What is a basement conversion?
A basement conversion turns an existing cellar into living space, or excavates a new basement under the house or garden. Waterproofing, structural support and daylight are the main design challenges.
How much does a basement conversion cost in Perth?
In Perth, a basement conversion typically costs £1,850–£3,100 per m² for converting an existing cellar, including VAT at 20% (standard rate). For a typical 30 m² project that is roughly £55,500–£93,000. 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 (21 m²) | £39,000–£65,000 |
| Typical project (30 m²) | £55,500–£93,000 |
| Larger project (42 m²) | £77,500–£130,000 |
| Rate per m² | £1,850–£3,100 |
What moves the price most:
- Agreements with neighbours on shared walls
- Existing cellar or new excavation
- Ground water and access
- Lightwells
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a basement conversion in Perth?
The approval route for Perth is set by planning law in Scotland. In Scotland converting an existing cellar may not need planning permission, but a building warrant is needed, and new excavation usually needs planning permission.
In Scotland a building warrant is needed before work starts on most extensions, loft conversions and conversions. It is issued by the council’s building standards service. When the work is finished, a completion certificate is submitted and accepted by the council after inspection.
We check this for your address before design work starts, so there are no surprises later.
What we handle
What we take care of:
- Structural and ground survey
- Underpinning or new structure where needed
- Waterproofing design (tanking or cavity drain membrane)
- Written agreement with neighbours on shared walls
- Insulation, ventilation and drainage pumps
- Lightwells and windows
How long does it take?
The build itself usually takes 8 to 16 weeks for a cellar conversion; longer for new excavation. Design and approvals come first and typically take 3 to 5 months, depending on the approval route.
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.
From PH1 outwards, we take on projects throughout Perth and the surrounding parts of Tayside.
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
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about basement conversions in Perth
Can a basement be a bedroom?
Yes, with a suitable escape route such as a lightwell window or protected stair.
Do I need planning permission for a basement conversion in Perth?
In Scotland converting an existing cellar may not need planning permission, but a building warrant is needed, and new excavation usually needs planning permission.
How long does it take?
A cellar conversion takes around 8 to 16 weeks; new basements take longer.
How much does a basement conversion cost in Perth?
In Perth, a basement conversion typically costs £1,850–£3,100 per m² for converting an existing cellar, including VAT at 20% (standard rate). A typical 30 m² project comes to roughly £55,500–£93,000. Your fixed price depends on the survey and drawings.
How do you keep a basement dry?
With a waterproofing system designed to BS 8102, typically a cavity drain membrane with a sump pump, or a tanking system.
Who approves a basement conversion in Perth?
Planning matters in Perth go to the council covering your address, and the work needs a building warrant. We prepare and submit the applications for you.