Structural engineering for two-storey extensions in County Londonderry

County Londonderry at a glance

Nation: Northern Ireland
Price region: Northern Ireland
Postcode areas: BT
Towns covered: 11 listed below, plus surrounding villages
Site visits: Free, no obligation

What a structural design involves

This service suits every two-storey extension, because each one needs foundations sized for two storeys and usually steel beams where walls are removed. You get a structural engineer's calculations and drawings for beams, padstones, lintels, foundations and connections, coordinated with the architectural drawings, submitted for building control and followed through on site by our build teams.

Towns in County Londonderry include Derry (BT48), Coleraine (BT51), Limavady (BT49), Magherafelt (BT45), Portstewart (BT55) and Portrush (BT56). If yours isn't listed, we still cover it.

Fees

A structural engineer (calculations and beam design) is a guide of £750–£2,200, priced in writing once the design is known.

Rules in Northern Ireland

In Northern Ireland, structural design is checked by the council's building control service under the Building Regulations (Northern Ireland) and the relevant Technical Booklet. The engineer's calculations are submitted with the full plans, and building control inspects foundations, steelwork and other key stages during the build.

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

Building on existing structure

When building over a garage or a single-storey extension, the engineer checks the existing footings, walls and lintels. Many were sized for one storey only and need underpinning, strengthening or replacement to carry the new floor.

Tying into the house

The new walls and floors are tied into the existing house with wall ties, restraint straps and joist hangers. The engineer also considers movement between the old and new foundations and where a movement joint may be needed.

How we work in County Londonderry

Understand the brief
At your home in County Londonderry we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Design and approvals
We draw the extension and check it against the rules for Northern Ireland, then apply for planning permission or a certificate of lawfulness, whichever fits.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Towns we cover in County Londonderry

Structural engineering for two-storey extensions in County Londonderry: questions

Do I need a structural engineer for a two-storey extension?

Almost always. Building control needs calculations showing that the foundations, beams and walls can carry the loads of two storeys and a roof. A two-storey extension usually involves removing part of an outside wall and new steel, which needs an engineer's design.

Can a steel beam be hidden in the ceiling?

Often, yes. A beam can sit within the floor depth so the ceiling is flat, but that may mean a deeper steel section or a different floor structure. Otherwise it shows as a downstand below the ceiling. We discuss the options with you and the engineer before the design is fixed.

How deep do foundations need to be for a two-storey extension?

There is no single depth. It depends on the soil, nearby trees, drains and the loads. On firm ground foundations may be around a metre deep, while clay near trees can need much deeper trench fill or piles. Trial holes and the engineer's design set the depth, and building control inspects the trenches.

Neighbouring areas

All extension services in County Londonderry · About structural engineering for two-storey extensions