Two-storey extensions for end-of-terrace houses in County Antrim

County Antrim at a glance

Nation: Northern Ireland
Price region: Northern Ireland
Postcode areas: BT
Towns covered: 15 listed below, plus surrounding villages
Approval route: Planning permission is needed: permitted development side extensions in Northern Ireland can't be more than 4 m high, which rules out two storeys.
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.

The main places we list in County Antrim are Belfast (BT1), Lisburn (BT10), Newtownabbey (BT36), Castlereagh (BT4), Carrickfergus (BT38) and Ballymena (BT42). We cover the villages in between too.

Guide price in Northern Ireland

Guide prices for two-storey extensions for end-of-terrace houses in Northern Ireland are around £1,800–£2,420 per m² of new floor space, including VAT. For a typical project with a 3 m × 7 m footprint on two floors (42 m² of new floor space), that's roughly £76,000–£101,500. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

Spec	Per m²	Typical project
Essential	£1,660–£2,230 per m²	£69,500–£93,500
Standard	£1,800–£2,420 per m²	£76,000–£101,500
Premium	£2,160–£2,900 per m²	£91,000–£122,000

Rules in Northern Ireland

In Northern Ireland, a two-storey rear extension can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary, with height, materials and roof pitch conditions. A two-storey side extension normally needs a planning application costing £347 per dwelling. There is no Party Wall Act.

Approval in Northern Ireland: Planning application for works to a house: £347. Councils aim to decide local applications within an average of 15 weeks; many take longer.

Building control: Building control approval from the local council under the Building Regulations (Northern Ireland), using the Technical Booklets.

There is no Party Wall Act in Northern Ireland. Shared walls and boundaries are a matter of title and common law, so we agree access and record conditions with neighbours before work starts.

Getting the design right

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.

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.

How we work in County Antrim

Start at your house
We come to your home in County Antrim, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Get it approved
Once you're happy with the design we submit it to the council for County Antrim and deal with any questions from the planning officer.
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.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Towns we cover in County Antrim

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

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

In Northern Ireland our guide is £1,800–£2,420 per m² including VAT, so about £76,000–£101,500 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.

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.

Can I build a two-storey side extension on a corner plot?

Often, but it needs planning permission and careful design. Councils protect the openness of corners and the view along the road, so they usually expect a gap to the pavement, a set-back from the front and a side wall with windows rather than a blank wall. We check local guidance and nearby examples first.

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.

Will I need planning permission in County Antrim?

County Antrim is in Northern Ireland. Planning permission is needed: permitted development side extensions in Northern Ireland can't be more than 4 m high, which rules out two storeys.

Neighbouring areas

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