Planning permission for two-storey extensions in Hertfordshire

Hertfordshire at a glance

Nation: England
Price region: East of England
Postcode areas: AL, CM, EN, HP, SG, WD
Towns covered: 33 listed below, plus surrounding villages
Site visits: Free, no obligation

What a planning application involves

This service suits you if you want your two-storey extension to go through planning with the best chance of approval. You get a check of your house's planning history, permitted development rights and local design guidance, a design shaped around them, the application prepared and submitted, and someone to deal with the planning officer's questions. We cannot promise an outcome, but we design to give the application a fair chance.

Across Hertfordshire we cover Watford (WD1), Hemel Hempstead (HP1), Stevenage (SG1), St Albans (AL1), Welwyn Garden City (AL6) and Cheshunt (EN7), plus the smaller places around them.

Fees

Planning drawings are a guide of £2,000–£3,500, priced in writing before the design stage starts. 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).

Rules in England

In England, a householder planning application costs £548 (or £575 for applications made from 8 December 2026), and councils should decide within 8 weeks of validation. Two-storey side, wraparound and front extensions always need permission. Rear extensions may be permitted development within the 3 m and 7 m limits, confirmed with a lawful development certificate costing £274 (about £288 for applications from 8 December 2026).

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

Design to local guidance

Most councils publish guidance on extensions covering set-backs, roof heights, boundary gaps and neighbours' light. Designing to it from the start makes approval more likely and reduces the chance of being asked to make changes during the application.

Check the history first

Planning conditions from when the house was built, earlier extensions and Article 4 directions can all remove permitted development rights. We check the council's records and your house's history before design starts, so the route is clear.

How we work in Hertfordshire

Measure and listen
A visit to Hertfordshire to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.

Towns we cover in Hertfordshire

Planning permission for two-storey extensions in Hertfordshire: questions

What happens if my planning application is refused?

You can change the design and apply again, or appeal. In England, a householder appeal must usually be made within 12 weeks of the decision. Often the best route is a revised design that answers the reasons for refusal. We read the officer's report and advise which option has the better chance.

Should I get pre-application advice from the council?

It can help on sensitive sites, such as conservation areas, corner plots or front extensions, where the council's view is hard to predict. Many councils charge for it and response times vary. For straightforward designs that follow local guidance, a well prepared application is often the quicker route.

Neighbouring areas

All extension services in Hertfordshire · About planning permission for two-storey extensions