Design and build two-storey extensions in Hampshire

Hampshire at a glance

Nation: England
Price region: South East England
Postcode areas: BH, GU, PO, RG, SO, SP
Towns covered: 34 listed below, plus surrounding villages
Site visits: Free, no obligation

What a design and build project involves

This service suits you if you want one team accountable from the first visit to the completion certificate. We manage the design, approvals and build, and the work is carried out by vetted teams working under S&K. Because the same team designs and builds, costs are checked as the design develops. Every project starts with a free site visit.

Towns in Hampshire include Southampton (SO14), Portsmouth (PO1), Basingstoke (RG21), Gosport (PO12), Waterlooville (PO7) and Farnborough (Hampshire) (GU14). If yours isn't listed, we still cover it.

Fees

The design stage is priced in writing before it starts, and the build is a fixed price in writing once the design is agreed.

Rules in England

In England, design and build covers the permitted development check or planning application (£548 (or £575 for applications made from 8 December 2026)), building regulations approval from council building control or a registered approver, Party Wall Act notices where needed, and the Building Safety Act dutyholder roles. We programme them so they overlap where possible.

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

Responsibility for the rules

In England, where more than one contractor is involved, a principal designer and principal contractor must be appointed. On design and build projects we take on these duties, so you are not left holding responsibilities you may not know you had.

Cost checking as you design

Because the people drawing the extension also build it, each design option comes with a guide cost. That avoids the common problem of an approved design that turns out to be too expensive once builders price it.

How we work in Hampshire

Free site visit
We visit your home in Hampshire, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Hampshire.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Towns we cover in Hampshire

Design and build two-storey extensions in Hampshire: questions

Who builds my extension?

Your extension is built by vetted teams working under S&K, with the project managed by us from design to completion. You have one point of contact throughout, and the same team that prepared the design is responsible for the build.

What is the difference between design and build and using an architect?

With an architect, you appoint them for the design and approvals, then find and manage a builder separately. With design and build, one team does both, so cost, buildability and approvals are considered together and there is one point of contact. Some people still prefer to hire an architect separately.

When is the build price fixed?

Once the design is agreed and the drawings, structural calculations and specification are complete. Before that we give guide costs at each stage. The fixed price is set out in writing before work starts, and any changes you ask for after that are priced separately before they are made.

Neighbouring areas

All extension services in Hampshire · About design and build two-storey extensions