What is a side extension?
A side extension builds into the space beside a semi-detached or detached house, often over a driveway or side passage. It can be single-storey, for a utility room, downstairs toilet or study, or two-storey to add a bedroom above.
How much does a side extension cost in Mid Glamorgan?
In Mid Glamorgan, a side extension typically costs £1,550–£2,450 per m² of floor area, including VAT at 20% (standard rate). For a typical 28 m² project that is roughly £43,500–£68,500. Building costs in Wales run about 8% below the UK average, and the figures for Mid Glamorgan are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (20 m²) | £31,000–£49,000 |
| Typical project (28 m²) | £43,500–£68,500 |
| Larger project (39 m²) | £60,500–£95,500 |
| Rate per m² | £1,550–£2,450 |
The main things that change the cost:
- Steel work where the side wall is opened
- Internal fit-out of the new rooms
- Roof design and tile matching
- Drains, gas meters or soil pipes that need moving
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a side extension in Mid Glamorgan?
Approvals for a side extension in Mid Glamorgan follow the rules for Wales. In Wales a single-storey side extension can be permitted development if it is no more than 4 metres high and the widest part of the house ends up no more than 50% wider than the original. Two-storey side extensions must be at least 10.5 metres from the side boundary and set back 1 metre from the front, so most need planning permission. In conservation areas single-storey side extensions are limited to 3 metres.
Building regulations in Wales are set by the Welsh Government. Approval comes from the council’s building control service or a registered building control approver, with inspections during the work and a completion certificate at the end.
We check this for your address before design work starts, so there are no surprises later.
What we handle
From survey to sign-off, the job normally involves:
- Survey of the boundary, drains and access
- Electrics, heating and plastering
- Walls, roof and windows to match the house
- Foundations and drainage alterations
- Planning drawings and application
- Structural calculations
How long does it take?
The build itself usually takes 10 to 16 weeks on site depending on size and storeys. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in Mid Glamorgan
Terraced houses in Welsh towns often have narrow plots, which suits rear and side return extensions and rear dormers.
Towns we cover in Mid Glamorgan include Bridgend, Merthyr Tydfil, Pontypridd, Aberdare, Caerphilly and Maesteg.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about side extensions in Mid Glamorgan
Can a side extension go over a drain?
Often yes, with a build-over agreement from the water company or by rerouting the drain. We check this during the survey.
How long does a side extension take in Mid Glamorgan?
Typically 10 to 16 weeks on site depending on size and storeys. Design and approvals beforehand usually take 3 to 4 months.
Will a two-storey side extension look odd?
Not if it is designed well. Setting it back from the front and keeping the roof lower than the main ridge usually gives a natural look and is what most councils ask for.
How close to the boundary can I build?
You can build up to the boundary, but the eaves height near it is limited under permitted development, and planning officers often want a gap at first floor. If you build on or near a shared boundary, party wall rules may apply.
Do I need planning permission for a side extension in Mid Glamorgan?
In Wales a single-storey side extension can be permitted development if it is no more than 4 metres high and the widest part of the house ends up no more than 50% wider than the original. Two-storey side extensions must be at least 10.5 metres from the side boundary and set back 1 metre from the front, so most need planning permission. In conservation areas single-storey side extensions are limited to 3 metres.
How much does a side extension cost in Mid Glamorgan?
In Mid Glamorgan, a side extension typically costs £1,550–£2,450 per m² of floor area, including VAT at 20% (standard rate). A typical 28 m² project comes to roughly £43,500–£68,500. Your fixed price depends on the survey and drawings.