Recommended slope for slated roof

Postby Edpaterson » Mon Feb 16, 2009 11:45 am


I have a lean-to utility room adjacent to my kitchen. The roof is composed of wooden sarking fixed to 5X2 inch rafters covered with mineral felt then slated. I am a little concerned that it is not shedding water properly. Is there a minimum angle for slated roofs? If I have to remove slates would aluminium corrugated sheeting be an adequate substitute?

Ed Paterson
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Simply Build It

Postby stoneyboy » Mon Feb 16, 2009 7:07 pm

If you are referring to flat slates then they can be used down to about 20 degrees provided a headlap of at least 115mm is used. The headlap is the amount that a tile overlaps not the tile underneath it but the top of the one under that.
The major problem with metal sheeting is condensation - something you would have to design for if you use aluminium.
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Postby Perry525 » Mon Feb 16, 2009 8:35 pm

You would imagine that the other parts of the property would give you a clue. After all they are possibly working OK?
However, a slope that works on one property in one area may not work on a more exposed property where it is close to the sea or high up and subject to strong wind driven rain.
The rule of thumb is the more expensive the property the steeper the roof.
In the USA they have discovered that post Katrina buildings erected under the new rules have all survived very and no one has been killed, now the problem is wind driven rain, they have not solved the problem of keeping them dry.
Have a word with your local council.
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