What is a single-storey extension?
A single-storey extension is a ground-floor addition, usually at the rear of a house, that enlarges a kitchen, living or dining space. Most are built with cavity walls on concrete foundations and finished with a flat roof and roof lantern or a pitched tiled roof.
How much does a single-storey extension cost in Perth?
In Perth, a single-storey extension typically costs £1,900–£2,800 per m² of floor area, including VAT at 20% (standard rate). For a typical 20 m² project that is roughly £38,000–£56,000. Building costs in Scotland are close to the UK average, so the figures for Perth are close to our national guide. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (14 m²) | £26,500–£39,000 |
| Typical project (20 m²) | £38,000–£56,000 |
| Larger project (28 m²) | £53,000–£78,500 |
| Rate per m² | £1,900–£2,800 |
What moves the price most:
- Kitchen, flooring and finishes, which we can include or leave to you
- Roof type and the size of any lantern or roof windows
- Floor area and the length of new wall
- How much of the existing house is opened up
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a single-storey extension in Perth?
Here is how the rules work for a single-storey extension in Scotland. In Scotland a single-storey extension is often permitted development (Class 1A): where any part is within 1 metre of a boundary, it can project up to 3 metres from the rear wall of a terraced house or 4 metres on other houses, with eaves no higher than 3 metres, an overall height of 4 metres and no more than half the front or rear garden covered. The rights do not apply in conservation areas or to flats, and a building warrant will usually still be needed before work starts.
Scotland has no Party Wall Act. Work on shared walls is governed by your title deeds, the Tenements (Scotland) Act 2004 for flats, and common law, so we agree arrangements with neighbours in writing before work starts.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
On a typical single-storey extension we handle:
- Knock-through to the existing house with steel beams
- Measured survey and design drawings
- Doors, windows and roof glazing installed
- Building control inspections and completion certificate
- Cavity walls, insulation and roof to current building regulations
- First and second fix electrics, heating and plastering
How long does it take?
Build time is typically 10 to 14 weeks on site for a typical rear extension, after approvals. Before that, surveys, drawings and approvals usually take 6 to 12 weeks, longer if the council asks for changes.
Building in Perth
Scotland’s housing ranges from sandstone tenements and villas to post-war and modern estates, and the building warrant system shapes how projects are planned.
Projects in Perth (PH1) are surveyed in person before we quote, so the price reflects your actual property.
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 single-storey extensions in Perth
Do I need planning permission for a single-storey extension in Perth?
In Scotland a single-storey extension is often permitted development (Class 1A): where any part is within 1 metre of a boundary, it can project up to 3 metres from the rear wall of a terraced house or 4 metres on other houses, with eaves no higher than 3 metres, an overall height of 4 metres and no more than half the front or rear garden covered. The rights do not apply in conservation areas or to flats, and a building warrant will usually still be needed before work starts.
How much does a single-storey extension cost in Perth?
In Perth, a single-storey extension typically costs £1,900–£2,800 per m² of floor area, including VAT at 20% (standard rate). A typical 20 m² project comes to roughly £38,000–£56,000. Your fixed price depends on the survey and drawings.
What is a build-over agreement?
If a public sewer runs within 3 metres of the extension, the water company normally has to agree to the work before it starts. We check sewer records during design and apply where needed.
Is VAT charged on an extension?
Yes. Building work on an existing home is standard-rated, so VAT at 20% applies. Our guide prices include it.
Can I stay in the house during the build?
Usually yes. We build the shell before opening up the back wall, so the house stays weathertight for most of the job. There will be a few weeks when the kitchen or back room is out of use.
How long does a single-storey extension take in Perth?
Typically 10 to 14 weeks on site for a typical rear extension, after approvals. Design and approvals beforehand usually take 6 to 12 weeks.