Repairing Roofs in an Older Home
Common roofing materials
Before the development of railways and canals in the early 19th century, roofs were made of whatever was locally available - stone slates, clay tiles, straw for thatching. With the growth of transportation systems materials such as Welsh slate were moved all over the country. The roof is often a key element of an older home's character and significance.
If you want to make repairs to your roof you may need permission and should seek advice, especially if your home is listed or in a conservation area (see Who Do I Contact?).
Pitched roof coverings
Slate and stone finishes
Slates can last longer than any other roof covering before needing repair. Once a number of slates start to fail it makes sense to strip the whole roof to make sound and worthwhile repairs. It is important to retain features such as slate sizes, number of courses and overlap, method of laying and bedding - particularly where stone slate is used.
Slated roofs can become 'nail sick' with age. This is where the nailheads begin to decay and movement caused by weathering means that the nail holes get bigger and the slates start to slip. Lead, copper or zinc 'tingles' or clips are useful for re-fixing the odd slate.
Traditional tiles made of clay are still widely available in a variety of sizes. Less common tile types are available from specialist manufacturers. Tiled roofs need little attention beyond checking for any dislodged tiles, particularly following a storm. Signs of failure include spalling (flaking) and breakage. Remove any affected tiles and check them carefully - you may be able to reuse them. If you are going to retile a roof it's common to renew the timber battens to which the tiles are fixed at the same time.
If the tiles are large or single lap they will cope less well with any curve or sag in the roofline. You may need to add packing if the purlins (the beams that help support the rafters) are sagging so as to maintain a suitable line for the tiles.
Maintenance and repair issues are similar for all kinds of thatch, whether straw, water reed or heather. Ridges, gables, and chimney abutments are usually the first areas to show signs of wear. The ridge may need to be recapped even while the rest of the roof's coating is still in good condition. Wire netting over the ridge can prolong the life of the thatch by keeping the material in place.
As the thatch ages it attracts moss, algae and fungi. This is often worse where trees overhang or restrict airflow over the roof. A good maintenance routine should include raking down of the roof to remove growth and debris.
Traditionally, straw thatch was repaired piecemeal and only fully overcoated when necessary. After a number of these recoats thatch becomes too deep and heavy for the supporting timbers. At this point it will have to be stripped back to a sound coat, or even to the basecoat, and rethatched. Basecoats can be extremely old and can contain much historic information so these should be retained wherever possible. You may need permission to remove them completely and should seek advice, especially if your home is listed (see Who Do I Contact?).
If you need to make repairs to your thatched roof check with your local planning authority first. It is likely to have a policy concerning the thatch types that are appropriate for your region.
Flat roof coverings
Many older buildings have areas of flat roof, typically over porches, dormers, extensions and towers.
Lead is the most common sheet metal material in flat roofs. It was traditionally made by casting, but with later manufacturing techniques became rolled sheet lead.
Metal expands and contracts with changes in temperature, so lead and other forms of metal roof are made up of panels with weather-tight seams that allow some movement.
Repairs to lead and copper sheeting require the services of a metal roofing specialist. Pinholes in lead caused by corrosion can be patched, as can splits caused by thermal movement.
Flashings are used to weatherproof the junctions between the roof covering and wall abutments such as chimneys and parapets. These junctions are often the most vulnerable part of the roof. They need regular inspection and any problems should be dealt with promptly. If in doubt seek advice from a professional with experience of older buildings. Lead is the most common and effective type of metal used for flashings.
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