What role do membranes play in timber frame kits?

Essential repairs and renovation works were 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, working with main contractor Building Bespoke. 

The church was built in 1958 by architect, NF Cachemaille-Day, who designed some of the UK’s most ‘revolutionary’ 20^th century churches, including St Mary’s.  

Andrew Speakman, Director of Speakman Roofing, said: “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. 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.” 

The headline performance characteristics of Proctor Air are its low vapour resistance and its air permeability, but there are other characteristics that also 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 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. 

Proctor Air is an air permeable, low resistance (APLR) membrane. It allows the passage of moisture vapour from the roof space, and 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.