Loft
conversions
in Hampstead Garden Suburb, NW11
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Loft rooms for Suburb houses, designed from the roof first: its pitch, its clay tiles and whether it can take a dormer or only a single rooflight, then the stair, the insulation and the rooms the space can hold.
A Suburb loft conversion needs the Trust's consent even in a freehold house, because converting a loft almost always shows on the outside. With permitted development rights removed by the Article 4 Direction, an attic room lit by dormers or rooflights may need planning permission from Barnet as well.
So we design a Suburb loft from the roof inward: what the roof can take first, then the rooms it can hold.
Sources: Hampstead Garden Suburb Trust: Planning FAQs, Hampstead Garden Suburb Trust and Barnet Council: Conservation Area Design Guidance (2010)
Steep Plain-Tile Roofs and What They Allow
Most Suburb houses have steep plain-tile roofs, typically 45 to 55 degrees, and matching handmade clay tiles must be used when a roof is altered.
The joint guidance says converting roof space is often possible if carefully designed, beginning with whether dormers or rooflights are needed and where they could sit.
Small cottages were designed as two-storey buildings, and loft conversions with dormers on them will generally not be acceptable.
We measure the ridge height, the pitch and the usable floor area before drawing anything, because a roof that cannot take a dormer may still take a single rooflight.
Source: Hampstead Garden Suburb Trust and Barnet Council: Conservation Area Design Guidance (2010)
Dormer Size, Position and Detail
Where dormers are acceptable they should be in proportion to the roof, generally sit in the middle third of the slope and face the rear or side; front dormers are generally not acceptable.
New or replacement dormers must match original details exactly while meeting modern building regulations where possible. The guidance puts it plainly: nothing is less convincing than a near match.
On a semi-detached house a dormer must not unbalance the pair, and dormers next door are not necessarily an argument for one on yours.
A large dormer next door that does not conform to the current guidance will not usually count as a precedent, the Trust says.
Sources: Hampstead Garden Suburb Trust and Barnet Council: Conservation Area Design Guidance (2010), Hampstead Garden Suburb Trust: Planning FAQs
Rooflights and Crown-Roof Skylights
Small traditional rooflights may be acceptable in discreet places, generally one per slope and not on the front, of a slim conservation type normally no larger than 460 by 610mm.
The Trust's rooflight guidance asks for them to be fitted flush with the roof covering, with any new tiles matching the roof around them.
Flat-topped crown roofs may allow concealed flat-topped skylights.
Sources: Hampstead Garden Suburb Trust and Barnet Council: Conservation Area Design Guidance (2010), Hampstead Garden Suburb Trust: Technical Guidance on Rooflights
Insulating and Ventilating the New Room
The Trust's retrofit guidance says habitable roof spaces are usually insulated between the rafters; insulating on top of them would raise the roof and is unlikely to be acceptable.
New insulation must not block ventilation at the eaves, and any extra roof vents must be a type the Trust approves.
Loft and roof insulation is on the Trust's list of work that needs its consent.
Source: Hampstead Garden Suburb Trust: Home Retrofit Guidance
Stairs, Floors and Fire Safety
The Planning Portal says building regulations approval is required to turn a loft into a liveable space.
Existing loft joists in most homes were not designed to carry significant load; they tie the roof together and hold up the ceiling below.
A new stair is needed to serve loft rooms, and retractable ladders are not normally acceptable; a typical conversion also needs fire-resisting doors protecting the stair and interlinked smoke alarms.
The Trust asks for a section through the loft stair in the application, and dormer proposals need large-scale drawings with construction details at 1:10.
Sources: Planning Portal: Is building regulations approval needed for a loft conversion?, Planning Portal: Loft conversion, building regulations: stairs, Planning Portal: Loft conversion, building regulations: fire safety, Hampstead Garden Suburb Trust and Barnet Council: Conservation Area Design Guidance (2010)
A loft conversion we completed nearby
Questions about a Suburb loft conversion
Does a loft conversion in the Suburb need the Trust's consent?
Yes. The Trust excludes loft conversions from the freedom freeholders have for interior work, because they almost always change the outside.
Can I put a dormer on the front of my roof?
Generally not. The joint guidance says dormers should in most cases be on rear or side slopes.
Will a dormer be allowed because my neighbour has one?
Not necessarily. The guidance says neighbouring dormers are not necessarily an argument for yours, and work that breaks the current guidance will not usually be treated as setting a precedent.
How large can a rooflight be?
Normally no larger than 460 by 610mm, of a slim conservation type, generally one per slope and not on the front.
Can I convert the loft of a small cottage?
Dormer conversions will generally not be acceptable on small cottages designed as two-storey buildings; on modest houses a small rooflight in a discreet position may be the alternative.
Sources: Hampstead Garden Suburb Trust: Planning FAQs, Hampstead Garden Suburb Trust and Barnet Council: Conservation Area Design Guidance (2010)
Sources
- Hampstead Garden Suburb Trust: Planning FAQs
- Hampstead Garden Suburb Trust and Barnet Council: Conservation Area Design Guidance (2010)
- Hampstead Garden Suburb Trust: Technical Guidance on Rooflights
- Hampstead Garden Suburb Trust: Home Retrofit Guidance
- Planning Portal: Is building regulations approval needed for a loft conversion?
- Planning Portal: Loft conversion, building regulations: stairs
- Planning Portal: Loft conversion, building regulations: fire safety
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