Welcome to the website of A.T. Design (Welwyn) Ltd.

We are an Architectural design practice specialising in medium to large residential extensions in Hertfordshire and the surrounding areas.

For new enquires please use the email address below with your address and a brief outline of your ideas.


Specialising in medium to large sized extensions and new build houses in Hertfordshire.

Replacement dwelling in Bassingbourne

References and examples of work provided on request

New Gym and swimming pool

New dwelling in Harpenden

Due to current workload, lead in times are currently 5-6 weeks for new work. 


Latest news:

Two new dwellings are close to completion in Littlington, near Royston. Photographs to follow.

Side extension in WGC

Commercial property in WGC