Harrow is classic Metro-land: tree-lined interwar suburbs around Pinner, Rayners Lane, Kenton and North Harrow, an older hilltop village centre at Harrow on the Hill, and Green Belt edges at Stanmore and Hatch End. Plots are generous, so adding space rather than moving is what most people here do.
London Building Contractors
Builders in Harrow Homeowners Can Rely On
What We Do
Building Services from Harrow Builders
Every service below is delivered by our own in-house tradespeople, fixed-price and fully insured, so you get dependable builders in Harrow from survey to handover.
Loft Conversions in Harrow
Transform your home with expert loft conversions in London by Alpha London Builders. From design and planning to construction, we deliver quality loft conversions tailored to your needs.
Learn more →House Extensions in Harrow
Rear, side return, wraparound and double storey extensions designed and built to fit seamlessly with your London home.
Learn more →Basement Conversions in Harrow
Cellar conversions, basement lowering and full new excavations, engineered and waterproofed to BS 8102 by our in-house team.
Learn more →Garage Conversions in Harrow
Integral, attached and detached garage conversions into bedrooms, offices and annexes, most without planning permission.
Learn more →Property Refurbishment in Harrow
Cosmetic updates through to full structural refurbishments, managed under one dedicated site manager from start to finish.
Learn more →General Building in Harrow
Repointing, roof repairs, damp treatment, brickwork and small structural alterations, carried out by our own trades.
Learn more →Design & Build in Harrow
One team, one contract, one fixed price for design, planning, structural engineering and construction on your project.
Learn more →New Builds in Harrow
New homes and replacement dwellings built from foundation to final finish, with zero-rated VAT on construction costs.
Learn more →Commercial Building in Harrow
Office, retail and restaurant fit-outs across London, delivered around your trading hours with minimal disruption.
Learn more →Residential Building in Harrow
The full range of residential building work, from a single repair to a new build, delivered by one London contractor.
Learn more →Building Demolition in Harrow
Safe, fully licensed demolition work across London, from internal wall removal to complete house demolition ahead of a new build.
Learn more →Why Choose Us
Why Choose Our Harrow Builders
Metro-land housing know-how
Hipped roofs, side garages and deep gardens are the norm, and our carpenters and bricklayers know how to make good use of them.
Green Belt honesty
Around Stanmore and Hatch End we tell you plainly how much a house can grow before you pay for design.
Garage conversions done properly
We handle insulation, ventilation, fire safety and the planning-condition check that many conversions miss.
Local planning checked first
Harrow on the Hill, Pinner Village and Stanmore Hill each have their own rules, and we check them before pricing.
Local Knowledge
Building & Planning Considerations in Harrow
Harrow has conservation areas including Harrow on the Hill, Pinner Village and Stanmore Hill, and parts of the north of the borough are Green Belt. In Green Belt areas an extension is assessed against the size of the original house, not the plot. Elsewhere, most interwar semis and detached houses keep their standard rights for single-storey rear extensions and rear dormers. Flats and maisonettes have no permitted development rights, and listed buildings need listed building consent for almost any change.
As Harrow builders, every quote we provide for a Harrow property starts with a check against Harrow Council's conservation area maps and Article 4 register, so you know exactly which route your project needs before any design work begins.
Local Guide
Building in Harrow: what to know before you start
Suburbs built for extending
Much of Harrow was built in the 1920s and 30s, with hipped roofs, side garages and gardens deep enough to extend into. Harrow on the Hill and Pinner Village are older and more protected. Stanmore and parts of Hatch End sit near the Green Belt, which affects how large an extension can reasonably be. Wealdstone and South Harrow have more Victorian and Edwardian terraces and, increasingly, flats.
Choosing the right project
On an interwar semi, a loft conversion in Harrow is typically a hip-to-gable with a rear dormer. The side garage that most houses have is a natural candidate for a garage conversion, and a rear or wraparound extension works well on the wider plots. For houses that have not been touched in decades, full refurbishment is often the better value.
Things to check early
Check whether you are in a conservation area or the Green Belt. If you are converting a garage, look at the original planning conditions, because some Harrow estates required parking to stay. Party wall notices apply on semis. We cover each of these in the survey and write the answers into your quote.
What we do in Harrow: Loft conversions in Harrow · House extensions in Harrow · Basement conversions in Harrow · Garage conversions in Harrow · Property refurbishment in Harrow
Worth reading first: Do you need planning permission for a loft conversion? · How to choose the right builder
Nearby: Builders in Barnet · Builders in Wembley
Ready to talk? Book a free site survey and we will tell you in writing which planning route your address needs.
Areas We Cover
Areas We Cover in Harrow
Harrow on the Hill
Pinner
Stanmore
Hatch End
Rayners Lane
North Harrow
Kenton
Wealdstone
Harrow Weald
South Harrow
Don't see your street listed? Our builders in Harrow cover the whole borough and the surrounding area — get in touch to check.
Our Work
Recent Harrow Projects
A look at recent work carried out for clients in and around Harrow.
Mansard Roof Loft Conversion
An under-used loft transformed into three light-filled bedrooms and a family bathroom, with a full mansard roof extension built to Building Control standards from start to finish.
View Project →
Rear Extension — Open-Plan Kitchen & Living Space
A single-storey rear extension that opened up a cramped, closed-off floor plan into one bright, open-plan kitchen and living space.
View Project →What Clients Say
Reviews from Harrow
“Alpha converted our loft into two bedrooms and a bathroom without a single hiccup. They turned up when they said they would, kept the site tidy, and the finish is better than we hoped for.
”
Priya Shah
Loft Conversion, Walthamstow
Common Questions
FAQs About Builders in Harrow
Can I convert my Harrow semi's garage into a room?
Usually, because converting an attached garage is normally an internal change. You will need Building Regulations approval, and you should check the original planning permission for a condition keeping the garage or parking in place. We look this up during the survey.
Does Green Belt land in Harrow mean no extensions?
No, but extensions are judged against the size of the original house, and earlier additions count. A modest extension is often achievable, but the same scheme on a Rayners Lane plot would face less scrutiny. We measure first, then advise.
Do I need planning permission for a hip-to-gable loft in Pinner?
Not always. Outside the Pinner Village conservation area and other designated streets, a hip-to-gable with a rear dormer is usually permitted development if the added volume stays within 50 cubic metres. The front slope cannot be altered in the same way. Building Regulations still apply.
How do I extend a house in Harrow on the Hill?
Carefully. The village centre is a conservation area with many listed buildings, so planning permission is likely, and materials and proportions matter. Rear and side work that is hidden from the street tends to be easier than anything visible from the road.
Ready When You Are
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Free site survey, a fixed-price quote within 48 hours, and one team from first fix to final handover.
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