Roof pitch below spec of tiles - what to do extra?

mark.carline · 31 Mar 2011

We're looking to build a single story extension to the rear of our house and the problem is we really dont want to use a flat roof but the pitch is about 16-17 degrees which is much lower than the 30 degrees that is recommended (and guaranteed) the tiles would work for.

The tiles i would like to use are the Marley Fired Sienna Hawkins Clay ones here:
http://www.marleyeternit.co.uk/Roofing/Clay-Tiles/Hawkins-Clay-Plain-Tile.aspx

I'd still like to use the tiles and we're talking to our builder (who has said to use a different tile which i dont think will look right) and our architect whos looking into it for us.

I wondered what everyones thoughts where here about this ?

Is it just a case of double felting ? or what else could we do ?

Thanks in advance for any advice.

Mark

BethesdaSlate · 31 Mar 2011

Mark

No slates or tiles will 'look right' at 16-17 degrees, as this is well below the minimum pitch at which double lap slates and tiles will work, therefore you wouldn't see it traditionally and would look unnatural in my opinion.

Raise the pitch of the roof if possible, failing this treat it as a flat roof and cover with a flat roof material.

Redland guarantee their Cambrian 'slate-look' tile down to 15 degrees but this will look well out of place if your main roof is clay tile.

Relying on the underlay (even 2 layers) you should only consider this to be a temporary roof as the felt will rot, as will the battens.

SurreyRoofingEstimator · 31 Mar 2011

Use the Onduline undertile system to take the water that will penetrate the tile laps, this will be the weathering layer with the tiles being for show only, the only problem with this (especially at that low pitch) is that frost damage is more likely to occur as water will sit in the laps.

BTW forget Cambrians at this immediate time as you cannot currently buy them (they hope to have them back on the market very soon though) (Marley Melborn is the alternative here)

freddiemercurystwin · 31 Mar 2011

Beware also that, despite any extra measures being taken, Building Control may not accept them, some may argue that BC will not give a hoot (which is true) but I can speak from experience that some BC inspectors will care and will not accept them.

BethesdaSlate · 31 Mar 2011

BTW forget Cambrians at this immediate time as you cannot currently buy them (they hope to have them back on the market very soon though) (Marley Melborn is the alternative here)[/quote]

Just found this out too - although I really don't like them was just about to order some for a job - Marley Melbourne it is then!

hardmetalking · 31 Mar 2011

You could go for a hard metal.........

zinc, copper or stainless steel. Not as expensive as you think and is capable of going down to 3 degrees with a lifetime guarantee.

Worth a thought if nothing else........

blackpoolroofer · 4 Apr 2011

hi I am Dave a roofing contractor from Blackpool the way I have got round this problem in the past is to ply board the roof then felt it as you would a flat roof one layer of good felt is enough torch on felt is easier and quicker then counter batton it for ventilation then proceed to felt batton and tile as normal most building inspectors agree with this as long as you get the ventilation right (usually a good eaves vent system) the is more cost involved but you get the look your after.

if you would like to know more you can find my contact details on http://www.blackpoolroofer.com/

D_Hailsham · 4 Apr 2011

freddymercurystwin said:
Beware also that, despite any extra measures being taken, Building Control may not accept them, some may argue that BC will not give a hoot (which is true) but I can speak from experience that some BC inspectors will care and will not accept them.

The obvious answer is to run the proposed solution pass BC and get their approval in writing. Your architect should do this.

jimAuk · 14 May 2011

Create a pitched from section in a sensible pitch angle, and then onto a queen top, flat roof section.

Maybe put in a large roof lantern on the flat section?

gismo · 21 May 2011

i agree with blackpoolroofer, install a 'hidden flat roof', basically a pitched flat and roof tiled over. a friend of mine is a roofer by trade and has suggested this to me for my build, its widely accepted around my area i believe

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Roof pitch below spec of tiles - what to do extra?

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