Roofing Terminology


The portion of the roof projecting out from the side walls of the house.

Counter Flashing
The flashing which is embedded at its top in a wall chimney or other vertical structure and is lapped down over tiles,slates flashing.

Horizontal rows of slates or tiles.

The lower edge of a roof (usually overhanging beyond the edge of the house).

Trim Board behind the gutter and eaves.

Sheet lead or other material used at junctions of different planes on a roof to prevent leakage.

usually a breathable membrane for pitched roofs or polyester based for flat roofs..

The triangular upper part of a wall closing the end of a ridged roof

The external angle at the junction of two sides of a roof whose supporting walls adjoin.

In a flat roof, a horizontal structural member over which boarding is nailed.

A structural member (usually slanted) to which battens are nailed.

The slanting edge of a gabled roof extending beyond the end wall of the house.

The horizontal line at the top edge of two sloping roof planes.

The number of inched of vertical rise in a roof per 12-inches of horizontal distance. Also referred to as pitch.

The boards that enclose the underside of that portion of the roof which extends out beyond the sidewalls of the house.

The less-than 180-degree angle where two sloping roof sections come together.

Valley Flashing
The flashing in valleys, extending in under to tiles/slates on both sides.

 Built-up Roof
A low-slope (or flat-seeming) roof covered with alternating layers of roofing felt and hot-bitumen and topped off with a layer of mineral felt or solar paint..


Slate Roofing

types of roofing

Slate is a fine grained, metamorphic rock, derived from a sedimentary rock composed of clay or volcanic ash, and metamorphosed by heat and pressure.

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.

Tiled Roofing

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 Tiles

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 unchanged also.

Modern tiles have a 'nib', which allows them to be hung from battens (the horizontal pieces of wood which traverse the rafters)

Roman Tiles

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

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.

Mission (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

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.

Corrugated Iron

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.

Some 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.


  • Flat roofs are not actually flat but are built on a slight incline to prevent ponding (accumulation of water). Materials used in flat roofing need to be water resistant and watertight. Flat roofs require regular inspection because damage is not visible until there is leak. The five main types of flat roofs are roll asphalt, single-ply, multiple ply, modified bitumen and flat-seamed metal.

    Roll Asphalt

  • Roll asphalt has been used in flat roofing for more than 100 years. This type of roof consists of layers of asphalt-coated fiberglass felt, tar and water resistant materials, which are kept in place by nails or asphalt cement. The topmost layer is covered with gravel or crushed rock, which serves as a counterweight and provides protection against ultraviolet rays from the sun. It is the cheapest kind of flat roof, but it generally doesn't last more than 10 years.


  • Single-ply flat roofs are made from a single layer of materials that have properties similar to rubber or plastic. These materials offer a less expensive, but sturdier and more energy efficient, alternative to roll asphalt flat roofs. The most commonly used modern materials in single-ply flat roofs include ethylene propylene diene monomer (EPDM), polyvinyl chloride (PVC) and thermoplastic polyolefin (TPO). These materials are preferred because they are mold resistant and generally maintenance-free. On average, single-ply roofs last 10 to 12 years, although TPO roofs may last as long as 30 years.


  • Multiple-ply roofs, also called built-up roofs, are made of a number of layers of fiberglass felt packed between layers of water-resistant asphalt. In comparison to single-ply roofs, multiple-ply roofs are thoroughly reinforced, which means that they last longer and are less prone to damage. The average lifespan of a multiple-ply roof is between 10 and 30 years.

    Modified Bitumen

  • Some multiple-ply roofs make use of a modified bitumen membrane, which is made from a mixture of polymers and asphalt. The modified bitumen membrane has the flexibility of polymers and the water-resistant characteristics of asphalt. The topmost layer is covered with a reflective material, gravel or mineral blends. Modified bitumen flat roofs last between 10 and 20 years.

    Flat-seamed Metal

  • Flat-seamed metal roofs are more expensive than other types of flat roofs because they are made from metals, such as copper and stainless steel. Metal roofs are lighter than other types of flat roofs, which make them an excellent choice for buildings in areas with high seismic activity. Depending on weather conditions, metal roofs last between 20 and 50 years.
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