Repair or Renew the Roof in an Older Home
While providing essential shelter from the weather, the roofs of older homes are often an important part of their historic significance too.
What roofs reveal about a home's history
The roof is often a key element of an older home's character and historic interest.
Roof coverings
The material used to cover old roofs varies widely depending on where you live and can provide clues to the age of your house.
Before the development of railways and canals in the early 19th century, roofs were made of whatever was locally available such as stone slates, clay tiles, straw for thatching, and some leadwork.
With the growth of transportation systems, materials like Welsh and Cumbrian slate became available all over the country.
Roof structure
The roof structure is the part that supports the covering. In many old houses, this is one of the most important features. Many historic roof structures have survived for well over 100 years, and it’s not unusual for Georgian-looking houses to still have medieval roof timbers.
Old roof structures, generally in oak or elm, are interesting for their structural carpentry, the nature of which changed over time and may tell us how old a building is. Some may also have interesting carved details and carpenters’ marks.
Gallery
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Repair or renew? What to consider before you decide
Keeping the rain out is the first priority, so if your roof needs repairing, act quickly.
But replacing an old roof covering is disruptive and expensive, so first check whether it is repairable.
Damp can be caused by repairable faults like a leaking chimney or lead flashings, or by slipped slates or tiles. Other faults may be repairable too. Below we introduce the issues you might encounter and some of the solutions to consider.
Structural timbers
The priority should be to keep your existing roof structure and avoid replacing old roof timbers. The most important of these are the roof trusses and the purlins (the horizontal sidebeams that support the rafters).
Good joiners can repair historic timbers if rot has damaged them. It is usual to put in new battens (the thin horizontal strips of wood that the slates or tiles are fixed to) if the roof covering is being replaced, but it’s rarely necessary to replace the rafters.
Slate and stone roof coverings
Slates can last longer than any other roof covering before needing repair.
Nail sickness
In some old houses, so-called ‘nail sickness’ can occur. This is where the nailheads begin to decay and movement caused by weathering results in the nail holes getting bigger and the slates starting to slip. This corrosion of the nails that hold them does not mean you need to replace the whole roof. Lead, copper or zinc 'tingles' or clips are useful for re-fixing the odd slate.
When slates fail
Once a number of slates start to fail, it makes sense to strip the whole roof to make sound and worthwhile repairs. With care, it’s often possible to re-use a high percentage of the covering, making up the difference with new slates.
Keep existing roof features
Try to keep the existing roof ridges. It is important to retain features such as slate sizes, the number of courses and overlap, and the method of laying and bedding, particularly on stone slate roofs.
Tiles
Tiled roofs need little attention beyond checking for any dislodged tiles, particularly following a storm.
Failing tiles
Signs of failure include spalling (flaking) and breakage. Remove any affected tiles and check them carefully. You may be able to reuse them and should try to keep the existing roof ridges where possible.
Retiling
Traditional tiles made of clay are still widely available in a variety of sizes. Less common tile types are available from specialist manufacturers. If you are going to retile your roof, it's common to renew the timber battens the tiles are fixed to at the same time.
Sagging roofline
If roof tiles are large or single lap (where the overlap between tiles is just along a narrow strip at the edge) 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 to maintain a suitable line for the tiles.
Thatch
Maintenance and repair issues are similar for all kinds of thatch, whether long straw, water reed, combed wheat reed or heather.
First signs of wear
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.
Maintenance and repairs
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.
Local thatch types
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. We recommend that you use the material and methods typical for your region, especially if your house is listed.
Re-thatching
After a number of overcoats, thatch becomes too deep and heavy for the supporting timbers. At this point it needs to be stripped back to a sound coat, or even to the basecoat, and re-thatched.
Basecoats can be extremely old and can be an important part of your house’s archaeology so we recommend keeping the lower layers where possible. You may need permission to remove a basecoat completely, especially if your home is listed. Before re-thatching, you should get advice – refer to the section on getting help, advice and permissions below.
The Society for the Protection of Ancient Buildings (SPAB) also provides guidance on thatched roofs and repairing timber roofs.
Sheet metal roofs
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.
Pinholes in lead caused by corrosion can be patched, as can splits caused by thermal movement.
You will need to find a metal roofing specialist to carry out repairs to lead and copper sheeting.
Gallery
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External features and flashings
The external roof features, whether functional or decorative, also make an important contribution to your home’s character.
Chimneys and pots
Keep chimneys and pots, even if you no longer use them, and check them as part of your regular maintenance checks.
Chimneys can still help with ventilation during warm weather and in winter you can use a damper or chimney balloon to reduce draughts.
Ridges and finials
Keep details such as original clay or stone ridges and decorative finials. Carefully remove them during work so that they can be refixed later.
Flashings
Flashings are usually made of sheet lead. They weatherproof the junctions where the roof covering meets an abutment such as a chimney. These junctions are often the most vulnerable part of the roof.
Inspect them as part of your regular maintenance checks and fix any problems quickly. If in doubt, get advice from a professional with experience of older buildings.
Gallery
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Get the help, advice and permissions you need
Before re-covering your roof, we recommend you get independent professional advice from an architect or surveyor with experience of old buildings. At the very least, find a roofing contractor who understands the particular nature of old roofs in your area.
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Check what permissions you may need
If your house is listed, you will need consent to change the roof’s shape, height, pitch, internal structure or type of covering, or to add a rooflight window. In conservation areas, you may need planning permission, so check with your local authority.
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Who do I contact?
This page describes the key points of contact and sources of advice if you are thinking of making changes to your home.
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Where to find specialist help
Seek independent professional advice from an architect or surveyor with experience of old buildings, or at least find a roofing contractor who understands the particular nature of old roofs in your area.
