Slate is a fine grained, metamorphic rock, derived from a sedimentary
rock composed of clay or volcanic ash, and metamorphosed by heat and
Slate is a popular roofing
material, as it is strong and waterproof. It is also convenient
to shape into the standard rectangle shape as used on roofs, as
it has two lines of breakability cleavage and grain, making it possible
to split slate into thin sheets, ideal for roofing.
Slate roofing is also
highly durable, thanks to its chemical stability and thermal stability,
thus it is less susceptible to environmental factors. Slate roofs
can last very long periods of time as a result.
Tiles are manufactured materials made from hard wearing materials
such as ceramic, clay, stone or even glass (though this depends
on the use of the tile, as tiles are not used exclusively for roofing).
Roof tiles are usually made from clay, though they can be made from
slate or wood (known as shingles). Sometimes, modern materials such
as concrete or plastic are used, though clay is still most common.
Clay tiles will often have a waterproof glaze.
Tiles have been used
in roofing for centuries, and thus several different shapes (or
'profiles') have evolved.
Flat roof tiles are the simplest type of roofing tile. As the name
suggests, they are flat, and they are usually a rectangular shape.
When placed on a roof, they are usually layered, and are laid in
a repeating, parallel pattern. Flat roof tiles are usually made
from wood or stone, though the design is also used for solar panels
when used in roofing.
Flat tiles were once
limited by an Act of Parliament to a regular size of 10.5 by 6.5
inches. This act has long since been repealed, but the size has
remained constant, apart from a slight change to 265 by 165mm in
the mid 1970s. Methods of laying tiles have remained surprisingly
Modern tiles have a 'nib',
which allows them to be hung from battens (the horizontal pieces
of wood which traverse the rafters)
Roman tiles are flat in the middle, with a convex curve at one side,
and a concave curve on the opposite side, allowing them to interlock.
Single Lap tiles (or pantiles) have a shallow, 'S' shaped profile,
allowing adjacent tiles to lock. When laid, they form a pattern similar
to a ploughed field. The size of a single lap tile was fixed in the
early eighteenth century at 131/2" x 91/2". One of the main
disadvantages of a single lap tile is the shape, which can make the
cutting of the tiles to fit a 'hip' or a 'valley' on a roof. The underside
of a single lap tile is usually torched with a lime or a clay mortar,
to prevent rail or snow penetration.
(or Barrel) Tiles
Mission/Barrel tiles are semi-cylindrical tiles, traditionally made
by forming clay around a log. The tiles are then laid in an alternating
concave/convex pattern. These tiles are common in France, Spain and
Italy, particularly in rural regions.
Peg tiles are very similar to flat tiles, with one obvious difference,
in that they have holes through which an oak peg is pushed through,
holding the tiles together. The roof can be very colourful, as moss
growths can occur, and tiles when replaced will often be a different
shade to the majority of the roof. Modern day pegs tend to be made
from steel or aluminium rather than oak.
Felt roofs are made from a rigid urethane or phenolic insulant,
which is laminated onto a solid roofboard.
A felt roof is applied
to a baseboard, which is coated with a preservative. This is to
help maintain the condition of the baseboard for longer. Lay the
felt roofing over the baseboard and secure it using clout nails,
ensuring the material is laid smoothly, with no air bubbles. Over
the first layer, paint bitumen mastic over the layer before applying
the felt layer flat. Using a soft brush, try to remove any air bubbles.
Depending on the strength of the roof, you may be able to walk on
any air bubbles to remove them. Any gaps should be painted with
bitumen mastic to aid waterproofing. Finally, apply the third layer
in the same way as the second. Apply another coating of bitumen
mastic over the entire surface, before scattering a chipping compound
of limestone, granite or gravel, across the roof. This helps strengthen
the surface, and also helps to reflect sunlight, protecting the
Felt roofing is usually
used for flat roofs. Many homes can have certain areas with a flat
roof which requires felt roofing, as tiles are not effective on
a level surface. Garages and pre-fabricated buildings regularly
use felt roofing as it is cheaper and easier to apply then tiling.
It is also common on garden sheds, due to the light weight construction
This is a cheap method of roofing, used mainly in military installations
and farm outbuildings due to its low cost and strength. Corrugated
Iron can also be transported easily, due to its regular shape.
houses do use corrugated iron in their construction, typically more
remote homes in Australia and the United States, with a number of
developing countries beginning to use it in construction as it is
cheap and easily obtainable.
Thatching is the art of covering a roof with vegetation such as
straw or rushes. It is one of the oldest roofing materials, and
has been used worldwide. It is still employed in a number of third-world
countries, as well as in a number of Western European homes. However,
thatching is no longer a low cost method of roofing, as costs have
increased considerably over the previous 40 years.
Thatching is a high quality
material, and if installed by a skilled thatcher, can last over
50 years, though this is subject to the material used, as certain
types are better suited to specific climates. Traditionally, a new
layer of thatching was applied over the existing layers, which has
left some old thatched buildings with thatched roofs over 2 metres
The obvious danger of
a thatched roof is that of fire. Thatched roofs do not catch fire
and more frequently than normal roofs, however the risk is that
once alight it can be very difficult to put out. If the chimney
of a thatched house is of poor quality, and gases or sparks escape
into the roofing then fire does become a greater risk. As a result,
many insurers won't insure a thatched home, and the few that do
will charge high premiums, as they are aware that buyers have no
Thatched roofs are coming
back into fashion at the moment, as an environmentally friendly,
and sustainable, material.
Thatched roofs are banned
in the City of Barnet, since the Great Fire of Barnet in 1666. The
law remains in place today, and there is only one exception to the
rule the replica of the Globe theatre.