House Extension Gipsy Hill SE19 Where the Houses Are Still Moving
An application went to Lambeth for a poplar in a back garden on Gipsy Hill. The stated reason was not light, or leaves, or roots in a drain. It was to stop the influence of the tree on the soil below building foundation level, and to provide long term stability. Somebody was watching their house move.
That is the honest starting point for building work here. Lambeth describes the conservation area as piecemeal nineteenth century suburban development which rises up Gipsy Hill, and every part of that sentence matters. Piecemeal, so no two neighbouring houses were necessarily built by the same hand. Nineteenth century, so shallow foundations. And rising, because the ground climbs steeply enough to give views across Dulwich to the City.
Around ten and a half thousand people live in the ward, in slightly under a square kilometre. It is mostly Victorian, it sits on London Clay, and it is one of the few parts of south London where a homeowner’s first question is more often about a crack than about a kitchen. Design And Build works across SE19 with every discipline the job needs on our own staff.
Climbing ground: house extension Gipsy Hill
Retaining walls on ground that will not stay put
A plot with a fall across it is a different job from a level one, and most plots here have one. The garden either drops away behind the house or climbs above it, and both need solving before a design is fixed.
Falling ground wants stepped footings and frequently a retaining structure along a flank, with a good deal more spoil off site than a flat site produces. Rising ground turns the problem into light and overlooking instead. A retaining wall is a structural element, not landscaping, and on clay it has to resist ground that swells when wet. Our engineers take levels across the whole plot before anyone talks about square metres.
The lower floor you already own
Because the streets climb, a great many houses here have a lower ground floor that has never been much used. That is space you have already bought.
One Gipsy Hill application covered converting a lower ground flat into two, with a side addition where a garage had stood and new lightwells for amenity. Another, further down the hill, took commercial floorspace at lower ground and ground level into four homes. Digging out headroom and forming a lightwell often costs less than building outward, and it leaves the street elevation alone. Interior design joins once the levels are settled.
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Builders Gipsy Hill on clay and a gradient
Underpinning and subsidence in SE19
Clay shrinks as it dries and swells as it wets. A Victorian foundation laid shallow moves with it, and on a slope the movement is rarely even across the building.
That produces the diagonal cracking above windows and doors that people photograph and send to us. Not every crack means underpinning: a great many are historic, stable, and need nothing more than monitoring and repair. The ones that matter are widening, seasonal, and worse at one corner. Establishing which you have is a survey and a monitoring period, not a guess, and it comes before any decision about extending.
A poplar, a foundation and long term stability
Trees are usually the mechanism. A mature poplar draws a great deal of water out of clay in a dry summer, and the ground beneath a nearby foundation contracts as it does.
Which is why that Gipsy Hill application asked to remove one. But felling is not automatically the answer, and it is not automatically permitted either: inside a conservation area every tree is protected and six weeks’ notice must reach the council, and individual Tree Preservation Orders apply elsewhere. Removing a large tree can also let clay rehydrate and lift the ground, which brings its own problems. The tree, the ground and the foundation are one question.
House renovation Gipsy Hill on Victorian stock
CA14 and CA23, and what neither removes
Two conservation areas reach into SE19. The Gipsy Road conservation area, reference CA14, was designated in 1974, extended in 1982 and revised in 1999. Westow Hill North Side, CA23, covers the northern frontage at the top of the hill.
What neither carries is an Article 4 direction over householder work. Lambeth has four directions across sixty-five conservation areas; three restrict commercial to residential conversion and the fourth covers houses in multiple occupation in Streatham. None of them reaches here. So inside the conservation areas the national rules narrow as they always do, but the additional layer that catches Forest Hill or Brockley homeowners does not apply. That is worth knowing before you assume the worst.
A listed tower somebody lives in
The landmark on the hill is the tower of Christ Church. The Victorian church behind it is gone; the tower survives, is listed at Grade II, and is a private dwelling.
It is a useful thing to point at, because it shows what this area actually is: nineteenth century fabric adapted to live in rather than preserved behind glass. Most SE19 renovation is that job on a smaller scale — solid brick in lime mortar, sash windows worth repairing rather than replacing, and services installed by four generations of previous owners.
Everything in-house: construction company Gipsy Hill
A project here can involve a structural question, a ground question, a tree question and a conservation question, and the honest position is that they are the same question asked four ways.
Splitting them across four appointments means each answer arrives without reference to the others. Inside one construction company the survey, the drawings, the engineering and the build are the same conversation. Surveyors we employ deal with the Party Wall etc. Act 1996, we lodge with Lambeth ourselves, and where the work needs no permission a lawful development certificate records it. One agreement, one price, one person accountable.
Area We Cover
Bring us the cracks before you bring us the plans
If something is moving, that gets settled first. There is no sense designing an addition onto a building whose foundations are still finding their level, and no sense underpinning a wall you were about to take out.
Send photographs and the address. What comes back tells you whether it looks like historic movement or active, what the trees and the ground are likely to be doing, whether either conservation area touches the address, and what permitted development remains. Our patch is Gipsy Hill and SE19 — Gipsy Road, Salter’s Hill, Central Hill, Woodland Road, Highland Road and the streets off them — along with Norwood, Herne Hill, the Lambeth borough and the SE postcodes around it.
Surveys are free. On this hill we start with the ground, not the drawings.
