Case study: reroofing of St Mary’s Barton

Essential repairs and renovation are being carried out on a parish church in Oxfordshire, as part of which St Mary’s Barton is receiving a new pitched roof covering and underlay. The roofing work has been carried out by contractors Speakman Roofing, who were invited to tender for the project by main contractors Building Bespoke.

While the church is not particularly old compared to some, having been built in 1958, it possesses architectural significance. The architect, NF CachemailleDay, designed some of the most “revolutionary” 20th-century churches in the UK, including St Mary’s. The reroofing works, therefore, had to be specified and carried out respecting the architectural heritage of the building.

The church’s pitched roof specification was the responsibility of the roofing contractor, and Speakman Roofing put forward Proctor Air® as their referred underlay.

“We use Proctor Air on nearly every project. The feedback from our installers is that it’s good to use. It gets all the little things right that matter to the people using it.”

– Andrew Speakman – Director, Speakman Roofing

Feedback on the positive and negative aspects of a construction product, like a pitched roof underlay, can significantly alter how that product (and its manufacturer) is perceived in the marketplace.

Speaking on this topic on the Proctor Podcast, Will Jones, Head of Business Development at Proctor Group said: “Third party certification provides confidence that a product does what it says and can be used in a certain application. But you can’t appreciate a product until you’ve tried and tested it. There’s nothing better than using a product in the field. How did it perform? Were there any problems with it?”

Feedback from end users is crucial. If a product is difficult to install, even for an experienced contractor, then the manufacturer needs to understand that. Otherwise, contractors will complain to their merchants and suppliers, and simply move on to an alternative they prefer. Or the feedback might reach the architect and the product simply doesn’t get specified again.

“At Proctor Group, we pride ourselves on making products that are fit for purpose,” said Sales Director John Johnston in the same podcast episode. “Contractors sometimes speak to us about cheaper alternative products they’ve had a bad experience with, and we carry that feedback into our product development processes.”

At St Mary’s Barton, Speakman Roofing chose Proctor Air because they were already using it. As Director of Speakman Roofing, Andrew Speakman, explained: “We use Proctor Air on nearly every project. The one product can cover all eventualities so it’s cost effective – we don’t have to stock different rolls of different membranes.”

A cost effective product is not the same as the cheapest product, and one of the big reasons for Proctor Air being cost effective is that Speakman Roofing’s team like using it and know it works.

“From the first time we trialled Proctor Air, the feedback from our installers was that it’s good to use,” said Andrew. “It gets all the little things right that matter to the people using it.”

Practical questions about a pitched roof underlay that matter to installers include: does it tear easily? Will it cut well, or do the edges fray when you run a knife through it? Andrew Speakman described how his installers found Proctor Air to be “lightweight but strong.”

The headline performance characteristics of Proctor Air are usually its low vapour resistance and its air permeability, but there are other characteristics that make a big difference to installing it on site. For example, in an assessment of the fabric’s strength, Proctor Air achieves an excellent Mullen burst strength result. This helps it to resist normal roof installation loads. In addition, an assessment of its slip resistance shows it has a high coefficient of friction, which increases safety during the installation of the covering as part of normal safe working practices.

Of course, a pitched roof underlay has to deliver its promised performance for the building as well. Proctor Air is an air permeable, low resistance (APLR) membrane.

• Air permeability provides consistent ventilation and a more uniform flow of air from a cold roof space compared to normal vents. It also means that no vapour control layer is required in the ceiling.
• As one of the highest performing vapour permeable membranes available, Proctor Air allows the passage of moisture vapour from the roof space. It has an Sd value of 0.015m and a vapour resistance of 0.075 MNs/g.

This combination of features reduces condensation risk in the roof space while avoiding the need to install vents in the roof – which is especially useful on heritage projects and existing roofs.

“The air permeability of Proctor Air makes it very versatile for us,” said Andrew Speakman. “St Mary’s Church featured a traditional pantile on a mortar-bedded creasing tile eave. Proctor Air gave us a breathable roof without sacrificing the traditional elements, and while maintaining the original appearance of the building.”