Skip to Content

House Extensions in Cardiff


At Mark James Building Contractors, we build high-quality house extensions in Cardiff and surrounding areas. Whether you’re looking to add extra living space, create an open-plan kitchen-diner, or improve the layout of your home, we deliver extensions built to a high standard with excellent finishes.

Free quotes available

Clear communication & reliable timelines

High-quality workmanship from start to finish

Types of Extensions We Build

We can help with a wide range of extension projects, including:

Single story rear extension cardiff

Single Storey Extensions

A popular option for adding extra living space, extending kitchens, or creating open-plan layouts..

Rear story extension cardiff

Rear Extensions

Ideal for larger kitchen-diners, family living spaces and modern open-plan upgrades.

Double extension cardiff

Side Extensions

Great for widening narrow properties, adding utility space, or extending ground floor rooms.

Kitchen cardiff

Wraparound Extensions

A bigger transformation that maximises space and completely changes how your home works..

What’s Included in Our Extension Work

What’s Included in Our Extension Work

Structural works & knock-throughs Steel installation (RSJs) where required 
Brickwork, blockwork and external finishes 
Roofing and insulation 
Internal plastering and finishing 
Coordination of plumbing & electrics 
doors, windows and final fit-out

Why Extend Your Home?

A well-planned extension can:

  • Add significant value to your property

  • Create the space you need without moving

  • Improve layout and natural light


    Modernise and upgrade your home

Why Choose Mark James Building Contractors

We’re proud to be known as reliable Cardiff builders who deliver quality results and a clean finish.

  • High standards of workmanship

     
    Professional, friendly team

     
    Reliable communication throughout

     
    Strong attention to detail

see some examples of our extensions

 Check our our recent projects   


Frequently asked questions

Here are some common questions about our company.

Costs depend on size, access, finishes and the type of extension. Contact us and we’ll provide a clear quote based on your plans.

Yes — we can manage the build from start to finish and keep everything organised and on schedule.


Timeframes vary depending on the size and complexity, but we’ll always give you realistic timelines before starting.

As 436 clients before you, let’s work together


Get a Free Quote for Extension

if you’re planning an extension in Cardiff or nearby, get in touch today.

Contact us for a free quote and advice.

Contact us