A single-storey extension is a new ground-floor room built onto your house, usually at the rear or side, with its own foundations, walls and roof, creating a bigger kitchen, living space or bedroom without moving home.
Addresses across WD1, WD2, WD5 and WD17 fall within our coverage for a single-storey extension, so if your home is in North Watford we can arrange a survey on a day that works for you. We inspect the existing building, discuss materials and layout, and then price the agreed specification in writing. Expect a guide range of £37,000–£79,000 including VAT before that visit.
- Guide price
- £37,000–£79,000 inc VAT
- Time on site
- 10–16 weeks on site
- Postcodes
- WD1, WD2, WD5, WD17 and WD24
- Planning rules
- England
- Local area
- Hertfordshire
- Survey
- Free, with a written quote
How much does a single-storey extension cost in North Watford?
The costs listed here are typical for a single-storey extension around North Watford and include VAT. They reflect labour and material costs in the East of England, about 5% above the national guide, giving a range of £37,000–£79,000. Exact pricing depends on your home, so we only fix it once a free site survey is done.
| Type of job | What it usually involves | Guide in North Watford |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £23,000–£42,000 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £37,000–£79,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £74,000–£136,000 |
What moves the price up or down:
- Floor area, shape and number of corners
- Roof type, rooflights, lanterns and the amount of glazing
- Ground conditions, foundation depth and drains to divert
- Finishes, kitchen, flooring and heating specification
What does the job include in North Watford?
- Groundworks, foundations and below-ground drainage
- Cavity walls built and insulated to building regulations
- Flat or pitched roof, with rooflights or a lantern if specified
- Steel beams to open into the existing house
- Windows and external doors, including bifolds if chosen
- Building control inspections and completion certificate
What are homes like around North Watford?
Hertfordshire is home to the first garden cities, Letchworth and Welwyn Garden City, and the post-war new towns of Stevenage, Hatfield and Hemel Hempstead. Watford and St Albans have Victorian terraces and Georgian streets, interwar semis line the commuter suburbs, and brick-and-flint cottages appear in Chiltern villages to the west.
New-town and garden-city homes often suit extensions, window replacement and roofline renewal, though some garden-city estates have their own design guidance. Victorian terraces commonly take loft rooms and side-return extensions.
None of this holds for every street in North Watford, which is why we look at your actual house before pricing a single-storey extension rather than assuming from its age alone.
Planning and building rules in North Watford
Because North Watford falls under England's rules, the guidance below is the version relevant to you. Before sending a price, we check your property's position with the council.
In England, many single-storey rear extensions are permitted development: typically up to 3 m deep on a semi-detached or terraced house and 4 m on a detached house, no more than 4 m high, and covering no more than half the land around the original house. Larger rear extensions can go through the prior approval process. Side extensions, flats, listed buildings, conservation areas and homes where permitted development rights have been removed need planning permission.
Building Regulations approval is needed for almost every extension, covering foundations, structure, insulation, drainage, ventilation and fire safety. If the work is on or near a shared wall or boundary, the Party Wall etc. Act 1996 may apply.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
How does the job run?
Free site survey
We begin by looking at the job in person. During the free survey we discuss options, materials and budget for a single-storey extension, and photograph or measure anything the quote needs to reflect.
Written quote
We turn the survey notes into a written quote. The price is fixed for the specification we agree, and the document sets out materials, scope and payment stages in plain language.
Plan and prepare
Next comes planning the work itself. We set a start date that suits you, line up the right trades, and make sure any approvals for a single-storey extension are in place before the first day on site.
The work itself
The work is carried out to the agreed specification, with floors and furniture protected and the site kept tidy. At the end we clean up, walk through the finished job with you and hand over any certificates.
Working with SK Home Improvements
Common questions
Do I need planning permission in North Watford?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. North Watford is in England, so England's rules apply. Many smaller jobs need no planning application, but some still need building control approval. We check what applies to your address before quoting.
Is the price fixed?
Yes, for the specification we agree. Your written quote sets out exactly what is included at a fixed price. It only changes if you ask for something different, or if a problem the survey could not reasonably reveal later needs extra work. In either case we explain the change and confirm it in writing before going ahead.
What is the Party Wall Act and does it apply to me?
The Party Wall etc. Act 1996 applies in England and Wales only. In England and Wales, it requires you to give notice to neighbours before certain work on or near a shared wall, such as digging foundations within 3m of their building and deeper than its footings. Neighbours can agree or appoint a surveyor. Scotland and Northern Ireland have no equivalent Act, though general rights still apply. We identify whether notices are needed during the survey.
How much does a single-storey extension cost?
A typical single-storey rear extension of 15–25m² costs £37,000–£79,000, built to a plastered finish ready for your kitchen and decoration. As a guide, allow roughly £1,600–£2,800 per square metre plus fixed costs for groundworks, steelwork and fees. Smaller extensions cost more per square metre. The kitchen, flooring and large glazed doors are usually the biggest extras. We confirm a fixed price for the agreed specification after the survey.
Can we stay at home during the build?
Most people stay at home while we build a single-storey extension, because the new structure goes up outside before we break through. The disruptive part is usually the last few weeks, when we open into the house and fit the kitchen. We put up dust screens, keep a safe route through the house and agree a temporary kitchen setup if needed. Water and power are only off for short, planned periods.
Near North Watford
If your address falls within WD1, WD2, WD5 and WD17, we cover it. The same goes for neighbouring Watford, Bushey and Rickmansworth, which we include alongside North Watford when arranging surveys and quotes.