Most roofs in the United Kingdom are laid to a pitch well above 20° so there is plenty of choice when it comes to roof tiles. The exception is usually extensions where the builder or architect has not been attentive or where there is limited space for an ideal pitch.
There are many occasions when a standard roof tile just isn’t suitable for the job at hand. This page covers roof tiles for the lowest of pitches, but please remember to double check the official documentation from the manufacturer. They often make changes to their installation procedures to accommodate new regulations
If you are looking for roof tiles designed specifically for low pitch shallow roofs then your choice is very limited. Some concrete based tiles will go down to 15° and a few will even cope well with being laid on a 12.5° pitch. There are even some that will go down to 10°, providing certain very specific conditions are met.
If you decide on a concrete based tile then make sure you choose a smooth finish as opposed to a granular coating. Smoothies are always more suitable for shallow roofs.
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Tiles suitable for pitches as shallow as 15°:
The following roof tiles can be used on roofs with a pitch of no less than 15° :
Marley Mendip – This tile can be laid to a minimum of 15° provided that the headlap is 100mm and you choose a smooth finish tile. Granular coated tiles are only suitable for pitches above 17.5° .
Marley Wessex – This tile is another favourite for those needing a low pitcher, a simple and minimalist tile that can also be laid down to 15° .
These tiles will go down to 12.5°:
Redland Regent – The Redland regent is a bold roll type of tile and can be laid down to 12.5° provided there are no valleys or hips on the roof. This tile can only be laid to this low pitch if the roof is a simple “up and over” design.
Tiles for 10° roofs:
These tiles have been designed for roof pitches as low as 10° , however any lower than this and you will have to consider using a flat roof type coating such as bitumen or Epdm rubber.
Forticrete Centurion – To my knowledge 10° is the absolute lowest you can achieve with a concrete tile and the Forticrete Centurion is the only one tested at this low pitch.
Decra Classic – These are coated, zinc aluminium galvanised steel tile panels with the appearance of traditional concrete roof tiles. They can be fitted to pitches as low as 10° .
Once a tile has been specified for the low pitch roof and the installation instructions have been double checked, make sure you adhere to the following:
- Use a smooth tile if possible, avoid granular finishes
- Never discharge a gutter/rainwater pipe directly onto the roof
- Use fixing clips if specified by the manufacturer, tiles on a shallow roof are more likely to be lifted by wind
- Double check the tile can be used on roofs with valleys and hips at this low pitch. These are the weak spots on any roof, but especially on shallow ones.
How Not to Lay Tiles on a Shallow Roof
I have seen all of these before, some several times:
- Add extra layers of under-felt – this is just wrong! The purpose is the felt is primarily to keep water out should a tile on the roof break. It acts as a temporary barrier until the tile is replaced. It should not be used as a permanent material to keep out rainwater, that is the job of the tiles, not the under-felt. If the felt is subject to prolonged moisture, it will fail. Timbers such as batons will also rot.
- Increase the overlap – this only works down to a certain pitch, after which it is pointless. Refer to the manufacturer’s guidelines here. Best to stay well within the guidelines actually.
- Discharging gutters onto the roof tiles. This a no-no when you have a roof with a very low pitch, you are almost guaranteeing water ingress.
- Sealing the tiles with glues, adhesives and the like. Don’t go there – short term bodge.
- Pay attention to the location of the building. If it is in an exposed location, then wind may drive water under the tile overlap. Roofs located in Scotland are more prone to this.
Roofing contractors should educate themselves on the risks involved with laying tiles on shallow roofs. Water can be pulled up and against force of gravity, not just by wind but by capillary action. This can be avoided by adhering to the strict instructions from the manufacturer, especially if the roof is below 17.5° . Risk of water ingress is greatly increased on roofs with a low pitch and valleys or hips.
Capillary action is not fiction, it is fact and often results in leaky roofs.
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