House
extensions
in Primrose Hill, NW1
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Hampstead Chartered Surveyors & Building ConsultancyExtending a Primrose Hill house is mostly about the back of the terrace: what neighbours see from their gardens, and what the rest of the row already has.
The statement asks for extensions to follow the original form of the house and the historic pattern of extensions in its terrace or group, with larger ones depending on the site.
We draw the rear of the whole terrace before designing one house's extension, so the proposal can show how it fits the row.
Source: Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001)
Rear extensions in a Primrose Hill terrace
Rear extensions should be as unobtrusive as possible and, in most cases, a single storey, with their effect on neighbours and the conservation area deciding the rest.
They will not be acceptable where they would spoil the uniform back of an unspoilt terrace or group.
Camden's wider guidance asks for rear extensions to be subordinate to the house and to leave a reasonably sized garden.
Sources: Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001), Camden Planning Guidance: Home Improvements (January 2021)
Side extensions and the gaps between houses
Side extensions are not acceptable where they are unduly prominent, unbalance a group or close gaps through which there are views of houses, gardens, mature trees or the Regent's Canal.
Camden's guidance says side extensions should generally be single storey.
Narrow plots on parts of Regent's Park Road already leave the backs of houses there visible from the street and from Regal Lane.
Sources: Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001), Camden Planning Guidance: Home Improvements (January 2021)
Conservatories and garden rooms
Conservatories, like extensions, should be small in scale, subordinate to the house and at ground floor level only.
Rooflights on a ground floor extension should be placed away from the building line or use obscured glazing, to limit light spill on neighbours.
On a flat roof, Camden prefers a biodiverse green roof with at least 100mm of substrate to a sedum blanket.
Sources: Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001), Camden Planning Guidance: Home Improvements (January 2021)
Daylight and neighbours
Camden's guidance tests a rear extension against its 45 degree and 25 degree rules, or against BRE daylight guidance through a study.
Extensions should also avoid excessive light spill on neighbours, including flats above where a house has been divided.
We prepare the daylight drawings early, because the angles often set the depth and height of a Primrose Hill extension.
Source: Camden Planning Guidance: Home Improvements (January 2021)
Permitted development and Article 4 here
Government guidance says that in conservation areas, extending beyond a side wall and rear extensions of more than one storey are not permitted development.
Many Primrose Hill houses have also lost their extension rights under the Article 4 direction, which mainly covers extensions and alterations.
A Lawful Development Certificate gives certainty where a proposal is thought to need no application.
Sources: MHCLG: Permitted development rights for householders, Technical Guidance (September 2019), Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001)
Trees, foundations and drains
Six weeks' notice is needed before pruning or felling a tree in the conservation area, and trees that contribute to it should be kept and protected through the work.
Clay soils can move with moisture, so foundations may need to go deeper, especially near trees.
Building over or within 3 metres of a drain or sewer brings in Approved Document H.
Sources: Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001), Planning Portal: Extensions, Building Regulations: Foundations, GOV.UK: Approved Document H, Drainage and waste disposal (2015 edition)
Structure and building regulations
Most extensions need building regulations approval.
Where the extension opens into the house, the wall above the new opening is carried on beams, and steel is normally protected against fire.
Next to a neighbour's wall, it is good practice to dig at least as deep as the bottom of their foundation.
We commission the engineer's design before the extension is priced, because the foundations and the opening are usually the largest structural costs.
Access matters as much as design on these streets. Where a terrace has no side way, materials and spoil travel through the house, so we protect floors and stairs along that route and plan the build in loads that will pass through the front door.
Sources: Planning Portal: Is building regulations approval needed for an extension?, Planning Portal: Extensions, Building Regulations: Structural Opening, Planning Portal: Extensions, Building Regulations: Foundations
Brick, glass and the back of a terrace
Most Primrose Hill extensions are seen against a long row of rear elevations, so we choose a brick that weathers to match the terrace, keep the parapet line low and set the glazing in deep reveals rather than in a full glass wall.
Where a neighbour has already extended, we line the new roof and the party wall up with theirs, so the row reads as a sequence rather than a collection of one-offs.
Asking Camden before you apply
Camden's pre-application service offers homeowners two levels of advice, and says it makes a successful application more likely.
The first level covers work such as one single-storey rear extension; the second covers more complex schemes, such as more than one extension or a two-storey one.
Camden asks for a summary of the proposal, labelled drawings or sketches and photographs with the request.
For a Primrose Hill extension we include a drawing of the whole terrace's rear elevation and photographs from the garden and the neighbours' side, because the council will judge the scheme against the row, not the house alone.
The advice is then used to settle the extension's depth, height and materials before the full application is drawn.
Sources: Camden Council: Pre-planning application advice for homeowners, Camden Council: Conservation areas
A Primrose Hill extension
Questions about extending a Primrose Hill house
Can I build a two-storey rear extension?
It is unlikely: the statement expects most rear extensions to be a single storey and judges larger ones on the site.
Will Camden accept a side extension?
Only where it is not prominent and does not close a gap that gives views of gardens, trees or the canal.
Do I have permitted development rights?
Possibly fewer than elsewhere: many houses here lost extension rights under the Article 4 direction, and conservation areas restrict some extensions nationally.
How is daylight to neighbours checked?
Camden applies its 45 degree and 25 degree tests, or a daylight study to BRE guidance.
What should go on a flat extension roof?
Camden prefers a biodiverse green roof with at least 100mm of substrate over sedum.
What does a house extension in Primrose Hill cost?
Pricing: quoted after a feasibility visit.
Sources: Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001), MHCLG: Permitted development rights for householders, Technical Guidance (September 2019), Camden Planning Guidance: Home Improvements (January 2021)
Sources
- Camden: Primrose Hill Conservation Area Statement (adopted December 2000, published January 2001)
- Camden Planning Guidance: Home Improvements (January 2021)
- MHCLG: Permitted development rights for householders, Technical Guidance (September 2019)
- Planning Portal: Extensions, Building Regulations: Foundations
- GOV.UK: Approved Document H, Drainage and waste disposal (2015 edition)
- Planning Portal: Is building regulations approval needed for an extension?
- Planning Portal: Extensions, Building Regulations: Structural Opening
- Camden Council: Pre-planning application advice for homeowners
- Camden Council: Conservation areas
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