Pitched Roof

A pitched roof is a type of roof that slopes downward at an angle, typically in two parts from a central ridge. The angle of the slope, known as the “pitch,” can vary depending on architectural design and functional requirements. Pitched roofs are a common feature in residential and commercial buildings worldwide and offer advantages such as efficient rainwater drainage, aesthetic appeal, and the potential for additional living or storage space in the attic or loft area. They are constructed using various methods, including cut roofs and truss roofs, and come in different styles, such as gable, hip, and mansard roofs.

A pitched roof angles downward, typically in two parts from a central ridge, although sometimes in a single span from one edge to another. The “pitch” of a roof is determined by dividing its vertical rise by its horizontal span, indicating its steepness.

In contrast, a flat roof technically has a slope less than 10°, but in practice, it is often much shallower, typically ranging from 1:40 to 1:80, expressed as a gradient. For further details, refer to Flat roof.

As per the National Calculation Methodology (NCM) modelling guide (for buildings other than dwellings in England) 2013 edition, issued by the Department for Communities and Local Government (DCLG), a pitched roof is defined as having a pitch greater than 20° and less than or equal to 70°; if the pitch exceeds 70°, it must be treated as a wall.

Pitched roofs are constructed using two primary methods:

1. Cut roof: This traditional approach involves cutting timber on-site and assembling the roof using rafters, joists, purlins, ridge boards, etc.
2. Truss roof: Prefabricated trusses are manufactured off-site, then transported to the location and erected. Additionally, there are various other framed constructions available, such as portal-framed roofs.

Types of pitched roofs encompass a variety of styles:

• Mono-pitch roof: A mono-pitch roof slopes from one side of a building (or section) to another. Initially prevalent for Victorian extensions, it remains a popular choice today. In domestic construction, it typically features rafters fixed to walls at each end of the roof span, supporting battens for the roof covering.
• Couple roof: Considered the simplest pitched roof, the couple roof consists of two timber lengths (rafters) leaning against each other, secured at their apex.
• Closed couple roof: To enhance the couple roof’s stability, ceiling joists are added horizontally between the rafter feet. These joists act as ties, preventing outward wall deflection and increasing potential roof span, as well as supporting a flat ceiling if needed.
• Collar roof: By elevating the height of ceiling joists above the rafters’ lower ends, the collar roof allows upper rooms to partly occupy the roof space. This design economises by slightly reducing external wall height and associated brickwork.
• Purlin roof: To extend roof spans without thickening rafters or raising costs, purlins are introduced. These support structures provide additional stability, enabling lighter rafters.
• Large section truss: Trusses offer wider spans compared to traditional methods. In early 20th-century dwellings, two trusses were common, but more could be used based on load requirements.
• Trussed rafter: The prevalent modern trussed rafter, like the fink or ‘W’ truss, incorporates tension and compression members in a W shape. Capable of spans up to 12 metres, it accommodates various pitch angles in contemporary house construction.

What is a pitched roof?

A pitched roof is a type of roof that slopes downward at an angle, typically in two parts from a central ridge.

What are the advantages of a pitched roof?

Pitched roofs offer efficient rainwater drainage, provide additional living or storage space in the attic or loft, and often have an aesthetically pleasing appearance.

What are the different types of pitched roofs?

Common types of pitched roofs include gable, hip, mansard, and shed roofs, each with its own unique design and characteristics.

How is the pitch of a roof measured?

The pitch of a roof is typically measured as the ratio of its vertical rise to its horizontal span, expressed as a fraction or angle.

What materials are commonly used for pitched roofs?

Common materials for pitched roofs include asphalt shingles, metal roofing, clay or concrete tiles, and wood shakes or shingles.

How do I maintain a pitched roof?

Regular maintenance tasks for pitched roofs may include cleaning gutters, inspecting for damage or leaks, and replacing damaged or missing shingles or tiles.

Can I convert my attic space into a usable living space with a pitched roof?

Yes, pitched roofs often provide ample space in the attic or loft area that can be converted into additional living space, bedrooms, or storage areas.

How do I choose the right pitch for my roof?

The pitch of a roof is often determined by factors such as architectural style, local climate, and personal preference. Consulting with a roofing professional can help you choose the best pitch for your specific needs.

Are pitched roofs more expensive than flat roofs?

The cost of a pitched roof can vary depending on factors such as materials, complexity of design, and local labour rates. While pitched roofs may have higher upfront costs compared to flat roofs, they often offer long-term durability and aesthetic benefits.

Do pitched roofs require ventilation?

Yes, proper ventilation is important for pitched roofs to prevent moisture buildup and maintain indoor air quality. This can be achieved through ridge vents, soffit vents, or other ventilation systems.