Repairs: roofs and rainwater goods

Modern building practices should operate on the principle of ‘built tight; ventilate right’, but specifications do not always pay sufficient attention to the need for ventilation. This results in buildings being effectively sealed, with consequential build-up of moisture.

Solution

Some forms of insulating roofing felts have been recently introduced, but care needs to be taken when specifying. A couple of underlay types were introduced and rapidly withdrawn when found to be comparatively ineffective.

• Ensure that an appropriate grade of breathable fabric has been used for the roof.
• Take care in specifying underlays to ensure that there is a sufficient vapour resistance.