A double-storey extension adds two floors of new space to your house in one build, typically a larger kitchen or living room downstairs with an extra bedroom, bathroom or en-suite above, sharing one set of foundations and one roof.
Thinking about a double-storey extension in Frome? We take charge of the whole project, co-ordinating every trade involved, and one person keeps you updated. Guide prices for the South West sit at £61,000–£122,000 including VAT, and a typical job takes 14–22 weeks on site. Your own figure depends on what the survey finds and the specification you settle on.
- Guide price
- £61,000–£122,000 inc VAT
- Time on site
- 14–22 weeks on site
- Postcodes
- BA11
- Planning rules
- England
- Local area
- Somerset
- Survey
- Free, with a written quote
Double-storey extensions prices in Frome
Prices for a double-storey extension vary from house to house, but in Frome most projects fall within £61,000–£122,000 including VAT. That reflects costs in the South West, about 2% above the national guide. Treat the table as a budgeting aid; the written figure follows a survey we carry out for free.
| Type of job | What it usually involves | Guide in Frome |
|---|---|---|
| Small (15–20m² total) | A compact rear or side extension adding a small room on each floor. | £41,000–£66,000 |
| Typical (30–40m² total) | A larger kitchen or living room below with a double bedroom or en-suite above. | £61,000–£122,000 |
| Large (50m² plus total) | Wide or deep extensions, often with a new bathroom, steelwork and high-spec glazing. | £102,000–£184,000 |
Expect these to shape the final quote:
- Combined floor area across both storeys
- How the new roof joins the existing roof
- Bathrooms, en-suites and plumbing on the upper floor
- Foundation depth, ground conditions and drains to divert
What’s included?
- Groundworks, foundations and below-ground drainage
- First-floor joists, stud walls and new openings upstairs
- Scaffolding for the full build, erected and inspected
- Electrics, plumbing and heating by qualified trades, with certificates
- Windows, external doors, plastering and internal doors
- Building control inspections and completion certificate
Homes in Somerset
Somerset's building stone varies widely: Bath stone in Bath, golden Ham stone around Yeovil, blue lias in villages on the Levels and Mendip stone in the north. Weston-super-Mare has Victorian villas and terraces, Taunton and Bridgwater have brick terraces and post-war estates, and new housing continues to spread around the larger towns.
Stone properties often need lime pointing, stone repairs and windows that respect conservation areas, especially in Bath. Brick terraces suit loft rooms and extensions, and estate homes commonly take garage conversions.
These patterns matter for a double-storey extension: older walls, roofs and floors in Frome can need different materials or extra preparation compared with newer homes.
Permissions for a double-storey extension in Frome
For anyone in Frome, the relevant framework is England's. The summary below is general, so we always contact the council about your address before putting a price in writing.
In England, a two-storey rear extension can only be permitted development if it is no more than 3 m deep, at least 7 m from the rear boundary and finished to match the house. Most double-storey and all two-storey side extensions need full planning permission.
Building Regulations approval is needed, with structural calculations for beams, foundations and the roof. The Party Wall etc. Act 1996 often applies on semi-detached and terraced houses.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
The four stages
A visit to your home
A free survey comes first. It gives us what we need to price a double-storey extension properly, including dimensions, existing materials and access for deliveries, and gives you the chance to ask anything you like.
Your fixed price
After the survey we send a quote for a double-storey extension that fixes the price for the scope we've agreed. If you want to change materials or scope, we revise it in writing before anything is booked.
Getting ready
We handle the paperwork side: checking whether planning permission or building control approval is needed, submitting applications where they are, and scheduling the trades and materials around your dates.
On site to finish
Work goes ahead as scheduled and you deal with one contact throughout. When the last trade leaves, we clear and clean the site, talk you through what has been done and pass on any certificates and care instructions.
How we work
Common questions
Do you cover Trowbridge, Bath and Melksham?
Yes. As well as Frome, we cover Trowbridge, Bath and Melksham and the rest of Somerset. Our coverage is UK-wide, so the process is the same wherever you are: a free site survey, a quote in writing that fixes the price for the agreed scope, and one point of contact while the work is planned and carried out.
How is the new roof joined to the existing house?
The new roof is usually tied into the existing roof so the two read as one. On a rear extension this often means a lower ridge or a hipped end, with valleys where the slopes meet. We strip back some existing tiles, fix new rafters and battens, and lay matching tiles or slates. Lead or proprietary flashings seal the junctions so water runs off properly.
How long does a double-storey extension take?
A double-storey extension typically takes 14–22 weeks on site, depending on size, roof design and weather. Foundations and ground-floor walls come first, then the first-floor joists, upper walls and roof. Once it is weathertight, electrics, plumbing, plastering and finishes follow. Allow extra time beforehand for drawings, calculations and approvals. We give you a stage-by-stage programme with your quote.
How much does a double-storey extension cost?
A typical double-storey extension of 30–40m² across both floors costs £61,000–£122,000, built to a plastered finish. As a rough guide, allow around £1,400–£2,600 per square metre plus fixed costs for groundworks, scaffolding and fees. The second storey usually costs less per square metre than the first, because foundations and roof are shared. Bathrooms upstairs and a complex roof add most. We confirm a fixed price after the survey.
Do I need planning permission in Frome?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. Frome 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.
Nearby towns
From BA11 to the edges of Frome and on into Trowbridge, Bath and Melksham, we can arrange a site visit and a written quote for your project, planned around dates that work for you.