Two-storey extension plans and drawings in Wiltshire

Wiltshire at a glance

Nation: England
Price region: South West England
Postcode areas: BA, SN, SP
Towns covered: 14 listed below, plus surrounding villages
Site visits: Free, no obligation

What a set of extension plans involves

This service suits you if you want clear, accurate plans for a two-storey extension, whether to apply for planning, check permitted development or get build prices. You get a measured survey, sketch options with guide costs, a chosen design developed into planning drawings and, if you go ahead, building regulations drawings coordinated with the structural engineer. Because we also build, the drawings are prepared with the build in mind.

Towns in Wiltshire include Swindon (SN1), Salisbury (SP1), Trowbridge (BA14), Chippenham (SN15), Melksham (SN12) and Warminster (BA12). If yours isn't listed, we still cover it.

Fees

Planning drawings (survey and design) are a guide of £2,000–£3,500 and building regulations drawings and specification £1,500–£4,000, with your design stage priced in writing before it starts.

Rules in England

In England, the plans support either a householder application, costing £548 (or £575 for applications made from 8 December 2026), or a lawful development certificate for permitted development, costing £274 (about £288 for applications from 8 December 2026). They must show the extension's relationship to the original house, the boundaries and neighbours, because two-storey rear permitted development depends on the 3 m and 7 m limits.

Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.

Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.

The Party Wall etc. Act 1996 applies, so notices may be needed for work on or near a shared wall or boundary.

Getting the design right

Compare options early

Sketching two or three layouts, such as rear, side or part two-storey, is the cheapest point to make big decisions. Each option comes with a guide cost and a view on the approval route, so you choose with the full picture rather than discovering limits later.

Start with a measured survey

Accurate drawings depend on accurate measurements of the house, the boundaries and neighbouring windows. We measure inside and out, note levels, drains and trees, and record the original house so permitted development limits can be checked against the right starting point.

How we work in Wiltshire

Visit and first ideas
One of our team visits your house in Wiltshire, checks the walls, roof and drains, and sketches out options with you.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Wiltshire.
Price it properly
Once the engineer's calculations are in, we fix the build price in writing, with a clear list of what's included.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.

Towns we cover in Wiltshire

Two-storey extension plans and drawings in Wiltshire: questions

Do the plans include structural calculations?

Not at planning stage. Structural calculations and beam design are prepared by a structural engineer once the design is agreed, and they form part of the building regulations package. We coordinate the engineer's work with the drawings so steel sizes and floor depths match.

Can I use plans from a previous owner's planning permission?

Sometimes. If the permission is still valid, usually within three years of the decision in England, you can build to it. The drawings may still need updating for building regulations, and the design may not suit your needs. We check old plans and permissions at the free site visit.

Do I own the plans once they are drawn?

You receive copies of the drawings to use for your project, including your planning application and building regulations approval. Copyright in drawings normally stays with whoever prepares them unless agreed otherwise. Your written design stage price sets out how the drawings can be used.

Neighbouring areas

All extension services in Wiltshire · About two-storey extension plans and drawings