Pitch perfect

As demand for low pitch roofing products continues to grow, Stuart Nicholson, Roof Systems Director at Marley, helps merchants answer common customer queries.

Since the relaxation in planning laws for single story rear extensions back in 2014, demand for low pitch roofing products has increased significantly. This is because this type of project often calls for a lower pitched roof due to the position of first floor windows and to maximise floor space, yet homeowners tend to prefer the performance and aesthetic of a tiled roof, rather than a flat roof.  

Whereas in the past, there was a very restricted range of products for low pitch roofing projects, now customers no longer have to compromise on style, texture or colour. In fact, there is a growing selection of tiles specifically designed for low pitch roofs and recent innovations mean there are some great, easy-to-install clay and concrete options.

Here, we answer some of the most frequent questions that you and your customers may have about low pitch roofing products:

1. What counts as a low pitch roof?

The pitch of a roof is governed by a number of factors, such as the foundation footprint and building height limitations. Typically the average roof pitch for new build properties in the UK is circa 30-35 degrees, although this may vary for a number of design reasons. Traditional concrete interlocking tiles are designed to perform down to 22.5 degrees, anything lower than this, particularly less than 15 degrees, is considered as low pitch. If a roof pitch is below 10 degrees, you would either need a conventional flat roof solution or consider large format cement or metal corrugated sheets instead, which can typically fall into the flat roof category.

2. Can I get any concrete tiles that can be used below 15 degrees?

The newest low pitch concrete interlocking tile in our range, Mendip 12.5, which has been designed with low pitch projects in mind. It has the same double pan design as the original Mendip tile, but has special weatherproofing channels so that it can be used down to a very low pitch of 12.5 degrees. It is already available in two colours, Smooth Grey and Smooth Brown, and we are about to launch a new colour, Old English Dark Red. 

We also offer three other low pitch concrete roof tiles. Our large format Wessex and Mendip concrete interlocking tiles can be used down to a minimum 15 degrees pitch and our thin leading edge, slate effect Edgemere interlocking tile has a 17.5 degree minimum pitch.

3. What is the lowest minimum pitch for a clay roof?

When it comes to clay plain tiles, we are the only manufacturer who offer two types of single camber tile which can be used on roof pitches as low as 30 degrees, whereas the majority of single and double camber clay plain tiles can only be used down to 35 degree pitches.

However, there are also clay interlocking tiles which allow customers to achieve the traditional clay look at a much lower pitch. For example, our Melodie clay interlocking pantiles can be used on pitches as low as 12.5 degrees.

For a more rustic appearance, our Lincoln interlocking pantile has a low minimum pitch of 17.5 degrees.

4. Are there any slate options for low pitch roofs?

BS 5534 recommends that the minimum pitch for natural slate is 20 degrees, but there are some very good slate effect tiles that can replicate the slate look at a lower pitch for extension work. For example, our Edgemere range of thin-leading edge concrete slates give a slate look but are more cost effective and can be used down to pitches of 17.5 degrees. They come in a variety of colours and textures, including Riven, to help your customers match the slate aesthetic they need.  

5. What happens if a customer wants to use a product below the recommended minimum pitch?

You should warn against this as laying a product below its minimum pitch can prove to be a costly mistake. As well as the risk of invalidating warranties, the roof might not be signed off by building control upon completion, so it is always important to check with the manufacturer.
If roof tiles are installed below the recommended minimum pitch for aesthetic reasons, then the tiles should not be relied upon for performance. However, there may be proprietary sub-roof systems on the market to install beneath the tiles to provide this necessary function. In these instances, checking exposure is very important because the higher the rainfall, then the riskier this approach is. Our advice follows the BS 5534 recommendation that ‘a roof designed below the recommended roof pitch should have a functional weatherproof sub-roof system to remove any rainwater ingress safely to the eaves gutter’.

6. Are there additional products that should be purchased?

All of our low pitch roof tiles are also available to purchase as part of a full roof system with battens, underlay, ventilation and fixings, backed up by a free 15-year guarantee.  Extensions still need to be fixed in line with BS 5534 and purchasing a full roof system will help customers to make sure their project is fully weather tight and compliant.