|
Pitched Roofs |
Slates and tiles have been used to waterproof our buildings for thousands of years.
Slates
Tiles
Overlaps
So why not always choose
interlocking tiles?
Which slate should I choose?
Which tile should I choose?
SLATES
Individual 'slates' are hewn from quarried slabs of slate. Slate is a sedimentary rock. It is very strong and is formed over millions of years in compacted layers. Skilled craftsmen are able to split the slabs into individual 'slates' of a consistent thickness. The rock is impervious and durable and, as it is a natural material, slate colour varies even when cut from the same quarry.
Man-made synthetic slates are now available in a number of different materials including fibre cement and resins.
TILES
Tiles are usually moulded. Traditionally this was from clay, which is impervious and once fired, strong and durable.
Man-made synthetic tiles are now available in a number of different materials. The most common of these is concrete.
OVERLAPS
Slates and tiles work in two ways. They are either 'multiple overlap' or 'single overlap'. The latter are usually called 'interlocking'.
Multiple overlapping tiles or slates are less efficient because a greater quantity is required to waterproof a roof. For example a Welsh slate (which measures 60 x 30cm) with a surface area of 1800sqcm only provides waterproofing cover to 42% of that area i.e. 762sqcm. Equally a normal plain tile (which measures 16.2 x 26.2cm) with a surface area of 424sqcm only provides waterproof cover to an area of 166sqcm, 39% of its surface area.
Interlocking tiles, on the other hand, provide greater cover. A double roman interlocking tile with a surface area of 1386sqcm provides waterproofing to 72% of that area, 1000sqcm.
This feature not only reduces the quantity and cost of material required, it also reduces the labour required and, in most cases, it also reduces the load on the roof structure. Be careful here though as tiles generally weigh more than slates regardless of whether they are multiple or single lap and roof loading is a significant factor.
SO WHY NOT ALWAYS CHOOSE INTERLOCKING TILES?
A good question because this is almost always the most economic solution.
Weight & Loading:-
Although interlocking tiles are usually lighter than multiple
overlapping tiles, they are almost always heavier than slates. Therefore
if interlocking tiles are being used to replace slates the load on the
roof frame will be increased. On a typical terraced suburban house this
increase would be 1250Kg! The structure would almost certainly require
strengthening and in such cases we would always recommend that you
sought the advice and recommendations of a Structural Engineer.
Appearance & Planning:-
A change of roof covering can alter the appearance of a house and is
usually a significant factor in its design and styling . Therefore, take
time and consideration. A bad choice could devalue your property. There
may also be planning restrictions if you live in a listed property, a
conservation area or if there are any special local planning
requirements. Restrictions such as these may vary from one local
authority to another, so you must investigate and alert your roofing
contractor to any such limitations from the outset.
WHICH SLATE SHOULD I CHOOSE?
Unless there are very specific planning or heritage requirements, the choice of roofing slate is largely a subjective decision. We recommend that you obtain samples and have a look at roofs which have been re-covered using the slates you are considering. However, here are a few indicators which may help you reach your decision.
Natural slate is by far the most durable. Welsh Slates are purportedly the most durable and are more expensive than imported slate.
Westmoreland Slates from Cumbria and Cornish slates are also available. These are very expensive specialist slates and are usually only used on listed or public buildings or very high specification housing.
Spanish slates are very common but be careful which you choose. The cheaper Spanish slates tend to be irregular and sometime slightly buckled. This can make the slates cock up and be uneven when they are laid. They are less expensive than Welsh slates.
Natural slates are now imported from many other countries including China, Brazil and The United States.
Whenever you are choosing an imported slate be careful about quality. There can be a huge variance and although the quality is generally good, there have been problems with quality in the past. Where possible ask for warranties, which should be available from the supplier.
The most common man-made slates are manufactured from fibre cement with a special waterproof coating. The market leader in the UK is Eternit. These are much more economic that natural slates but have a shorter life expectancy - typically forty years. These are the most common choice for suburban home-owners in Victorian and Edwardian properties.
Resin based moulded slates are more durable such as the Redland Cambrian which has a life expectancy of 60 years. However, resin based slates are more expensive, close to the cost of Spanish slates.
WHICH TILE SHOULD I CHOOSE
Unless there are very specific planning or heritage requirements, the choice of roofing tile is largely a subjective decision. We recommend that you obtain samples and have a look at roofs which have been re-covered using the tiles you are considering. However, here are a few indicators, which may help you reach your decision.
The most common interlocking tile used in London is the Redland49, some times called the 'London Tile'. So called because it was first manufactured in 1949, it is a versatile, strong, low cost concrete product, available in a range of different colours.
There is a vast range of interlocking concrete tiles made by several UK manufacturers. We will be happy to advise you.
Smaller plain tiles are manufactured in clay and concrete. Clay is often preferred in rural environments or where a clay tile is being replaced. However, concrete tile manufacturers have worked very hard to produce tiles that are very similar in appearance to clay.
Both clay and concrete plain tiles are available in a wide variety of different colours and surface finishes. Clay tiles are usually more expensive than concrete tiles.
Hand-made clay tiles give a very rustic appearance. A special hand-made clay tile, curved and conical and originally designed for roofing oast houses, is still manufactured.