Pitched roofs are the most common types of roofs found on buildings. They are most often used because they effectively shed water, whereas the other type of roofs, such as a flat roof, aren’t. A pitched roof is most likely to be found on the main buildings on most domestic properties.
Types of Pitched Roofs
Anyone who knows about roof construction will tell you that the highest quality roofs will be from 1900-1914. Shortages of material and rationing of wood in the 1945-54 period meant that there was typically poor roof construction. Modern truss roofs started to become more common up to 1970 and are now the only type of roof construction commonly used in the UK.
Here are the different types of pitched roofs:
- Lean-to or mono-pitch roof: This is the simplest form of roof generally used for small extensions. It should only span a short distance.
- Couple roof: This is a simple roof that includes the rafters and the ridge beam. But it is rarely used nowadays as there is no lateral support; this can lead to roof spread and other defects. A collar roof is more often used, bringing us to our third type of pitched roof.
- Collar roof: This is a simple roof with a collar to prevent roof spread. However, despite being more popular than the pitched couple roof, the collar roof is rarely used for roofs as it has a max recommended span of 4.5m.
- Perlin roof: Collared or coupled roof where there are purlins.
- King post truss roof: This has additional supports in terms of the king post and the struts, as seen below, and is often used where a more extensive span is needed.
- Mansard roof with king/queen post: This is a pitched roof with an additional pitch and is often used when space is needed within the roof.
- Modern Truss roofs: These pitched roofs have webs as bracing and are prefabricated in a factory. They are easy and efficient to install as no specialist carpenters are needed when installed. These have become the norm in modern roof construction.
Damp Penetration in Pitched Roofs: What Else You Need to Know
- In solid walls, timber or steel is built into the adjacent structure; there must be a sufficient thickness so that the solid wall can work in the way it was designed. A solid wall is designed to be permeable. When there is rain, the wall’s outer section will be saturated and will then shed water. The saturated area of the wall will then dry when the rain stops. Otherwise, damp penetration through the wall can reach the timbers and steel where the covering lack thickness.
- Gutters must be the appropriate size for the size of the roof. Calculations can be made depending on the size of the roof and average rainfall. The gutters can then be adjusted for this.
- Inadequate pitch: This depends on the covering. Some coverings can shed more water at a lower pitch; some must have a steep pitch. Too low a pitch and the rain will not runoff. A roof with a low pitch can also suffer from wind damage.
- Gauge and lap problems: Tiles must overlap each other to a degree to which there is no moisture ingress; this will also depend on the roof covering. However, if there is too much of an overlap, this will result in additional unneeded load to the roof structure, leading to bowing and damage to the roof structure.
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