A high-performance roofing membrane from Icopal has been used to help solve the long-standing damp problems of a medieval castle in Cumbria.

Almost 200m2 of Icopal’s vapour permeable Monarperm 700 has been installed under the slate roof of the 16th Century south wing of Sizergh Castle near Kendal as part of a £1.4 million restoration which includes major reroofing and repairs to the castle structure.

Icopal’s BBA-certified lightweight membrane was specified by Purcell Miller Tritton for the roof of the library and chapel of the castle, where the Strickland family have lived for more than 700 years, in a joint-funded English Heritage and National Trust project.

Set in the picturesque border of the Lake District, the castle comprises a castellated tower and was built in the 14th Century, with substantial additions in the 16th century. It has re-mained open to the public throughout the refurbishment which has seen some 43 miles of scaffolding erected with overhead plastic sheeting protecting the inner roof sections and the remarkable interior decoration which features lavish use of oak carving.

The work is part of a two-year scheme to repair the roofs of the north and south wings, central roof tower, parapets, gutters, chimney stacks, garden steps and east wall of the castle, with main contractor Cox & Allen using local materials and traditional techniques similar to those used when it was first built.

Locally-sourced Westmorland green slate, sheep’s wool loft insulation and traditional lime-based mortars were among the materials used during the restoration which also included large scale re-pointing and re-rendering of high-level walls and stacks.

After identifying the extensive necessary repairs, Purcell Miller Tritton met with the Na-tional Trust, English Heritage and local planning authorities to agree on materials, appear-ance and strength, ensuring work could begin on the Grade I listed building with no objec-tions.

Kenny Brown, of Purcell Miller Tritton, who specified the product and has used Icopal ma-terials on a number of projects before, said: “The refurbishment involved carrying out nec-essary repairs to the building fabric of which the re-roofing works played a large proportion due to the scale of the north and south wings.

“Our local Icopal rep visited our office to advise us on an appropriate product to use as an effective waterproof membrane and so we specified Monarperm 700 as a necessary sec-ond barrier to achieve water tightness.”

Extra care had to be taken not to disturb the castle roof’s bat population which was no doubt camouflaged by the anthracite underside of the Monarperm 700 which also helps to blend in with the aged colours of the property. It is complemented by a Monarflex eaves guard system that is dressed into the gutters.

Margaret Reid, National Trust house manager at Sizergh Castle, said: “It’s exciting for staff, volunteers and visitors to learn more about the nuts and bolts of the building. It’s not every day you have the privilege of seeing a historic building stripped right down to the roof timbers. There’s the satisfaction of knowing we are working to preserve the castle for future generations.”

Phase two of the reroofing work will see a further 350m2 of Monarperm 700 installed in the north wing which formerly housed an enormous Tudor kitchen. This area is not open to the public.

Email: info.uk@icopal.com