Straight answers to the questions people ask before they build

We are based in Hendon, NW4, and work across North London and south Hertfordshire: Finchley, Mill Hill, Totteridge and Whetstone, Barnet, Hampstead Garden Suburb, Highgate and Muswell Hill, Edgware and Stanmore, Harrow, Enfield, Radlett and Bushey, plus neighbouring areas by arrangement. Projects further afield are considered case by case.

Most of our work is in the £50,000 to £500,000 range: single-storey and double-storey extensions, loft and basement conversions, whole-house refurbishments and new-build houses. We do not take on small repair jobs, single-room decorating or kitchen-only replacements unless they are part of a larger project.

Yes. Our design team takes projects from feasibility sketches through planning and Building Regulations drawings to the technical detail the site team builds from. If you already have an architect we are equally happy to price and build from their drawings.

Yes. We check whether the work falls under permitted development, prepare and submit planning or prior-approval applications where needed, apply for lawful development certificates, and manage the Building Regulations application and inspections with the local authority or an approved inspector.

As a 2026 market guide, single-storey extensions in North London typically fall between £2,800 and £4,500 per square metre for the shell and basic finish, so a 25 m² rear extension is commonly £75,000 to £115,000 plus VAT, kitchen and professional fees. Site conditions, glazing, structure and specification move the figure considerably; we give a proper estimate after a site visit.

Design and approvals usually take three to five months before work starts (planning applications alone take eight weeks once validated). On site, a single-storey extension takes around 10 to 16 weeks, a loft conversion 8 to 12 weeks, a whole-house refurbishment three to six months, and a new house nine to fourteen months. We agree a programme before starting.

Often, yes — loft conversions and rear extensions can usually be done with you in the house, sealed off from the work. Whole-house refurbishments with rewiring, new plumbing and structural changes are quicker, cheaper and far less stressful if the house is empty. We will tell you honestly which applies.

We carry public and employer's liability insurance and can provide certificates on request. Warranty terms are agreed in the contract for each project and confirmed in writing before work starts.

Work is carried out under a written contract with a fixed contract sum, and payments are made in stages against completed work — never large sums up front. Any changes you ask for during the build are priced and agreed in writing before they are carried out.

Stoyan reads it and replies within one working day. We then have a short call about the property, brief and budget, and if it is a good fit we arrange a site visit, usually within a week, followed by a written proposal. There is no charge and no obligation for any of this.

A design and build company designs a building project, obtains the approvals and constructs it under one contract, so the client has a single point of responsibility for design, cost and quality. Milkov & Son provides feasibility, architectural design, planning and Building Regulations submissions and construction in North London.

It is usually cheaper overall, mainly because cost is tested at feasibility rather than discovered at tender, and because buildability problems are designed out rather than charged as variations. Design fees themselves are similar; the savings are in fewer surprises.

Not with the right company. Our design team produces planning and technical drawings to the same standard, and you are welcome to appoint an independent architect for concept design and have us develop and build it. What you gain is a design that has been priced and checked for buildability from the start.

As a market guide, £2,800 to £4,500 per square metre for the build, so a typical 25 m² single-storey rear extension is £70,000 to £130,000 before VAT, professional fees and the kitchen. Double-storey extensions of 40–60 m² typically run £120,000 to £220,000. Figures depend heavily on structure, glazing, ground conditions and finishes.

Allow three to five months for design and approvals, then 10 to 16 weeks on site for a single-storey extension and 14 to 24 weeks for a double storey. A whole project from first meeting to finished room is commonly seven to twelve months.

Often, if you live in a house (not a flat) outside an Article 4 area: single-storey rear extensions up to 3 m (terraced/semi) or 4 m (detached), or 6 m/8 m with prior approval, within height and coverage limits. Wraparounds, most double-storey extensions and anything in a restricted area need a planning application.

As a 2026 guide, £1,200 to £1,800 per square metre for a mid-range full renovation and £1,800 to £2,500 or more for high specification, so a typical 110 m² three-bedroom house is £130,000 to £200,000 plus VAT and fees. Light refurbishment without structural or services work is £800 to £1,200 per square metre.

Typically 12 to 18 weeks on site for a three-bedroom house and five to eight months for a large house with structural changes, after six to ten weeks of survey, design and specification.

Not for internal work, unless the building is listed. External changes such as new front windows, render, a porch or roof alterations may need permission in conservation areas or where an Article 4 direction applies. Building Regulations approval is needed for structural, electrical, drainage, glazing and thermal work regardless.

Usually not, if the house is not a flat, is not in a conservation area or Article 4 street, and the enlargement is within 40 m³ (terraced) or 50 m³ (other houses) with no dormer facing the road and no part above the ridge. Mansards, L-shaped dormers beyond the volume limit, front dormers and anything in a designated area need a householder application.

In 2026, roughly £30,000 to £45,000 for a rooflight conversion, £50,000 to £75,000 for a rear dormer, £65,000 to £95,000 for a hip-to-gable with dormer and £80,000 to £130,000 or more for a mansard, excluding VAT.

Eight to twelve weeks on site, after three to six weeks of design and the eight-week certificate or planning period. Most families stay in the house throughout.

In 2026, converting an existing cellar costs around £2,800 to £4,200 per square metre, lowering a floor £4,000 to £5,500, and excavating a new basement £4,800 to £6,500 or more, all excluding VAT, fees and fit-out. A 40 m² new basement under a terrace is typically £220,000 to £320,000.

Converting an existing cellar without external changes usually does not. New basements, substantial floor lowering, light wells and external stairs generally need a planning application, and several North London boroughs have specific basement policies and require a Basement Impact Assessment.

By a waterproofing system designed to BS 8102, usually a Type C cavity-drain membrane with a sump and pumps, often combined with a second form of protection. It is designed by a waterproofing specialist and installed with an insurance-backed guarantee.

As a 2026 market guide, £2,400 to £3,300 per square metre of construction for a good-quality family house in outer North London and Hertfordshire, and £3,300 to £4,500 or more for high specification, excluding land, fees and CIL. A 180 m² four-bedroom house is typically £450,000 to £600,000 to construct.

Construction of a qualifying new dwelling is zero-rated for VAT, so the builder's charges for the build itself carry no VAT. Professional fees, and some works to existing buildings retained on the site, are standard-rated.

Around 18 to 24 months from first meeting to moving in: six to ten weeks of feasibility, four to six months for planning, two to three months of technical design, then nine to fourteen months on site.

You need drawings prepared by someone competent: for planning, Building Regulations and for the builder to price. That can be a chartered architect, an architectural technologist or a design-and-build company's design team. Our guide 'Do I need an architect for a home extension or renovation?' sets out when an independent architect adds value.

Yes. Design stages are charged at fixed fees and the drawings are yours. Many clients ask us to price the build as well, but there is no obligation.

Eight weeks from the date the council validates a householder application, plus the time to prepare the drawings (three to five weeks). Prior approval takes 42 days; a Lawful Development Certificate eight weeks.

Our interior design service is delivered as part of Milkov & Son projects — extensions, renovations and new homes — so that design and delivery sit with one team. We do not currently offer stand-alone decoration or styling.

Yes. We regularly deliver schemes designed by independent interior designers and will coordinate first-fix drawings, samples and specialist suppliers with them.

Before technical design is finished, and certainly before the drainage and electrical first fix. We give a decisions calendar at the start of the project with dates for every choice.