Technical Tips
When it comes to roofing, some of the most frequent online searches we see are about installing tiles at low pitches and the minimum pitches for different roof tiles or slates.
This corresponds with the continued growth in demand for low pitch roof solutions over the past few years, which is being driven by the trend for large commercial roofscapes. Many homeowners today prefer the aesthetic of a pitched roof over a flat one for a rear extension but need tiles that will match the main roof. Inevitably these need to perform at a lower pitch because of the position of first floor windows.
Traditionally contractors would have installed pitched roofs at 20° but it's becoming increasingly likely that they will have to work on some low pitch roofing projects.
Below we've addressed some frequent technical queries about creating low pitch clay roofs:
What is the lowest pitch for a clay roof?
Our Snowdon & Shetland interlocking clay tiles allow you to achieve a traditional clay look at a much lower pitch such as 12.5°. These clay tiles are particularly good for extension projects where the roof may be lower than the main property but needs to blend with original pantiles.
Why can our clay tiles be used as a lower pitch?
The weathertightness of roof tiles and slates decreases as the roof pitch gets lower and rafter length increases becauase it takes longer for water to drain from the roof. The reason our tiles can achieve such a low minimum pitch is because we put them through rigorous and extreme testing processed which go above and beyond what a normal roof tile would be exposed to. They also incorporate special features which allow them to be installed at a lower pitch.
What happens if I need to go below the recommended minimum pitch?
It's important to remember that local building surveyors will almost always check the roof tiles are suitable for your pitch. Laying a product below it's minimum pitch can prove to be costly mistake so please check suitability.
If you do decide to install roof tiles below recommended minimum pitch for aesthetic reasons then the tiles should not be relied upon for performance. There may however be proprietary sub-roof systems on the market by others to install beneath the tiles to provide this necessary function. In these instances checking exposure is really important because of the higher rainfall, then the riskier the approach is. Our advice follows 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 rain gutter.'
What other tips do you have for installing low pitch roofs?
- Give careful consideration to how the whole roof system will perform at a low pitch ad check compatibility. All of our low pitch options have matching fittings for ease of installation and additional protection.
- A low pitch roof on an extension may have to deal with an increased amount of water coming from a larger roof above so it needs to be designed carefully, with consideration given to where the water run off will be.
- On adjacent roof slopes of varying pitch, set batten gauge to the lower roof pitch to ensure alignment at intersections.
- Another area to watch out for with low pitch roofs is ventilation. Normal contour vents can usually only be used down to a pitch of 20° so tile vents are not always suitable for low pitch installation. Instead a dry fixed eaves vent system can be used.