Bottle Works, Guildford

Client: Soprema

The Bottle Works in Guildford has a long history at the centre of town life. It was first built in the early 1900s for brewing ginger beer and later became one of the largest milk bottling plants in the UK. With great care taken to preserve its historical character, the site has now been restored as a 39,000 sq ft office space that prioritises sustainability and occupant wellbeing. 

Converting a historic bottle works into a sustainable office

As well as restoring the original building once used by R White and Sons and Unigate dairy, Hale Brown Architects were tasked by Kingsbridge Estates with updating the second building on the site, an extension built in the 1990s. Sub-contractors Mariner Projects worked closely with Soprema to design and build a flat roof system for the extension that met fire safety requirements and enhanced the aesthetic character of the original building. Knauf Insulation’s Rocksilk® Flat Roof Slab Extra was chosen by Soprema for the insulation.

Aesthetics, performance and safety 

Hale Brown Architects had a challenging brief for this project. It was important to preserve the history of the site and enhance its facilities, offering an office space that was sustainable and actively promoted the well-being of occupants working there every day. The firm were targeting a BREEAM ‘Excellent’ rating, a holistic sustainability assessment that is used for projects that meet high standards for minimising environmental impact and energy use. It was also important to Kingsbridge Estates that the site met the Fitwel standard for occupant well-being and health. 

For the flat roof of the extension, Hale Brown wanted a traditional standing seam zinc roof. And like many third-parties, insurers and other architecture firms, it has a strict policy forbidding the use of combustible materials in the external build-up. Mariner Projects needed to design a roof that delivered aesthetics, fire safety and thermal performance. 

Roof regeneration

Working closely with Soprema, Mariner Projects designed the build-up for the roof. Managing Director Tom Mariner explained that “We couldn’t make a real zinc roof fit into the budget, so we worked with Soprema to come up with a solution that performs and looks the part for a fraction of the cost.”

A bitumen layer, Sopravap Vapour Flag, was added to the timber deck before the insulation was installed. “It was critical that the roof delivered the stated thermal performance, so we worked in small, manageable sections to ensure the insulation was protected from the elements,” added Tom.

Once the vapour control layer was installed, Knauf Insulation’s Rocksilk® Flat Roof Slab Extra was mechanically fixed to the deck in two layers to achieve the target U-value of 0.18 W/m2k. The first layer used slabs 95mm thick and the second 105mm to achieve a total thickness of 200mm.

Knauf Insulation’s Rocksilk® Flat Roof Slab Extra was suitable for this application for several reasons. Firstly, its thermal performance meant Mariner Projects were able to achieve the target U-value. Secondly, it’s manufactured with Krimpact® technology, giving it a compressive strength of 90 kPa. This meant the slabs were able to support the weight of the contractors as they worked on adding the membrane and the seam profiles and will support any future maintenance.

“The most significant factor in our decision to use Rocksilk® Flat Roof Slab Extra was its non-combustibility,” explained Paul Booth, Regional Technical Sales Manager, Soprema, “this was critical to us achieving a BROOF(t4) classification. We must align ourselves with suppliers who can meet those standards.”

Rocksilk® Flat Roof Slab Extra is non-combustible, with an A1 Euroclass reaction to fire classification. Roofs are tested as a complete system under TS1187 Test 4 and can achieve one of five classifications, ranging from the lowest FROOF(t4), to the highest BROOF(t4). The test determines the resistance of the complete system to external fire penetration.

Soprema’s Flagon SRDE Membrane was then fixed to the insulation. This membrane is designed to imitate the colour and texture of weathered zinc. To complete the look, standing seam profiles were precisely welded to the membrane.

Paul added that, “Knauf offered full technical support that beats the competition, and they tick all the boxes in terms of product performance. Their support has always been second to none, especially when it comes to fire performance certifications.”

Thermal and fire performance

The Bottle Works project demonstrates how heritage and sustainability can be combined to create inspiring modern workspaces. Hale Brown Architects, Soprema and Mariner Projects collaborated to deliver a cost-effective roofing solution that enhanced the character of the site while meeting strict fire safety and thermal performance standards.

Knauf Insulation’s Rocksilk® Flat Roof Slab Extra played a role in this success, helping the team achieve the non-combustibility and high compressive strength needed for both safety and practicality on site. Tom finished by saying that “Knauf Insulation’s rock mineral wool achieved exactly what the client needed: non-combustibility and thermal performance.”

The site is already thriving and will likely continue to play a role in the heart of Guildford for many years to come.