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.
In Merthyr Tydfil, as anywhere in Mid Glamorgan, the price of a single-storey extension is driven mainly by size, materials and access. Across Wales our guide sits at £32,000–£69,000 with VAT, but restricted parking, a narrow side passage or extra preparation can move the figure either way. That is why every price we give follows a visit to the house.
- Guide price
- £32,000–£69,000 inc VAT
- Time on site
- 10–16 weeks on site
- Postcodes
- CF47 and CF48
- Planning rules
- Wales
- Local area
- Mid Glamorgan
- Survey
- Free, with a written quote
What should you budget for a single-storey extension in Merthyr Tydfil?
Use the table to gauge the cost of a single-storey extension in Merthyr Tydfil before we visit. Figures include VAT and are scaled for Wales, coming out about 8% below the national guide, which gives £32,000–£69,000 overall. After a free survey, you receive a fixed written price.
| Type of job | What it usually involves | Guide in Merthyr Tydfil |
|---|---|---|
| Small extension (8–12m²) | A modest rear or side extension, such as a utility room or a slightly larger kitchen. | £20,000–£37,000 |
| Typical rear extension (15–25m²) | A kitchen-diner or family room with bifold doors and a rooflight or lantern. | £32,000–£69,000 |
| Large or wrap-around (30m² plus) | A wrap-around or wide rear extension, often with structural steelwork into the house. | £64,000–£120,000 |
Your price depends mostly on:
- Floor area, shape and number of corners
- Roof type, rooflights, lanterns and the amount of glazing
- Ground conditions, foundation depth and drains to divert
- Steelwork needed to open into the existing house
Scope of the work
- 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
- Electrics and plumbing by qualified trades, with certificates
- Windows and external doors, including bifolds if chosen
- Building control inspections and completion certificate
Local housing and a single-storey extension
The Rhondda, Cynon and Merthyr valleys are lined with stone terraces built for mining families, stepped along steep hillsides. Pontypridd, Caerphilly and Merthyr Tydfil have Victorian centres, and Bridgend has grown with large modern estates alongside interwar and post-war housing.
Valley terraces commonly need repointing, roof repairs, rendering and window replacement, and loft conversions can add useful space. Newer estate homes often take garage conversions, porches and landscaping.
In Merthyr Tydfil, as elsewhere in Mid Glamorgan, we take the building's age and construction into account before recommending anything, because both can change what is involved in a single-storey extension.
Do you need permission in Merthyr Tydfil?
England, Wales, Scotland and Northern Ireland each handle planning a little differently. Merthyr Tydfil comes under Wales, covered below, and we raise any questions with the council before your quote is finalised.
In Wales, permitted development allows many single-storey rear extensions, with depth and height limits that depend on the type of house and how close the extension comes to your boundaries. Side extensions, listed buildings, conservation areas and flats usually need planning permission.
Building Regulations in Wales apply to extensions, from foundations to insulation and fire safety. The Party Wall etc. Act 1996 applies in Wales as it does in England.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
The four stages
Survey and measure
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.
Price and scope agreed
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.
Getting ready
With the quote agreed, we book the work in and handle preparation: permissions where needed, building control notifications, material orders and access arrangements for your Merthyr Tydfil property.
Build and hand over
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.
Working with SK Home Improvements
Frequently asked questions
Can you combine a single-storey extension with other work?
Yes. Because we manage several trades under one contract, we can plan a single-storey extension alongside other work on your Merthyr Tydfil home, such as new windows with rendering, or a kitchen refit with an extension. Combining jobs can reduce repeat set-up such as scaffolding, skips and access, and every element is listed and priced in the same written quote.
Is a flat roof or a pitched roof better on an extension?
A flat roof is quicker to build and usually costs less, gives a clean modern look and works well with a roof lantern. A pitched roof matches the main house, sheds water faster and allows a vaulted ceiling, but it costs more and its height can affect neighbours. Modern flat roofs in EPDM rubber or GRP last well when properly detailed. Planning rules on height can also decide the choice.
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.
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.
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 Merthyr Tydfil
Live in Merthyr Tydfil? Our coverage takes in the CF47 and CF48 postcode areas and reaches out to Aberdare, Rhondda and Ebbw Vale, so homes on the outskirts and in the next town along are included.