves only your property is yours. The lateral drain, meaning the length that continues beyond your boundary to the public sewer, is normally Thames Water’s. A shared drain serving more than one property is usually theirs too, even where it runs under your garden. Where a pipe was laid after the transfer date, or serves only your building, it stays private.

This is worth establishing before any work is agreed, because a defect on a Thames Water asset is generally repaired at their cost, not yours. A CCTV survey that locates the defect relative to your boundary is what settles it. Building control and drainage consents for the area sit with the London Borough of Barnet, and any new connection or build-over of a public sewer needs Thames Water’s agreement in advance.

Areas we cover in Hendon & Golders Green

We cover 11 named areas across the NW4, NW7, NW9 and NW11 postcode districts. If your street is not listed but sits between two that are, we almost certainly cover it, so call and ask.

Beaufort Park NW9
Brent Cross NW4
Colindale NW9
Golders Green NW11
Grahame Park NW9
Hendon NW4
Mill Hill NW7
Mill Hill East NW7
Queensbury NW9
Temple Fortune NW11
The Hyde NW9

Common questions

How quickly can you get to Hendon & Golders Green?

Call 07438 912191 and we will tell you honestly when we can be there, based on where our crews already are that day. We would rather give you a real time than a time that sounds good on the phone.

Do I need a CCTV survey before a repair?

For any structural repair, yes. There is no way to specify a patch, a liner or an excavation without seeing the defect, its position and its extent. Anyone quoting a drain repair without surveying it first is guessing at your expense.

Roots keep coming back into my drain. Can that be fixed permanently?

Cutting roots out clears the pipe but does not stop them, because they are coming through a defect. The permanent fix is to seal the way in, either with a patch over the specific joint or a full liner. Once the pipe is sealed the roots have nothing to grow towards.

Is my drain in Hendon & Golders Green my responsibility or Thames Water’s?

It depends where the defect is. Pipework inside your boundary serving only your property is yours. The lateral drain beyond your boundary, and shared drains serving more than one property, generally transferred to Thames Water in October 2011. A survey that locates the defect relative to your boundary is what settles the question, and it is worth settling before you agree to pay for anything.

Nearby areas we also cover

See every area we cover · Drain repair · Drain resealing · Leaking drain repair

Drain Repair in Hendon & Golders Green