Low Pitched Roof Guide - Solutions and Considerations

Low-pitched roofs are an ideal choice for those seeking a unique, modern aesthetic to adorn their homes, which also comes with a multitude of benefits.

Designed to be installed at a pitch between 12.5° and 22.5°, low-pitched roofs are becoming an increasingly popular roof choice for domestic extensions or similar builds, thanks to their instant curb appeal and anti-view-blocking properties. It is generally considered that any roof installed at a pitch of less than 10° is deemed a flat roof.

The British Standard for Slating and Tiling BS 5534 (BS 5534) sets guidance and building regulations for roof system projects and historically recommends that any roofing system using slates and tiles is installed at a minimum pitch of 20°. Lower pitches are now possible if required, however, due to new product developments and improvements.

Low-pitched roofs are not only aesthetically appealing, making them a popular choice for architects and creative designers alike, but they also tend to require less material to manufacture and install. These factors have helped make low-pitched roofing a more cost-effective alternative compared to standard roofing.

Typically, a low-pitch roof will sit between 12.5° and 22.5°, with some roofs being pitched as low as 10° when using an overlapping system. However, all low-pitched roof solutions depend on the material used during construction and the roofing tools/building products available.

Important factors to bear in mind when considering a low-pitch roof installation include how effectively rainwater can drain from the roof. If your roof has long rafters, it will naturally have a gentler slope for rainwater to drain from, which can lead to water ingress. For added protection, increase the pitch of the roof by 1° for every half metre distance that a rafter length is over the recommended maximum rafter length.

The most popular low-pitched roofing materials used in extensions include:

• Roofing Felt
• Slate Tiles
• Clay Tiles
• Metal Roofing Sheets
• Concrete Pantiles
• Polypropylene (plastic) Tiles

No matter which material you use for your low-pitch roof, one of the most important things to keep in mind is the use of a roofing membrane. This needs to be installed beneath the roof pitch to weatherproof it against wind-driven rain and snow.

This is because most low-pitched roofs do not have gravity working in their favour when it comes to rainwater runoff and general water drainage. A roofing membrane will prevent any liquid from entering under tiles/sheets through any capillary action.

Low-pitched roofing is commonly used on domestic extensions, bungalows or similar smaller builds.

They are a popular choice for these types of builds because their lower profiles mean that they do not block as much sunlight from the outside space/garden when compared with higher-pitched roofs. They also allow for enhanced views around the building, as well as providing a contemporary aesthetic to the building itself.

Choosing a low-pitch roof comes with a range of benefits when compared to homes with a higher existing roof pitch.

Generally, there are fewer materials required to manufacture the roof itself due to the smaller surface area. This means it requires less manpower and so fewer labour time costs, too.

Another advantage is that low-pitch roofing requires less upkeep than its high-pitch counterparts. If roof tiles or plain tiles are used during installation, there is less gravitational pull due to the lower degree of the roof, and so over time, roof tiles are less likely to fall or become damaged from harsh weather contact.

They are a great alternative to a flat roof, allowing for water drainage and preventing water pooling/ingress, which could potentially damage other parts of your property.

Not all roofing materials are suitable for use on buildings with low roof pitches. Whether a material is suitable depends on its durability, longevity and other performance factors. The most effective and popular roofing materials for a low-pitch roof are as follows:

Roofing felt is a very cost-effective roofing system when it comes to low-pitch roofs. Comprising a breathable base, it is manufactured from natural or synthetic materials and then saturated with a strong protective coating, such as bitumen. Roofing felt can be cut down in size to recreate the overlapping effects of roof tiles or natural slate tiles, or can be laid in larger, longer lengths.

Pros

• Available with a self-adhesive application option
• Anti-freeze properties in cold climates
• Extremely Lightweight and easy to install

Cons

• Potential fire hazard
• Fragile, can tear easily
• Susceptible to puddling in the rain if not fitted correctly

Slate roof tiles are favoured by many for their durability and unique kerb-side appeal, and are a highly sought-after choice for both high and low-pitch roofs. When it comes to roof slates on a low-pitch roof, the best method is to use the single-lapping method, as it results in a more flush, flatter surface. Single lapping also has better water drainage properties when compared with double lap tiling.

Pros

• 100% natural and attractive material
• Good longevity with a lifespan of up to 100 years
• Environmentally friendly
• Great fireproof properties when compared with other roof tile materials

Cons

• Slate tiles are one of the most expensive roof materials
• Natural slate is a heavy material, and so supportive weight-bearing battens are required on your property in order to keep your roof risk-free
• Roofing slates can be fragile and need to be handled and installed with care.
• Lower-grade slates can also contain pyrites, which, over time, can rust and stain your roof

Clay tiles are a traditional roof material that has been in use for thousands of years. Known for their consistent profile, colour and size, plain tiles can be installed down to a pitch as low as 35°. However, for low-pitch roofs, tiles can be manufactured as "interlocking tiles" and can be installed at a minimum pitch of 15°, making interlocking tiles best suited for low-pitch roofing.

Pros

• Aesthetically appealing
• Colour consistency for uniformity
• Can endure harsh weather conditions

Cons

• Tiles are heavy, putting more stress on the roof structure
• They can take longer to fix in place due to their fragile composition, leading to higher labour costs
• More expensive than other roof tiles

Metal roofing sheets are a high-quality, low-maintenance option for low-pitch roofs, available in a wide range of profiles, colours and coatings. Depending on the profile you choose, they can be installed at pitches as low as 4° for box profile, 6° for standing seam, 10° for corrugated, and 12° for tile form, making them an excellent choice for creating a low-pitched roof.

Pros

• Low-upkeep
• Strong and durable, with a lifespan of 40+ years when coated
• 1m cover width when lapped
• Can be cut to custom lengths

Cons

• Sheets can be dented by a heavy downward impact
• They can be noisy in heavy rain
• Best suited to agricultural and commercial builds as opposed to domestic extensions

Another benefit of metal roofing sheets is that they're available in various designs. As well as modern standing seam, which creates a contemporary aesthetic, there are also tile effect sheets, which bring the timeless charm of traditional clay tiles, but with all the benefits of metal sheeting.

They can also be fitted on low roof pitches (recommended minimum pitch of 12°) and can be cut to specific lengths to accommodate any roof size. As well as domestic extensions, tile effect sheets are suitable for agricultural, domestic and commercial builds.

Concrete tiles have been used as an alternative to traditional roof materials, such as clay tiles, for over a hundred years and typically work at a minimum pitch of 15° when used as a low-pitch rooftop solution.

Pros

• No need for protective treatments
• Environmentally friendly materials

Cons

• Heavy and can be difficult to install
• Easily breakable
• Poor weather resistance and do not age nicely

The cost of concrete roof materials comes in at around 20% cheaper than its clay counterpart, making it an economic choice in comparison.

Concrete tiles are best suited to homes that want to replicate the look of a traditional tiled roof without the cost.They are also hard-wearing, with a lifespan of around 35-50 years.

Plastic roof materials are one of the cheapest low-pitch roof coverings on the market. Due to their polymer composition, they typically have a long life span. However, it is not known at the moment just how long they will last, as they are still a reasonably modern building material.

Pros

• Available in a variety of colours
• Low-cost
• Lightweight and easy-to-install

Cons

• Low-insulation properties
• Unknown longevity, as they are a relatively new material that isn't as strong
• Not an environmentally friendly material

If you choose a low-pitch roof, there are several potential financial benefits. Because low-pitch roofs cover a smaller area compared to a typical pitched roof, they require fewer roofing materials and accessories, saving you money on supplies and labour costs.

Metal roof sheets, tiles, and natural slates make for very low-maintenance, low-pitch roofs. With tiles and slates, individual tiles may become damaged but can be easily replaced without affecting the other surrounding roof tiles.

To minimise any risk of problems developing on a low-pitch roof, it is important to use a professional building contractor to fit it.

In the UK, a standard roof pitch typically ranges between 30° and 50°. This range provides good protection from the famously unpredictable British weather (wind, rain and hailstorms) as well as having effective thermal properties and water runoff.

With additions to buildings, such as domestic extensions, however, steeper roof options aren't always possible. For this reason, lower-angle roof pitches are often used instead.

Due to the nature of their low profile, these types of roofs can be more susceptible to leaks as they allow for less water runoff than their high-profile counterparts. This can lead to additional maintenance and potential repeat repairs.