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 Kilwinning?
In Kilwinning, 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. Prices in Scotland sit near the national average for this kind of work, and the range for Kilwinning reflects that. 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
- Waterproofing system
- Floor lowering and underpinning
- Lightwells
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 basement conversion in Kilwinning?
Before anything is built in Kilwinning, we confirm which approvals apply 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.
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.
We check this for your address before design work starts, so there are no surprises later.
What we handle
What we take care of:
- Written agreement with neighbours on shared walls
- Lightwells and windows
- Insulation, ventilation and drainage pumps
- Structural and ground survey
- Building control sign-off
- Waterproofing design (tanking or cavity drain membrane)
How long does it take?
Build time is typically 8 to 16 weeks for a cellar conversion; longer for new excavation. Allow time beforehand for drawings and approvals, usually 3 to 5 months.
Building in Kilwinning
In Scotland, bungalows and one-and-a-half-storey homes are common, so dormer conversions are a popular way to add bedrooms.
We work across Kilwinning and neighbouring areas such as Irvine, Saltcoats and Troon. Postcodes we cover in Kilwinning include KA13.
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
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about basement conversions in Kilwinning
Can a basement be a bedroom?
Yes, with a suitable escape route such as a lightwell window or protected stair.
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 Kilwinning?
Planning matters in Kilwinning go to the council covering your address, and the work needs a building warrant. We prepare and submit the applications for you.
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 Kilwinning?
In Kilwinning, 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.
Do I need planning permission for a basement conversion in Kilwinning?
In Scotland converting an existing cellar may not need planning permission, but a building warrant is needed, and new excavation usually needs planning permission.