Building Awards 2026 shortlists: Specialist or Main Contractor of the Year (under £500m), sponsored by Clement Windows Group

Earlier this year Building announced the names of all the firms that made it onto the shortlists for our prestigious annual Building Awards.

Now we are shining the spotlight on each category in turn and publishing a selection of the images that impressed the judges.

Today’s shortlist is for the Specialist or Main Contractor of the Year (under £500m), sponsored by Clement Windows Group.

Britcon

Britcon has combined financial resilience, operational performance and cultural growth through a people-first approach, integrated delivery and investment in innovation. The family-owned contractor grew its workforce by 13% to 102, while all projects were delivered to programme and three ahead of schedule. Digital investment of more than £700,000 contributed to a 14% productivity increase and streamlined manual tasks by up to 80%. Customer performance remains strong, with a 100% client referral rate, 82% repeat business and an average feedback score of 8.9/10. Sustainability progress includes a 26% carbon reduction, fifth-year Planet Mark certification and more than £32m in social value. Employee net promoter score reached 92, attrition fell to 7%, and apprenticeships doubled, while safety performance also improved.

ESG

Celebrating 50 years in the UK construction industry, ESG combines technical excellence with digital innovation, offsite manufacturing and a strong people-first culture. Its Technology in Construction initiative uses advanced BIM co-ordination, hyperreal visualisation and the proprietary MySiteDocs platform to improve design accuracy, safety, compliance and project delivery. Dedicated prefabrication facilities embed DfMA principles, accelerating programmes, improving quality and reducing environmental impact, particularly on technically demanding projects.

Since becoming an employee ownership trust, ESG has built a culture of accountability, collaboration and shared success, reflected in strong employee engagement and workforce stability. Its craft and technical academy and its membership of The 5% Club support future skills, with women now representing 36% of apprentices. Recognition from the Electrical Contractors’ Association (ECA) and the Building Engineering Services Association (BESA) for ESG’s work in sustainability and inclusion reinforces its progressive approach to engineering.

GMI Construction Group

GMI has strengthened its position as a resilient, progressive contractor, with turnover of £233m and forecast growth to £280m. Its strategic response to market pressures has prioritised selectivity, early engagement and stronger client relationships, supported by improved CRM intelligence and regional planning. This approach has delivered projects including Valerian, York, and Dakota Manchester Airport four weeks ahead of programme, while expanding public sector capability through four NEPO framework projects.

GMI’s delivery model is underpinned by values focused on collaboration, empowerment and innovation, alongside investment supporting more than 120 apprentices, graduates and early-career participants. Sustainability is embedded through low carbon materials, efficient logistics and energy performance. Health, safety and social value remain central, with education partnerships creating meaningful pathways into construction and local communities.

Kilnbridge

Kilnbridge has delivered one of the strongest years in its 35-year history, combining specialist expertise, technical excellence and disciplined delivery across complex infrastructure and building projects. Its material-agnostic approach integrates concrete structures, fire protection, steel fabrication, temporary works and specialist engineering, reducing interfaces and improving risk control. Major projects including HS2 Old Oak Common, the Colne Valley Viaduct, Clifton Bridge and One North Quay demonstrate its ability to deliver technically demanding packages safely and to programme.

Safety performance was particularly strong, with 16,360 proactive reports and a 230% increase in near-miss reporting, reflecting a mature safety culture. As an employee-owned business, Kilnbridge also invested in its people while contributing to the Accelerating Concrete Decarbonisation Group, helping develop practical low-carbon concrete solutions.

RED Group

RED Group has strengthened its position as a progressive UK contractor through strategic growth, integrated delivery and investment in people. Turnover rose almost 50% to £171m in FY24/25, with further growth forecast, supported by expanded regional and specialist capabilities. Its integrated model has improved co-ordination and certainty on complex schemes, including the £52m 40 Broadway, delivered on time and budget.

Sustainability is embedded through the RED to Green strategy, with projects including Bruton Place in London’s Mayfair achieving 424.1kgCO₂e/m² and The Harrison in Shoreditch 341kgCO₂e/m². RED also delivered Europe’s first net zero carbon branded hotel, voco Zeal Exeter. Alongside this, employee engagement reached 99%, more than 1,000 hours of CPD were delivered, and social value exceeded £200,000 in charitable fundraising.

SES

SES is redefining specialist contracting through engineering excellence, digital innovation, offsite manufacturing and sustainable delivery. Its Digital First approach combines advanced modelling and collaboration tools with precision-engineered offsite solutions, improving quality, safety, programme certainty and building performance. In 2025, almost 33,000 manufactured components removed 309,801 hours of work from sites, reducing waste and improving productivity.

Sustainability is embedded throughout the business. SES has cut operational carbon emissions by 47% since 2019, sources 93% of its energy from renewables and is committed to achieving net zero carbon by 2045. Meanwhile, investment in people has supported 102 apprentices and trainees, alongside £54,728 of community investment, 771 volunteering hours and engagement with more than 7,200 students.