What is a structural alteration?
A structural alteration changes how a house carries its loads, most often by removing a load-bearing wall and replacing it with a steel beam. It is how kitchens and dining rooms become open-plan, and how extensions are joined to the original house.
How much does a structural alteration cost in Cardiff?
In Cardiff, a structural alteration typically costs £4,250–£8,750 for a typical knock-through with steel beam, including VAT at 20% (standard rate). Prices across Wales are typically 8% below the UK average for this kind of work, which is reflected in the range for Cardiff. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| A typical knock-through with steel beam | £4,250–£8,750 |
| Higher specification | £8,750–£11,000 |
Your quote will depend mainly on:
- Moving radiators, sockets and pipes
- Floor and ceiling repairs
- Party wall involvement
- Span of the opening
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a structural alteration in Cardiff?
Here is how the rules work for a structural alteration in Wales. In Wales removing a load-bearing wall needs building regulations approval with structural calculations, and party wall notices where a shared wall is involved.
The Party Wall etc. Act 1996 applies in Wales, so notices must be served before work on a shared wall, on the boundary, or excavation close to a neighbour’s foundations.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
What we take care of:
- Party wall notices where needed
- Making good, plastering and flooring repairs
- Building control sign-off
- Fire protection to the steel
- Building control application
- Structural engineer’s calculations and drawings
How long does it take?
Expect 1 to 2 weeks on site for a typical knock-through. Before that, surveys, drawings and approvals usually take 6 to 12 weeks, longer if the council asks for changes.
Building in Cardiff
Wales has many terraced valley streets, stone cottages and post-war estates, so extension designs are shaped by slopes, materials and local character.
Our Cardiff coverage includes postcode districts CF10, CF11, CF14 and CF15, and we also work in nearby places such as Penarth, Caerphilly and Barry.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about structural alterations in Cardiff
Can the beam be hidden?
Often, by setting it within the ceiling depth. It depends on the joists and span.
Do I need planning permission for a structural alteration in Cardiff?
In Wales removing a load-bearing wall needs building regulations approval with structural calculations, and party wall notices where a shared wall is involved.
Do I need building regulations approval?
Yes. Removing a load-bearing wall is building work that needs approval, with calculations for the beam.
Who approves a structural alteration in Cardiff?
Planning matters in Cardiff go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
What fire protection does a steel need?
Usually fire-rated plasterboard or intumescent paint, as building control requires.
How much does a structural alteration cost in Cardiff?
In Cardiff, a structural alteration typically costs £4,250–£8,750 for a typical knock-through with steel beam, including VAT at 20% (standard rate). Your fixed price depends on the survey and drawings.