Roof Types & Terminology
The terminology used to describe a roof can sound complicated. Which bit is the gable, ridge or eaves! Do I need to worry about a truss and should I have a barn hip or half hip?
We thought it is time to cut through the confusion and offer a simple glossary guide to the roof options you can find on a timber building such as a garage, studio or stables.
Parts of the core roof structure:
Ridge - This is the very top of the roof. If you look at it as a Ʌ it is the pinnacle right at the top. Along the ridge, you will often place ridge tiles that bridge the gap between either side of the roof.
Eaves - These are the opposite end of the roof to the ridge so the bottom of the Ʌ. The eaves are where the roof meets the wall. When we talk about eaves height, this means the height of the top of the wall and the start of the roof.
Gable - The end of the building, in simple terms this is where the wall rises up to meet the roof and fills the gap in the middle of the Ʌ. We often refer to this as the gable end.
Rafter - Running from the ridge to the eaves a rafter is the core bit of timber that supports the roof and makes the shape of the roof. Timber buildings often use only a rafter and ridge beam roofing system. Larger or wider buildings will need the extra rigidity of a full truss.
Truss - A roof truss is a structure that usually forms a triangle to hold up larger roofs. You will only see them in the finished state but they are made up of purlins and rafters to form a strong and stable supporting structure. Triangles are strong and stop sideways movement spreading the weight of the roof.
Purlin - If you image the rafter runs from the very top of the roof on the ridge to the bottom on the eaves a purlin can be placed about halfway down running from the front of the building to the back (so the same direction as the rafter) and join all the rafters together. The purlin can then be braced back to the centre of the building or ceiling onto the ceiling joist (also called a rather tie) and or centre beam.
Joist - In terms of a roof these are ceiling joists that run from one side of the building to the other (width ways). Not all our buildings have the need for joists as the front and rear walls can act as the joining point between the two sides of the building.
Membrane - A breathable membrane is applied over the top of the rafters (or trusses) which covers the entire roof. This membrane keeps water out but allows air to circulate, circulating dry air helps timber stay in great condition for many years to come.
Gable Roof (also known as an Apex Roof) - a very common front to back or side to side style that is the basic Ʌ structure.
Hipped Roof - Another common type of roof the hipped roof uses a shorter ridge and creates a face at either end coming down to the gable ends.
Half Hipped Roof/Barn Hip - Uses a smaller hip and more gable end. Quite common for carports where it aesthetically softens the roof at either end of the building.
Pent Roof - Often used for garden buildings and studios or where height is an issue. A pent roof is a simple sloping flat roof that has one side higher than the other so water drains off. This roof works well for more contemporary buildings.
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