Structural engineering for two-storey extensions in Dyfed

Dyfed at a glance

Nation: Wales
Price region: Wales
Postcode areas: SA, SY
Towns covered: 21 listed below, plus surrounding villages
Site visits: Free, no obligation

What a structural design involves

Structural engineering for a two-storey extension involves calculating how the new floors, walls and roof carry their loads down to the ground, and designing the beams, lintels, foundations and ties into the existing house to suit. The engineer's calculations and drawings form part of the building regulations approval. They also tell the build team exactly what steel and foundations to install.

Dyfed towns we list: Llanelli (SA15), Ammanford (SA18), Aberystwyth (SY24), Carmarthen (SA31), Haverfordwest (SA61) and Milford Haven (SA73). Every other address in Dyfed is covered as well.

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 Wales

In Wales, structural design is checked under the Welsh building regulations, Part A, as part of a full plans application to building control. The engineer's calculations and drawings are submitted with the architectural drawings, and the building control surveyor inspects foundations and key structural stages on site.

Approval in Wales: Householder planning application: £585. Councils normally decide householder applications within 8 weeks.

Building regulations: Building regulations approval under the Welsh Approved Documents, which differ from England's in places (notably energy efficiency).

The Party Wall etc. Act 1996 applies in Wales, so notices may be needed for work on or near a shared wall or boundary.

Getting the design right

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.

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.

How we work in Dyfed

Look at the house
We start in Dyfed with a free visit: measurements, photos, a look at the loft and drains, and a frank chat about budget.
Drawings, then consent
We draw the scheme, check it against the rules in Wales, 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 it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.

Towns we cover in Dyfed

Structural engineering for two-storey extensions in Dyfed: questions

What are trial holes and why do I need them?

Trial holes are small excavations dug next to the house or garage to see the depth and condition of the existing foundations and the soil. They tell the engineer whether existing footings can be reused and how deep the new ones need to go, which avoids surprises during the build.

Will the engineer visit the site during the build?

Not usually at every stage. Building control inspects the foundations, steelwork and other key stages against the approved calculations. The engineer is called back if site conditions differ from the design, such as unexpected ground, hidden beams or weak existing walls, and issues revised details before that part of the work continues.

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.

Neighbouring areas

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