Single storey · Trowbridge
Hilperton Road · 32m² rear
Open-plan kitchen/dining extension with bi-fold doors and roof lantern. Permitted development, 11 weeks on site.
Single, double, wraparound & side.
A house extension is the single biggest decision most homeowners make about their property. Bigger than a kitchen, bigger than a loft. Get it wrong and you live with the regret for a decade; get it right and the house transforms.
We've built every kind of extension in this part of Wiltshire and Somerset — from a 4m square office room behind a 1970s semi in Melksham, to a 110m² wraparound on a Georgian listed building near Bath. The core categories:
Single-storey rear extensions
The most common project we run. Typically used to enlarge a kitchen, create an open-plan living area, or add a utility/boot room. Often qualify under permitted development (PD) if you stay within size limits. Average build time: 10–14 weeks on site.
Double-storey extensions
Adds an extra bedroom or bathroom upstairs alongside the kitchen extension below. Almost always requires full planning permission. Foundation work is more involved (deeper trenches, pad foundations) and the roof tie-in is the most technically demanding part. Average build time: 16–22 weeks.
Wraparound extensions
Combines a rear and side extension into an L-shape. Massively transforms the layout and natural light, but the planning argument is harder — especially in conservation areas. We'll be honest with you about likelihood before drawings start.
Side extensions
Filling in side return space (common in Victorian terraces) or extending out to a side boundary. Often sub-3m and can stay within PD. Loved for the way they fix the awkward narrow kitchen most older houses have.
Planning permission & permitted development.
This is where most projects either fly or fail. Different councils interpret the rules differently, and the rules themselves change. Our quick reference for 2026:
- Wiltshire Council — pragmatic. Most PD applications go through cleanly if drawings are accurate. We submit certificates of lawfulness routinely.
- Bath & North East Somerset (B&NES) — much stricter, especially in the World Heritage Site. Stone matching, scale and rooflines are scrutinised. Allow extra time.
- Mendip District (Somerset Council) — generally reasonable but conservation areas in Frome and Shepton Mallet are tightly controlled.
- Listed buildings — full Listed Building Consent is mandatory, in addition to planning. Materials are specified by the Conservation Officer; expect lime mortar, salvaged stone or matched brick.
If you're not sure which route applies, start with us: a 30-minute conversation usually clarifies whether your project is PD, full planning or a non-starter — before you spend money on drawings.
Our build sequence.
Every extension we run follows the same six phases. Knowing the order helps you plan furniture moves and school holidays.
- Phase 1 — Site visit & quote (week 0). Free, no obligation, we measure up and put a fixed price in writing within 5 working days.
- Phase 2 — Drawings & planning (weeks 1–8). Architectural drawings, planning submission if needed, structural calcs.
- Phase 3 — Foundations (weeks 1–2 on site). Strip footings to building-control depth, building-control inspection at base.
- Phase 4 — Shell (weeks 3–7 on site). Brick/blockwork, steel install, roof structure, weather-tight.
- Phase 5 — First and second fix (weeks 6–12 on site). Plumbing, electrics, plastering, doors, windows, decorating.
- Phase 6 — Snag & handover (final week). Final BC sign-off, snag list walked with you, photos, warranties.
Recent extensions across Wiltshire & Somerset.
Two storey · Bath
Lansdown · 48m² side
Two-storey side extension on a 1930s semi — extra bedroom & en-suite above an enlarged kitchen. Bath stone match.
Wraparound · Bradford-on-Avon
Bridge Street · 64m² wrap
L-shape wraparound on a Victorian terrace inside the conservation area. Listed Building Consent, lime mortar.
Frequently asked questions.
Do I need planning permission for an extension in Wiltshire or Somerset? +
Many single-storey rear extensions fall under permitted development if they meet size limits — up to 4m for detached houses, 3m for terraced/semi, plus the "larger home extension" neighbour-consultation route up to 8m/6m. Two-storey extensions almost always require planning permission.
Listed properties and conservation areas (parts of Bath, Bradford-on-Avon and Trowbridge town centre) need full planning regardless of size. We handle planning applications with Wiltshire Council and B&NES as part of the project.
How long does a typical house extension take to build? +
A single-storey rear extension typically takes 10–14 weeks on site, from foundations to handover. A two-storey or wraparound extension is usually 16–22 weeks. Add 8–12 weeks beforehand for drawings, planning approval (where needed) and structural calcs.
How much does a house extension cost in 2026? +
As a guide, single-storey rear extensions in Wiltshire are typically £2,200–£2,800 per square metre for a standard build, more for high-specification finishes, large openings or complex roofs. Double-storey adds roughly 50% to a single-storey footprint cost.
We provide a fixed-price written quote after a free site visit so you know the exact number — no per-square-metre guessing.
Will I need a party wall agreement? +
If your extension is built up to or near a shared boundary, or you're excavating within 3m of a neighbour's foundations, the Party Wall Act 1996 applies. We flag this at the quote stage and either work with a party wall surveyor on your behalf or guide you through the notice process.
Can I live in the house during the extension build? +
For most rear and side extensions, yes — we work in stages so you keep the use of the existing kitchen and main rooms until late in the project. The dustiest week is typically the breakthrough into the existing structure; we'll warn you in advance and protect adjoining rooms with dust sheets and zip walls.