House Extension Costs in Poole & Bournemouth: 2025 Guide
A house extension is one of the most popular home improvement projects in Poole and Bournemouth — and with good reason. A well-designed extension adds significant living space, increases property value, and avoids the cost and disruption of moving. This guide covers realistic costs, planning requirements, and what to expect when extending your home in Dorset.
Types of House Extension
Single-Storey Rear Extension
The most common type of extension in Poole and Bournemouth. A single-storey rear extension typically creates an open-plan kitchen-diner, a larger living room, or a garden room. Popular features include bi-fold doors, lantern roof lights, and underfloor heating.
Typical cost in Dorset: £35,000–£65,000 depending on size and specification.
Double-Storey Extension
A double-storey extension adds space on both the ground and first floor — often a kitchen-diner below and a bedroom or bathroom above. More cost-effective per square metre than a single-storey extension.
Typical cost in Dorset: £60,000–£120,000+
Side Return Extension
Fills in the narrow side passage typical of Victorian and Edwardian terraced houses. Often combined with a rear extension for an L-shaped layout.
Typical cost in Dorset: £30,000–£55,000
Wrap-Around Extension
Combines a rear and side return extension to maximise ground-floor space. Creates a dramatic transformation of the ground floor layout.
Typical cost in Dorset: £65,000–£130,000+
What Affects the Cost of a House Extension in Poole?
- Size — cost per square metre typically ranges from £2,000–£3,500 in Dorset depending on specification
- Specification — bi-fold doors, lantern roof lights, underfloor heating, and high-end kitchen finishes add significant cost
- Groundworks — poor ground conditions, drainage diversions, or proximity to trees can increase foundation costs
- Structural complexity — removing load-bearing walls, installing RSJ beams, and creating open-plan layouts add cost
- Finishes — plastering, flooring, decorating, and kitchen or bathroom fitting are often priced separately
Do You Need Planning Permission for a House Extension in Poole?
Many single-storey rear extensions in Poole and Bournemouth fall under Permitted Development rights and do not require planning permission, provided:
- The extension does not exceed 4 metres deep for a detached house (3 metres for semi-detached or terraced)
- Under the Neighbour Consultation Scheme, these limits extend to 8 metres (detached) and 6 metres (semi/terraced)
- The extension does not exceed 4 metres in height
- The extension does not cover more than half the garden area
- Materials match the existing house
Two-storey extensions, side extensions, and extensions in conservation areas or Areas of Outstanding Natural Beauty require full planning permission.
We recommend applying for a Lawful Development Certificate even for Permitted Development extensions — this provides legal confirmation that the extension is lawful and protects you when selling the property.
How Long Does a House Extension Take?
A single-storey rear extension typically takes 8–14 weeks from groundworks to completion. A double-storey extension may take 16–24 weeks. We provide a detailed project timeline before work begins.
The Ross-Read Building Process
1. Free consultation — we visit your property, discuss your vision, and advise on planning and design options
2. Detailed written quote — itemised, fixed-price quote with a clear project timeline
3. Planning and Building Regulations — we manage the full process, including liaison with architects and structural engineers
4. Build and handover — our team carries out all works to the highest standard, keeping you informed throughout
Call 01202 818288 or [request a free quote](/contact) to start planning your extension.