Two-storey rear extensions in Greenisland

The basics for Greenisland at a glance.

Postcode districts: BT37
County / area: County Antrim, Northern Ireland
Price region: Northern Ireland
Guide price: £49,500–£66,500 (£1,760–£2,380 per m²)
Approval route: It may be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary.
Nearest towns: Jordanstown (1.6 miles), Carrickfergus (2.9 miles), Newtownabbey (3.1 miles)
Distance to Belfast: about 7.5 miles
First visit: Free, no obligation

About a two-storey rear extension

A two-storey rear extension suits you if you need more room on both floors and have a reasonably deep garden. You get one team for the whole job: a measured survey, the design, a check on whether permitted development applies, planning drawings where they are needed, structural design, building regulations approval and the build itself, carried out by vetted teams working under S&K. Every project starts with a free site visit.

Around Greenisland we also work in Jordanstown, Carrickfergus and Newtownabbey, and across the rest of County Antrim. Postcode district in and near Greenisland: BT37.

What it costs in Greenisland

In Northern Ireland, which includes Greenisland, we'd expect a two-storey rear extension to cost around £49,500–£66,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), or £1,760–£2,380 per m² including VAT. Keep a contingency of around 10% for things nobody can see until the ground is opened up.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£1,620–£2,190 per m²	£45,500–£61,000
Standard	£1,760–£2,380 per m²	£49,500–£66,500
Premium	£2,110–£2,850 per m²	£59,000–£80,000

Planning and building control in Greenisland

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 at least 7 m from the rear boundary, with conditions on height, materials and roof pitch. Upper side windows within 15 m of a neighbouring boundary must be obscure-glazed and non-opening. Otherwise a planning application costs £347 per dwelling.

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.

Design points for Greenisland homes

Depth and neighbours' light

Councils check that a two-storey rear extension does not take too much light or outlook from neighbouring windows, and many use a 45-degree line drawn from the nearest habitable window. We test this at sketch stage, so the depth you are shown is one that can realistically be approved.

Opening up the ground floor

Knocking through the old rear wall means steel beams to carry the first floor and roof above. The structural engineer sets the beam sizes, padstones and any posts, and we plan them early so the open-plan layout you want is the one that gets built.

How we'd run your project

Visit and first ideas
One of our team visits your house in Greenisland, checks the walls, roof and drains, and sketches out options with you.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in Northern Ireland before drawing in detail.
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.
Build it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.

Questions about two-storey rear extensions in Greenisland

Who handles building control for a project in Greenisland?

We handle it as part of the project. What's needed in Northern Ireland: building control approval from the local council under the Building Regulations (Northern Ireland), using the Technical Booklets. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.

Do I need planning permission for a two-storey rear extension in Greenisland?

Greenisland is in Northern Ireland. It may be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary.

Which postcodes do you cover around Greenisland?

We cover Greenisland (BT37) and nearby places including Jordanstown, Carrickfergus and Newtownabbey, plus the rest of County Antrim. The first site visit is free.

How long does a two-storey rear extension take?

Allow 4 to 8 weeks for survey and design, then the approval period (councils aim to decide local applications within an average of 15 weeks; many take longer), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.

Will a two-storey rear extension block my neighbour's light?

It can if it is too deep or too close to the boundary, which is why councils look closely at its effect on neighbouring windows and gardens. We test the design against light and outlook early, keep the first floor shorter or set in where needed, and use a hipped roof to reduce bulk on the boundary side.

Nearby

Other towns near Greenisland:

Other extensions in Greenisland

All two-storey extension services in Greenisland · Two-storey rear extensions across County Antrim

Want a figure first? Try our guide price tool, then book a free visit to firm it up.