Two-storey rear extensions in Treharris
Adding a two-storey rear extension in Treharris gives you two new rooms stacked on one footprint. Here's how we'd approach it, what it typically costs and the rules that apply in Wales.
Before you start in Treharris, here's what applies.
- Postcode districts
- CF46
- County / area
- Mid Glamorgan, Wales
- Price region
- Wales
- Guide price
- £51,500–£69,500 (£1,840–£2,480 per m²)
- Approval route
- It may be permitted development if the ground floor goes no more than 4 m and the first floor no more than 3 m beyond the original rear wall, with the first floor 10.5 m from the rear boundary.
- Nearest towns
- Nelson (Mid Glamorgan) (1.2 miles), Abercynon (1.6 miles), Gelligaer (2.2 miles)
- Distance to Rhondda
- about 6.1 miles
- First visit
- Free, no obligation
About a two-storey rear extension
A two-storey rear extension suits you if you need more room on both floors and have a reasonably deep garden. You get one team for the whole job: a measured survey, the design, a check on whether permitted development applies, planning drawings where they are needed, structural design, building regulations approval and the build itself, carried out by vetted teams working under S&K. Every project starts with a free site visit.
We cover postcode district CF46 in and around Treharris, along with neighbouring Nelson (Mid Glamorgan), Abercynon and Gelligaer.
What it costs in Treharris
A guide price for Treharris: around £51,500–£69,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). That works out at £1,840–£2,480 per m² of new floor space, including VAT at 20%. We'll give you a written design-stage price first, then a fixed build price once the drawings are agreed.
| Spec | Per m² | A 4 m × 3.5 m footprint on two floors (28 m² of new floor space) |
|---|---|---|
| Essential | £1,690–£2,290 per m² | £47,500–£64,000 |
| Standard | £1,840–£2,480 per m² | £51,500–£69,500 |
| Premium | £2,210–£2,980 per m² | £62,000–£83,500 |
Planning and building regulations in Treharris
In Wales, a two-storey rear extension can be permitted development if the ground floor goes no more than 4 m and the first floor no more than 3 m beyond the original rear wall, with the first floor at least 10.5 m from the rear boundary. Nothing within 2 m of a boundary can be higher than 4 m. Conservation areas and other protected areas are excluded, and a householder application costs £585.
Approval in Wales: Householder planning application: £585. Councils normally decide householder applications within 8 weeks.
Building regulations: Building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency).
Design points for Treharris homes
Opening up the ground floor
Knocking through the old rear wall means steel beams to carry the first floor and roof above. The structural engineer sets the beam sizes, padstones and any posts, and we plan them early so the open-plan layout you want is the one that gets built.
Upstairs layout and windows
Bedrooms above need a window big enough for escape or a protected route to the stairs. Side-facing upstairs windows normally have to be obscure-glazed and fixed below 1.7 m, so we put the main bedroom windows in the rear wall and use roof lights where extra daylight is needed.
How we'd run your project
Visit and first ideas
One of our team visits your house in Treharris, checks the walls, roof and drains, and sketches out options with you.
Get it approved
Once you're happy with the design we submit it to the council for Treharris and deal with any questions from the planning officer.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.
Questions about two-storey rear extensions in Treharris
Which postcodes do you cover around Treharris?
We cover Treharris (CF46) and nearby places including Nelson (Mid Glamorgan), Abercynon and Gelligaer, plus the rest of Mid Glamorgan. The first site visit is free.
How much does a two-storey rear extension cost in Treharris?
Our guide for Wales, which covers Treharris, is £1,840–£2,480 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £51,500–£69,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Do I need planning permission for a two-storey rear extension in Treharris?
Treharris is in Wales, so Wales planning rules apply. It may be permitted development if the ground floor goes no more than 4 m and the first floor no more than 3 m beyond the original rear wall, with the first floor 10.5 m from the rear boundary. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.
Who handles building regulations for a project in Treharris?
We handle it as part of the project. What's needed in Wales: building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency). We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
Will a two-storey rear extension block my neighbour's light?
It can if it is too deep or too close to the boundary, which is why councils look closely at its effect on neighbouring windows and gardens. We test the design against light and outlook early, keep the first floor shorter or set in where needed, and use a hipped roof to reduce bulk on the boundary side.
Nearby
The same service in neighbouring towns:
Other extensions in Treharris
- Side
- Wraparound
- Part two-storey
- Over a garage
- First floor
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Treharris · Two-storey rear extensions across Mid Glamorgan
Ready to talk it through? Call us or send the form and we'll arrange a visit to your home in Treharris.