Design and build two-storey extensions in Kent

Kent at a glance

Nation: England
Price region: South East England
Postcode areas: BR, CT, DA, ME, TN
Towns covered: 31 listed below, plus surrounding villages
Site visits: Free, no obligation

What a design and build project involves

A design and build project for a two-storey extension involves one team taking responsibility for the whole job: the survey, design, planning or permitted development, structural engineering, building regulations, party wall matters where they apply and the construction itself. You deal with one point of contact instead of coordinating an architect, engineer and builder separately. The design stage is priced first, then the build at a fixed price.

Across Kent we cover Maidstone (ME14), Gillingham (ME3), Chatham (ME4), Tunbridge Wells (TN1), Folkestone (CT18) and Margate (CT9), plus the smaller places around them.

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

How the stages work

We start with a free site visit, then a design stage priced in writing before it begins. That covers the survey, design, approvals, structural design and building regulations. Once the design is agreed, the build price is fixed in writing before work starts.

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 Kent

Free site visit
We visit your home in Kent, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Towns we cover in Kent

Design and build two-storey extensions in Kent: questions

Do I have to use you for the build if I pay for the design stage?

No. The design stage is priced separately, so you can take the approved drawings to other builders if you choose. Most people who use design and build carry on to the build, because the design has been costed as it developed.

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.

Neighbouring areas

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