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Harrow on the Hill HA1 · House refurbishment

House refurbishment in Harrow on the Hill

Dormers, garages, garden gaps and boundaries, estate by estate

Each of the Hill’s conservation areas has its own management strategy, adopted in May 2008, and for a house they do not all ask the same things. This page sets out what they say about dormers and extensions in the Village, open gardens on the Mount Park Estate, original garages in the South Hill Avenue conservation area and front boundaries in Roxborough Park, then the borough rules that sit beside them.

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Start here

House refurbishment in Harrow on the Hill at a glance

Which strategy speaks for your house depends on the conservation area it stands in, so begin with Harrow’s map rather than the street name. The Village strategy carries a design guide for its Victorian terraced cottages and houses, covering dormers, extensions and repairs. Mount Park’s guards the private open space and gaps between buildings. South Hill Avenue’s presumes against demolishing original garages, and Roxborough Park and The Grove’s values continuous front boundaries with greenery behind them. All four date from May 2008; where they proposed new Article 4 directions, check Harrow’s current schedule before treating one as a control.

Harrow: Harrow on the Hill Village Management Strategy and design guide, adopted May 2008 (PDF) · Harrow: Mount Park Estate Management Strategy, adopted May 2008 (PDF) · Harrow: South Hill Avenue Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: Roxborough Park and The Grove Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: the eight Harrow on the Hill conservation areas, with appraisals, maps and Article 4 entries

For the whole area, including conservation areas, permissions and working hours, read our Harrow on the Hill renovation guide.

Approved guide prices

What does a house refurbishment cost in Harrow on the Hill?

Cost in Harrow on the Hill depends on depth of work. A cosmetic refurbishment that keeps the existing layout runs £650–£1,250/sqm (typically £90,000–£180,000), while a back-to-brick renovation runs £2,250–£3,250/sqm (typically £275,000–£475,000), excluding VAT. A written scope and site assessment are needed before any project price can be fixed.

Scope of workGuide rateTypical total
Cosmetic — existing layout retained£650–£1,250/sqm£90,000–£180,000
Back-to-brick renovation£2,250–£3,250/sqm£275,000–£475,000
Typical programme16–32 weeks on site

Guide rates exclude VAT and are set by depth of work, not by postcode. Compare scopes in our London refurbishment cost-per-square-metre guide or try the cost calculator.

The buildings

What the 2008 documents record about the Hill’s houses

Beyond describing each area’s character, the 2008 appraisals and strategies note how some houses have already been altered, and what helps a house sit well in its street.

In the Village, the 2008 appraisal says the backs of Nelson Road and Trafalgar Terrace have been subject to a variety of poor extensions and alterations, whose faults are magnified by the open space around them, and that areas of Wellington Terrace have been rather spoiled by modern development. It also records that a number of former shops on West Street and Crown Street were long ago converted into residential use, and that some keep their original shopfronts as integral features.

Harrow: Harrow on the Hill Village Conservation Area Appraisal, adopted May 2008 (PDF)

Sudbury Hill’s strategy lists principles that new work and extensions should respect: apparent bulk is often reduced using dormers and basements, design is often traditional and harmonising though varied, high-quality materials such as timber windows are used, and development follows the slope of the land and respects existing densities. In Harrow Park, the strategy finds a good number of original windows and decorative details, including ironwork and terracotta, and says the dense greenery along boundaries and open driveways softens the street and is part of its special character.

Harrow: Sudbury Hill Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: Harrow Park Conservation Area Management Strategy, adopted May 2008 (PDF)

On the Mount Park Estate, the 2008 strategy lists flooding as a pressure on the pavements and hard surfacing throughout the area, particularly at the entrance to Mount Park Road from Mount Park Avenue, and says the Council would advise the Mount Park Residents Association on raising the kerbstones so that water is channelled into the drains. That is a note about the estate’s paved areas, not an assessment of any house. For a particular address, the government’s long-term flood risk checker gives the picture for the area, not the chance of one property flooding.

Harrow: Mount Park Estate Management Strategy, adopted May 2008 (PDF) · Check long-term flood risk in England

Permissions and local rules

What the strategies ask before a Hill house is altered

Dormers and extensions in the Village

Can a Village cottage take a dormer or an extension?

The Village’s 2008 design guide says that in some instances a dormer window would be unacceptable, and that dormers are often not original features on many of the area’s properties, so adding one may erode a building’s character. Where a dormer is acceptable, its scale, design and position matter, and it should avoid overlapping existing hips and ridges. Any extension should respect the original house in size, bulk and design, and use matching bricks, bonding, pointing, roofing, rainwater goods, windows and doors.

Harrow: Harrow on the Hill Village Management Strategy and design guide, adopted May 2008 (PDF)

Stacks, parapets, pointing and aerials

What does the Village guide expect when a roof is repaired?

When chimney stacks and party parapets are repaired during roofing work, the 2008 guide says any re-pointing or rebuilding must match the original bonding and pointing, and that weatherstruck pointing will not normally be appropriate. Satellite antennae and aerials should, wherever possible, be sited in rear gardens, or, if absolutely necessary, on rear or unexposed elevations only.

Harrow: Harrow on the Hill Village Management Strategy and design guide, adopted May 2008 (PDF)

Gardens, gaps and original garages

Can a Mount Park or South Hill Avenue house fill more of its plot?

The Mount Park Estate strategy makes a presumption against proposals to infill private open space and natural gaps between buildings, especially where this affects the character of the building, where good views are evident or where the land is Metropolitan Open Land. In the South Hill Avenue conservation area, the strategy presumes against the loss of original garages through demolition. Both said in 2008 that the Council would consider further Article 4 directions; the schedules Harrow publishes today do not show those as made, so read these points as guidance.

Harrow: Mount Park Estate Management Strategy, adopted May 2008 (PDF) · Harrow: South Hill Avenue Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: Mount Park Estate conservation area schedule and Article 4 directions, 1990 and 2021 (PDF) · Harrow: South Hill Avenue conservation area schedule and Article 4 directions, 1991 and 2021 (PDF)

Front boundaries, driveways and original features

Can a front garden become a drive in Roxborough Park or Harrow Park?

Roxborough Park and The Grove’s strategy counts continuous boundary treatments, with private greenery behind them softening the street, as part of the area’s special character, and says the introduction of driveways detracts from this. Harrow Park’s strategy says hard, solid boundary treatments and the removal of original features would severely detract. In 2008 both suggested Article 4(2) directions, but Harrow’s Roxborough sheet lists directions on named properties only, and none of that kind is confirmed for Harrow Park, so, unless a current direction covers your address, treat both as guidance rather than Article 4 controls.

Harrow: Roxborough Park and The Grove Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: Harrow Park Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: Roxborough Park and the Grove conservation area schedule and Article 4 directions, 1988 and 2021 (PDF)

Working hours, skips, parking and the conservation area maps for the whole area are in our Harrow on the Hill guide. Local guidance checked ; requirements depend on the address, the building and the complete proposal.

What the work covers

The parts of a Hill house a refurbishment takes in

Roof, stacks and rainwater goods

The survey starts at the top: the roof covering, chimney stacks and pots, party parapets, any dormers, and the gutters, hoppers and downpipes. Each is marked for repair, overhaul or replacement, and brick, mortar and pointing samples are agreed before scaffolding goes up. A new dormer or roof window is drawn only once the conservation area and what its strategy says are known.

Rooms, services and the floors in the roof

Inside, heating, wiring, plumbing, insulation and finishes are planned as one sequence, so that floors and walls are opened once rather than several times. Rooms in the roof are checked for headroom, structure and a safe way out before they are reused. Any bathroom work is planned with the rest, so that pipe runs, floor levels and extract routes are settled once for the whole house.

Drains, sewers and papers for past work

Public drains and sewers near a planned extension are found on the Thames Water sewer map before it is drawn. Harrow’s charges note for applications from 6 April 2026 rules out the building notice route for an extension over a public drain or sewer, or within 3 m of one, and requires full plans instead. Papers for older extensions, lofts and garage changes are collected at the same time, so that gaps show up early.

Harrow Building Control: domestic charges, Scheme No.15, Tables B and C, for applications from 6 April 2026 (PDF)

How we work

How we run a Harrow on the Hill house refurbishment

  1. Free feasibility visit

    We walk round the house with you and discuss what is feasible.

  2. Survey

    Rooms, levels and features to keep are measured, with opening-up or asbestos checks where needed.

  3. Design and consents

    Our own architects and structural engineers design the layout and structural openings, plan the service routes with them, and identify which consents and party wall notices apply.

  4. Price and contract

    A fixed written price and a JCT contract follow the survey, scope and specification. It records allowances, exclusions and how changes are priced.

  5. On site

    Work is inspected before it is covered, and a director reviews key decisions.

  6. Handover

    Testing, commissioning and snagging. Completed work carries a 12-month defects-rectification period under the JCT contract terms.

Real projects, clearly located

Examples of our house refurbishment work elsewhere in London

None of these projects is in Harrow on the Hill. Each card names where the work was done, so you can judge the finish and the approach before you brief your own.

Your brief

Before you ask for a quotation

  1. Find your conservation area and its strategy

    Enter your postcode in Harrow’s conservation area search, then open the map for the area it returns. Note which of the eight 2008 strategies applies and whether your house number is on that area’s Article 4 schedule. A postcode alone will not settle any of this, so check the exact address.

  2. Say what has already been added

    Tell us what the house is, whether detached, semi-detached, terraced or a cottage on the pavement, and what has changed since it was built: rear additions, dormers, a garage, a new drive or replacement windows. Dates and any approval papers help, because they show what was consented and what may need a second look.

  3. List the outside work separately

    Keep work to the roof, chimneys, walls, windows, garage, garden and front boundary apart from the work inside, and mark which elevations face a road, a path or open space. On the Hill, the outside changes are where the strategies and any Article 4 direction come into play.

Ready to take the next step? Send the address and a short outline of the work.

Book a free feasibility visit

Questions before you begin

House refurbishment in Harrow on the Hill: questions

Can a Hill house have a two-storey rear extension?

Harrow’s 2010 Residential Design Guide is the borough-wide baseline, and a Hill strategy may ask for more. For a mid-terraced house, it generally sees no scope for a first-floor or two-storey rear extension, given the effect on the neighbouring houses and gardens, and it assesses an end-of-terrace house as if it were semi-detached. Where an upper-floor rear extension needing permission would sit against a side boundary, it must satisfy the 45 Degree Code, and, among the site considerations it is assessed against, placing it south or west of the house next door is normally unacceptable.

Harrow: Residential Design Guide Supplementary Planning Document, adopted 15 December 2010 (PDF, file 23276)

How does the 45 degree code treat a neighbour’s bathroom window?

Picture a line at 45 degrees, drawn on plan from the nearest corner of the house next door: its first-floor or two-storey front or rear corner, or a single-storey rear corner if that back wall has a protected window. Under the code in the adopted Local Plan, no part of a new extension should cross it, and projecting eaves are included while shallow fascias and guttering are not. Harrow’s 2010 design guide says bathroom, hall and utility room windows do not count as protected, and the plan warns against applying the code mechanistically.

Harrow Local Plan 2021–2041, the adopted plan (PDF) · Harrow: Residential Design Guide Supplementary Planning Document, adopted 15 December 2010 (PDF, file 23276)

Does Harrow’s flood policy affect a new basement?

Yes, in two ways. On a site in Flood Zone 3b, policy CN3 of the adopted Local Plan rules out basement development altogether. On other sites, anyone forming a new basement, or changing the use of one that already exists, must address flood risk in the Flood Risk Assessment, and resilience measures will be required. CN3 also says proposals for new homes or extra habitable rooms in basements will be refused. That sits alongside the separate basement policy, so say at the outset what the lower floor is for.

Harrow Local Plan 2021–2041, the adopted plan (PDF)

Did the 2008 strategies’ proposed Article 4 directions come into force?

Not as far as Harrow’s published schedules show. The 2008 strategies proposed or suggested further directions, for example on driveways in Roxborough Park, on original garages in the South Hill Avenue conservation area, and on roof tiles, rooflights, extensions and alterations on the Mount Park Estate. The sheets Harrow publishes today list other directions for those areas, not these. Treat the proposals as the Council’s guidance, and check the current schedule for the exact address before relying on any control.

Harrow: Roxborough Park and The Grove Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: South Hill Avenue Conservation Area Management Strategy, adopted May 2008 (PDF) · Harrow: Mount Park Estate Management Strategy, adopted May 2008 (PDF) · Harrow: Roxborough Park and the Grove conservation area schedule and Article 4 directions, 1988 and 2021 (PDF) · Harrow: South Hill Avenue conservation area schedule and Article 4 directions, 1991 and 2021 (PDF) · Harrow: Mount Park Estate conservation area schedule and Article 4 directions, 1990 and 2021 (PDF)

Does a house project need a flood risk assessment?

Some will. Harrow will not validate an application that needed a Flood Risk Assessment and arrived without one. The applications on which it consults the Environment Agency include those in flood zones 2 and 3, and smaller ones in flood zone 1 where an area has critical drainage issues. The West London Strategic Flood Risk Assessment, which Harrow shares with five other boroughs, offers an interactive flood zone map, so look up the address on it before an extension or basement is designed.

Harrow: West London Strategic Flood Risk Assessment and flood risk assessments

How much does a house refurbishment cost in Harrow on the Hill?

It depends on scope. In Harrow on the Hill, a cosmetic refurbishment keeping the existing layout runs £650–£1,250/sqm (typically £90,000–£180,000); a back-to-brick renovation runs £2,250–£3,250/sqm (typically £275,000–£475,000), excluding VAT. A written scope and site assessment come before any fixed price.

Book a free feasibility visit

Talk to us about your Harrow on the Hill house

Tell us the address and what you want to change in your Harrow on the Hill house. We reply within one working day, Monday to Friday, 8am to 6pm.

Or call 020 7101 3168. We serve Harrow on the Hill from our studio at Unit 3, Palace Court, 250 Finchley Road, London NW3 6DN.

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