Gas & Oil Boilers Specialists

Our qualified engineers offer a full range of services, including installation, replacements, servicing or repair of your gas and oil boilers. With years of experience behind us, we guarantee our customers the highest quality.

Aga & Rayburn Experts

We are proud members of the Rayburn Guild and all of our engineers are experienced in the installation, service and repair of the entire range of Rayburn and Aga cast iron ranges and stoves.

Wood Burner Installation

Our engineers are experienced in the installation, service, maintenance and repair of all different kinds of wood burners. We can also offer you expert advice on your project.

Serving Our Customers

Abergavenny, Brecon, Usk and South Wales

Gas Mark One was founded in 2000 by experienced former British Gas engineer Mark Barrier. His mission was to help local residents and businesses cut their costs on their plumbing and heating.

We offer a quality, efficient and reliable service from our base in Abergavenny. Our engineers cover the surrounding area, travelling throughout Monmouthshire and south Wales, as far afield as Brecon.

Mark, who has over 25 years of experience in the industry, once appeared on the BBC’s DIY SOS programme. Our engineers have installed hundreds of Worcester Bosch boilers, Aga wood burners and Rayburn range cookers and continue to serve the local community.

Gas Mark One is proud to be endorsed as a Which Trusted Trader, check out our reviews by clicking on the icon below.

Contact us for more information

Emergency Call Outs

We operate a 24-hour emergency call-out service in Abergavenny and the surrounding area. Our qualified engineers can help you with all of your plumbing, drainage, boiler, gas central heating, Aga and Rayburn emergencies.


We help landlords to survey carbon monoxide risks in their property. All of our Gas Safe Registered engineers are also qualified to carry out inspections and issue the certificates required by the Health and Safety Executive.


Whatever your drainage issue, Gas Mark One have all of the tools to help resolve it. Whether it is a persistent problem or simply a one-off, our experts will fix the job properly and not just implement a quick fix.


We have over 25 years of experience in the industry. Click below to see what some of our customers have said about us.