Roofs
The purpose of a roof is to keep out water and to prevent the deterioration of the building and its contents. In order to fulfil its role of protecting the building the roof needs to be carefully maintained in order to retain its weatherproof properties.
Maintenance
In addition to the regular inspection and cleaning of the rainwater goods and drainage, it is important to check the roof twice a year. Most roofs are very complex and can include concealed gutters and parapets which hide parts of the roof if viewed from the ground. The inaccessibility of the roof poses the greatest problem, as defects and damage are not easily detected.
Moss should be regularly brushed off the roof to prevent a build-up. It detains moisture and damp which can lead to the lamination of slates and tiles. Rainwater on moss- or lichen-covered slate or tile roofs results in an acidic run-off which can cause holes or channels in metal coverings.
Figure 1 Moss on a tile roof
If localised repairs have become necessary these should be executed as soon as possible to prevent further damage. Loose slates and tiles should be refixed and broken ones replaced. Patch repairs and replacements on lead roofs should be welded, not soldered, by a qualified contractor and with due respect to fire precautions. Likewise, localised repairs of thatched roofs should be executed in matching materials by an experienced thatcher.
Some metal roof coverings like copper, stainless steel and aluminium are very light and prone to wind damage. In this case, the coverings require immediate refixing and, if damaged, possibly complete replacing.
Repair
Undetected damage to the roof can very quickly lead to water ingress, damp, rot and insect infestation. Water stains on the interior walls, damp and moss-covered exterior walls, slipped and broken slates and tiles or vegetation growth in the gutters are signs that the roof requires urgent attention. Your inspecting architect will be able to assess the damage and advise you on the necessary steps.
Figure 2 Decayed rafter feet ready for repair in the roof of St Katharine's Chapel, Well Cathedral (© Ian Harper, English Heritage)
If roof damage is identified early, only a few localised repairs may be necessary. However, if damage is undetected or untreated for too long it can lead to serious problems and might require major repairs to the rest of the fabric, as well as the complete recovering of the roof.
If this has become necessary it is important to reuse as much original material as possible. Any new material should match the existing covering material in type, size, thickness, colour and texture. The use of substitute materials such as resin slates or artificial stone slates is not recommended.
It is also advisable to photograph the old roof before stripping it, in order to provide a record of the detailing which should be reinstated in the repairs.
The addition of felt underlays, bitumen-coated fabric or spray-on coating to any kind of roof is not recommended as they inhibit ventilation to the roof space and can provide the necessary conditions for a fungal attack. Bitumen-coated fabric applied on the outside of the roof covering can obscure defects and prevent the re-use of intact tiles and slates.
Health and Safety
Roofs can be highly dangerous and no inspection should be carried out without appropriate risk assessment and safety devices. Roofs are generally not designed to be walked on. Slates and tiles are brittle and can easily be damaged; metal coverings can also be punctured and split.
Ask your inspecting architect for advice on accessing your roof for regular inspection.
You can also find further information on Health and Safety under Health and Safety and Working at Height.
Metal Thefts and Roof Replacements
High metal prices have caused a dramatic number of roof thefts, causing immense damage. Ecclesiastical Insurance has published a guidance note on security measures to prevent the theft of your church roof and on replacement options. For further information, please see the Theft of Metal page on this website.
November 2007
Further Information
SPAB, Technical Q& A 15: Roof Maintenance (available on the SPAB website)
Please also see the information on metal theft and security measures on Ecclesiastical's website.
