With so many self-build projects underway at the moment, it helps to understand the various types of roof. In this blog, Christopher Morley answers a few common questions surrounding pitched roofing.
Here at The Metal Roof Company, a question that we are often asked is “what is meant by pitched roofing?” Put simply, a roof pitch refers to a roof that has a downward slope either in one direction (Known as a Monopitch roof, see image 1 below) or a Duopitch roof, which has slopes in two directions with a ridge at the highest point (image 2 below).
In the UK, a Duopitch roof is the most common type of roof because it offers a good degree of weather protection and allows water to quickly drain away.
Image 1 ^ : Monopitch roof with standing seam metal supplied by The Metal Roof Company. Planning conditions dictated that the metal roof remained unobtrusive and subtle, thereby enhancing the valley view. Click here for full project details of the Grand Design Cornwall Project.
Image 2 ^ : This is a Duopitch roof with standing seam metal roofing supplied by The Metal Roof Company. The higher ridge really added to room size. Click here for full project details of the West Country New Build Project.
So, what is a low-pitched roof?
Roof pitches under 15° are referred to as flat or low pitch roofs. Roof height is often a condition of local planning restrictions and necessity for a low or flat roof will affect the roof volumes. It will also mean more rain will run off the roof, hence correct gutter and downpipe sizing need to be considered. The Metal Roof Company can advise on the correct gutter size for the style of roof here. Certain standing seam metals such as Copper, Zinc and Aluminum are not suitable for flat or very low-pitched roofs. In such instances, manufacturers should be consulted.
What is a Monopitch roof?
A Monopitch roof slopes downward in one direction only. This roof design ensures that space and light is enhanced on one side of the building. See above.
Measuring roof Pitch:
The steepness of a roof needs to be described in a precise and measured way. The standard method is measuring in angle degrees, somewhere between 0° (flat) and 70° (in the UK. Regulations state that any roof above 70° is effectively a wall). In-reality, a totally flat roof is rare, since a slight pitch is required to drain water away.
Most roof designers refer to a pitched roof as one that is greater than 15°. Less than that and a roof may be referred to as being ‘flat.’
Considerations of roof pitch:
Steep roof pitches are usually considered as those over 45°. This means a greater visual emphasis is placed on the roof and it becomes more of a feature of the property. In the UK and Europe, steep roof pitches are often associated with older traditional style properties, mainly because historically slate and clay tiles were often used since the basic material was more readily available. Clay and slate tend to require a pitch of at least 35° to work effectively.
Steep roof pitches can ensure larger room volumes on upper floors and often become a dominant feature of the design. In such cases, where the roof is very dominant, and if the pitch means tiles cannot be used easily, it is worth considering high-quality long-life materials including standing seam metals like GreenCoat PLX or zinc roofing.
Construction of a Pitched Roof:
There are two popular methods of construction:
Cut Roof: this is constructed on-site using cut timber to make rafters, joists, and purlins.
A Trussed Roof: The word Truss (Image 3 below) is derived from an old French word “trousse” which means a bundle of items. In effect, a Truss is a bundle of timber triangles which form the support for the roofing material. It is often formed off-site and delivered on a lorry.
Image 3: Truss Roof: A roof Truss is a collection of timber triangles that offer design strengths.
There are variations of this trussed roof including:
Image 4: Horizontal steel purlins give roof stability and provide a base to support the roof deck
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