Two-storey extensions for end-of-terrace houses 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
Approval route: Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
Site visits: Free, no obligation

What a two-storey extension for an end-of-terrace house involves

This service suits you if you own an end-of-terrace house with land to the side or a reasonable rear garden.

Hertfordshire towns we list: Watford (WD1), Hemel Hempstead (HP1), Stevenage (SG1), St Albans (AL1), Welwyn Garden City (AL6) and Cheshunt (EN7). Every other address in Hertfordshire is covered as well.

Guide price in the East of England

Using our East of England rates, a two-storey extension for an end-of-terrace house with a 3 m × 7 m footprint on two floors (42 m² of new floor space) comes to about £88,500–£119,000, including VAT. Bigger or more glazed designs cost more per m². Design fees, structural calculations and approval fees are separate and listed on our prices page.

Spec	Per m²	Typical project
Essential	£1,940–£2,610 per m²	£81,500–£109,500
Standard	£2,110–£2,830 per m²	£88,500–£119,000
Premium	£2,530–£3,400 per m²	£106,500–£143,000

Rules in England

In England, a two-storey side extension on an end-of-terrace house always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026). A two-storey rear extension can be permitted development within 3 m of the original rear wall and 7 m from the rear boundary. On a corner plot, nothing can go beyond a side wall that fronts a highway under permitted development.

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

Continuing the terrace roof

A side extension on an end-of-terrace house usually continues the roofline of the row, so the pitch, eaves height and tiles must match. A small step down in the ridge and a set-back at the front often help the extension read as an addition rather than an extra house.

Older walls and foundations

Many terraces are older, with shallow footings and solid walls. Tying a new two-storey extension into them needs a careful structural design and sometimes movement joints, and we check the gable wall and its foundations before the design is fixed.

How we work in Hertfordshire

Understand the brief
At your home in Hertfordshire we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Drawings, then consent
We draw the scheme, check it against the rules in England, and take it through the right consent with the council.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.

Towns we cover in Hertfordshire

Two-storey extensions for end-of-terrace houses in Hertfordshire: questions

How much does a two-storey extension for an end-of-terrace house cost in Hertfordshire?

In the East of England our guide is £2,110–£2,830 per m² including VAT, so about £88,500–£119,000 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). Essential and Premium specs move that by roughly 8% down or 20% up.

Can an end-of-terrace house have a wraparound extension?

Yes, if there is room to the side and rear. It combines a side extension over the open plot with a rear extension, and it always needs planning permission in England. It gives a large open-plan ground floor, but it also affects the attached neighbour and the street, so we test it carefully.

Will my end-of-terrace extension look like a new house on the end?

It should not, if it is designed well. A slightly lower ridge, a set-back from the front wall and a different front door position help it read as an extension. Councils often ask for this to avoid an extension that looks like an extra terraced house.

Are old terrace foundations strong enough to extend next to?

Usually, but they need checking. Older terraces often have shallow brick footings, and a new two-storey extension sits on deeper, modern foundations alongside them. The structural engineer designs the junction so the two can move slightly without cracking, and we dig trial holes to see what is there before the design is fixed.

Will I need planning permission in Hertfordshire?

Hertfordshire is in England. Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.

Neighbouring areas

All extension services in Hertfordshire · About two-storey extensions for end-of-terrace houses