Donald Insall Associates, also known as DIA, is an employee-owned architectural practice and heritage consultancy founded in 1958. Its work combines the care of historic buildings with their adaptation for continued use, alongside new architecture in sensitive settings and advice on the development of towns and cities.
The practice works with private owners, country estates, public institutions, local authorities, developers and preservation trusts. Its role is architectural and advisory: investigating significance, developing proposals and guiding projects, rather than supplying building trades as a conservation contractor.
Services include feasibility and options studies, condition surveys, quinquennial inspections, historic interiors, repair design and funding advice. The practice works with churches, cathedrals, memorials and historic landscapes as well as individual buildings.
Its approach begins with understanding a place's history, materials and construction. The aim is to identify how change can support continued use while respecting the qualities that make a building significant.
Heritage services include impact assessments, conservation management planning, designation advice, building recording and expert-witness work. Published capabilities also include digital heritage, geographic information systems and three-dimensional surveys. Consultancy can support an external design team or be combined with DIA's architectural services.
DIA designs adaptations, extensions and new buildings in historic settings. Its published approach considers the character, materials and use of the existing place when developing new interventions.
Sustainability is addressed through the continued use of existing buildings, decisions about materials and consideration of whole-life carbon. The practice advocates durable, adaptable designs rather than assessing environmental performance solely through energy use in occupation.
The practice provides townscape and visual impact assessments, advice for masterplans and specialist advocacy. This work considers how the scale, views and setting of a proposal relate to the surrounding historic environment.
Between 2010 and 2020, Donald Insall Associates worked with Alan Baxter and the UK Parliament on a phased conservation programme at Westminster Hall. The work addressed masonry, windows, the medieval hammerbeam roof and the roof lantern. The project received a 2024 European Heritage Award / Europa Nostra Award, recognising a programme that combined detailed investigation, fabric conservation and carefully integrated improvements.
DIA designed the conservation and reuse of the Grade II*-listed Camellia House as a public tearoom and events venue. The project retained the historic camellias in place during construction and combined traditional repairs with improvements including a ground-source heat pump and rainwater harvesting. It received a 2025 European Heritage Award / Europa Nostra Award.
The practice was the architect for the John Rylands Library's Next Chapter project, working with the University of Manchester and exhibition designers Nissen Richards Studio. Completed in 2025, the project renewed exhibition and visitor spaces, introduced a specialist imaging laboratory and created flexible accommodation for events and teaching within the Grade I-listed library. The work illustrates the adaptation of a historic institution to support research and public access.
Donald Insall Associates appears in RIBA's practice directory and the Institute of Historic Building Conservation's Historic Environment Service Providers Recognition (HESPR) scheme. Its team includes architects individually registered with Architects Accredited in Building Conservation (AABC).
The practice has been a Certified B Corporation since July 2024. B Corp certification concerns the business's social and environmental performance; it is distinct from professional architectural registration and individual conservation accreditation.
Initial enquiries can identify the property or site, its location, any heritage designation and the proposed scope of work. Existing drawings, surveys and photographs can help explain whether the requirement is for architectural design, specialist heritage advice, a condition assessment or townscape analysis.
The practice has a UK-wide remit supported by regional teams. Confirm the appropriate studio, proposed professional team and scope of appointment directly.
London office:
12 Devonshire Street
London W1G 7AB
Telephone: 020 7245 9888
Email: info@dia.co.uk
Website: dia.co.uk
| Services & Expertise | |
|---|---|
| Principal Areas of Work: | Conservation architecture, Heritage consultancy, Historic building repair and adaptation, New design in heritage settings, Townscape advice |
| Capabilities and Specialisms: | Conservation Architecture, Heritage Consultancy, New Design in Heritage Settings, Townscape Advice, Sustainability, Historic Building Adaptation, Cultural Significance Assessment, Restoration Projects |
| Accreditations, Certifications & Memberships : | RIBA practice directory listing, IHBC HESPR recognition, AABC-registered architects within the practice, Certified B Corporation |
| Accreditation & Membership Details: | The practice appears in RIBA's Find an Architect directory and the IHBC HESPR register. The AABC register lists individual architects associated with Donald Insall Associates; this is individual accreditation, not a company-wide AABC certification. B Lab records B Corp certification from July 2024. |
| Geographical Areas Covered: | United Kingdom; international commissions by enquiry. |
| Contact & Online Presence | |
| Email: | info@dia.co.uk |
| Business Details & Assurance | |
| Company Trading Name: | DONALD INSALL ASSOCIATES LIMITED |
| Company Number: | 1550406 |
| Public Liability Insurance: | Yes |
| Professional Indemnity Insurance: | Yes |
