Product approval & certification

BBA certification is recognised throughout the construction industry as a symbol of quality and reassurance. It's the vital ingredient in the provision of assurance, quality and integrity to a plethora of stakeholders in the construction industry.

SIG Design & Technology

The Project

Project: Plymouth Market

Date: October 2016 – August 2017

Product: Hydrostop AH-25

In 2016, Plymouth Market, the Grade II listed building which is included on the Statutory List of Buildings of Special Architectural and Historical Interest, was found to need a new roof.

The building is noteworthy because of its height and distinctive vaulted roof design, with a main roof area comprising a curved shell formation. Due to this distinct design, re-roofing proved to be more challenging than originally thought.

The Challenge

Over the years, the roof of Plymouth Market had deteriorated, with leaks springing up and holes emerging in the gutters, as well as problems surfacing with heavy leaks from the market’s windows.

Deposits of seagull guano had also built up across the roof area, with its acidic content corroding the membrane.

For the project managers, an important criterion was finding a roofing solution that could achieve the required result but could still allow business to go on as usual. With the initial thoughts revolving around stripping off the original roof membrane by mechanical means, on closer investigations concerns were raised that this would generate excessive stress and vibration that could damage the fragile roof shell.

In addition to this, due to the historic significance of the building, Historic England needs to supervise and approve the refurbishment, in line with historic requirements. This is where SIG Design & Technology (D&T) became involved with their BBA Certified Hydrostop AH-25.

Hydrostop AH-25, a one-component product which offers advantages over other PU and PMMA systems and has a warranty for up to 25 years, offered a very low in odour and fast-curing, fully reinforced membrane with a polyester fabric.

With such a large and complicated steep-sloped curved roof with difficult access, the Hydrostop AH-25, which can be applied under practically any conditions including temperatures as low as 00C, proved ideal for this type of large commercial project.

Adding to the challenge of the size and steep-slopes – which is in direct contrast to typical flat roofs – SIG needed to ensure that the Historic England requirements were met by manufacturing AH-25 in a Weathered Silver, which is in keeping with the buildings current appearance, but doesn’t compromise the quality of their BBA Certified product.

With state-of-the-art buildings incorporating new designs developed for their aesthetic value as well as the comfort of their inhabitants, Schöck provide products that give real peace of mind to building innovators concerned about heat loss and designing energy efficient buildings.

Despite the excellent pedigree that Hydrostop AH-25 has, SIG Design & Technology still chose to have this product Certified by the BBA because, according to Mike Crook Trading Director – SIG Design & Technology,

BBA Certification provides confidence and product reassurance for architects and other construction professionals when specifying products, and it is important to have an industry leading impartial body give the necessary assurance that our product is fit-for-purpose.”

The Result

With its paint-on system, AH-25 proved to be the ideal product for the repair of the unique wave form main roof, as well as being used in tackling repairs to two smaller canopy roofs at the market.

Julie Boyes, Contracts Manager at Ryearch Limited, commented: “The application of AH-25 created less noise and disruption than using another solution. Our client Plymouth City Council were very pleased with the finished results of the work and having the assurance that it had been certified by the BBA provided us with additional comfort.”

Rob Lazarus, Contracts Manager at Clegg & Shortman, employed by Ryearch to complete the works stated, “It was the perfect product for the job…and so easy to use.”

For more information please contact:

SIG Design & Technology
Tel: +44 (0) 1509 505 714

The master certificate holder is KVT Dichtungssysteme GmbH, telephone 00 49 4101 38307






Bespoke colour, Weathered Silver as requested by Historic England

SIG_Plymouth_Market_01 rev1


Solution allowed trade to continue while roofing work was in progress

SIG Plymouth Market 15a


Avoided the need to strip the original membrane from the fragile roof shell

SIG Plymouth Market 14


Access to this large and complicated steep-sloped curved roof was very difficult

SIG Plymouth Market 12

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