Part single, part two-storey extensions in Holywood

Holywood: the key facts for this kind of project.

Postcode districts: BT18
County / area: County Down, Northern Ireland
Price region: Northern Ireland
Guide price: £63,500–£87,000 (£1,760–£2,420 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: Dundonald (3.4 miles), Newtownabbey (3.7 miles), Jordanstown (4.3 miles)
Distance to Bangor (County Down): about 6.4 miles
First visit: Free, no obligation

About a part single, part two-storey extension

A part single, part two-storey extension is an extension where the ground floor is wider or deeper than the floor above, so only part of it rises to two storeys. It usually gives a large kitchen or living area with roof lights below and one bedroom or bathroom above. It is often a good way to add space while limiting the effect on neighbours.

Holywood sits about 6.4 miles from Bangor (County Down). Closer to home, Dundonald is 3.4 miles away and Newtownabbey 3.7 miles.

What it costs in Holywood

In Northern Ireland, which includes Holywood, we'd expect a part single, part two-storey extension to cost around £63,500–£87,000 for a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total), or £1,760–£2,420 per m² including VAT. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

Spec	Per m²	A 6 m × 4 m ground floor and a first floor over half of it (36 m² in total)
Essential	£1,620–£2,230 per m²	£58,500–£80,000
Standard	£1,760–£2,420 per m²	£63,500–£87,000
Premium	£2,110–£2,900 per m²	£76,000–£104,500

Planning and building control in Holywood

In Northern Ireland, the 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 height, materials and roof pitch conditions met. Specified protected areas are excluded. If the design goes further, a planning application costs £347 per dwelling, and building control approval is needed either way.

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 Holywood homes

Where to put the two-storey part

The two-storey section usually works best away from the closest neighbour, with the single-storey part on that boundary side. We test a few positions against neighbours' windows, the upstairs layout and the roof shape before choosing the one to take forward.

Structure at the step

The first-floor wall above often sits over the new open-plan space, so it needs a steel beam or frame to carry it. Loads come down at different points than in a full two-storey design, and the engineer sizes the foundations to suit each part.

How we'd run your project

Free site visit
We visit your home in Holywood, look at the structure, access and boundaries, and talk through what you want the new rooms to do.
Drawings, then consent
We draw the scheme, check it against the rules in Northern Ireland, and take it through the right consent with the council.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Questions about part single, part two-storey extensions in Holywood

Which postcodes do you cover around Holywood?

We cover Holywood (BT18) and nearby places including Dundonald, Newtownabbey and Jordanstown, plus the rest of County Down. The first site visit is free.

How much does a part single, part two-storey extension cost in Holywood?

Our guide for Northern Ireland, which covers Holywood, is £1,760–£2,420 per m² including VAT. A typical project with a 6 m × 4 m ground floor and a first floor over half of it (36 m² in total) comes to about £63,500–£87,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Do I need planning permission for a part single, part two-storey extension in Holywood?

Holywood 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.

Can the single-storey part be deeper than the two-storey part?

With planning permission, yes, and that is often the point of the design: the ground floor projects further into the garden while the first floor stays back from neighbours. Under permitted development, the depth limits for extensions of more than one storey can apply to the whole extension, so we confirm which route applies before drawings are finalised.

Which side should the two-storey part go on?

Usually the side furthest from the nearest neighbour's windows, so the single-storey part sits nearest them and keeps their light. Other factors are where the stairs land upstairs, which room needs the extra space and where drains run. We sketch options at the design stage and explain which is most likely to be approved.

Nearby

Other towns near Holywood:

Other extensions in Holywood

All two-storey extension services in Holywood · Part single, part two-storey extensions across County Down

The quickest next step is a visit. We'll look at your house in Holywood and give you an honest view of the options.