Most roof tiles in the United Kingdom are manufactured from either clay or concrete, materials that are both heavy and prone to frost damage.
Both of these tiles can add significant amounts of weight to the roof structure and on many homes they contribute to “roof sag”. That is where the centre of the roof structure dips under the increased load. This usually occurs after several years and is also more noticeable in areas that are subject to prolonged snowfall. Roof sag is quite normal and doesn’t necessarily mean a re-roof is required.
Below are some lightweight alternatives to traditional clay and concrete tiles. Please remember that if you are replacing lightweight tiles with a heavier variety, you must consider the implications and possibly install extra rafters or roof timbers to accommodate the additional load.
Slate itself is quite heavy but roofing slates are cut thinly and cover a large area. A typical roof will weigh over 20% less if slates were used instead of concrete tiles.
There are a wide variety of slates to choose from. Cheap foreign imports from China have a similar life expectancy as the more expensive and traditional Welsh variety. There is also a choice of colours and shades.
Artificial or man made “synthetic” slates are also available. These are usually slightly lighter and cheaper but are not as aesthetically pleasing and normally have a much shorter life expectancy.
2) Lightweight Metal Roof Tiles
If you are looking to install lightweight metal tiles then choose something like the Decra steel sheets (see photo to the right). They are manufactured to look just like traditional tiles and come with a coated finish, usually with coloured minerals adhered to the surface.
As an added bonus, most of these metal tiles are not only lighter than traditional clay or concrete but also last longer and can be used on much more shallow roofs. For more information, see my guide to roof tiles for shallow roofs.
Because they are made from thin metal, they are easy to damage and dent. Branches and other falling debris can easily punch through the surface while a concrete tile may be a bit more resilient.
Shingles can be made from either traditional wood or from the much more modern bitumen (oil based).
Both are considerably lighter than concrete or clay but both have a shorter life expectancy and wooden shingles require more maintenance and are typically used on period homes.
Bitumen based shingles are very cheap to manufacture and simple to lay. They are popular in Canada and the United States but are rarely seen in Europe.
Both wooden and bitumen shingles have a shorter life expectancy than clay or concrete tiles.
Heavy Concrete Tiles
Concrete tiles are by far the most popular in the United Kingdom. A roof that has the correct number and sized rafters shouldn’t suffer from any structural problems. Issues usually occur when replacing a roof and choosing heavier tiles.
Although concrete tiles are heavy they have a long life and are fairly cheap to purchase and easy to source, unlike some of the more modern lightweight tiles. Lack of demand usually means higher costs and limited availability.