How do I get round this one - roof pitch with plain tiles...

[larrylamb11]

Building an extension with a lean-to porch in a conservation area..... all the rest of the house and the extension is built and tiled with Redland Heathland concrete plain tiles or traditional clay tiles. We have come to rough out the dimensions for the porch as the next stage to discover that the roof pitch has been designed at 22deg....... The specs for Redland Heathland are for minimum pitch 35deg.
Why on earth the architect designed it like this we have no idea - clearly he has cocked up again.
Having gone back to the drawing board we reckon we can increase the pitch to 30deg but not much more (door head and 1st floor window cill restraints).....
How low a pitch can I get away with on a plain tile roof and what is the best way of preventing any potential leaks?
Having rung the architect to get his ideas, he said "easy solution, roof it in slate".... which I really don't want to do as it won't match anything else on the house or in the area..... he has clearly missed the point of what we are trying to achieve...... yes, I am pretty chuffing cross about it!
He reckons it will probably be alright done at 30deg and in concrete plain tiles and suggests we give it a go at that. I don't trust what he is saying and feel he is in damage limitation mode having screwed up. I now have to try and come up with a solution to get this roof on and watertight - anyone got any ideas?

 

[freddiemercurystwin]

First things first, apart from your own obvious trepidations, you may need to be very careful on the choice of roofing materials if you're in a Conservation Area. Unless you're matching the existing you often have to get different roofing materials approved by the Conservation Officer/Planners before you can fit them.

Is he suggesting you use the tiles anyway? Building Control may not allow their use as they are outside of the manufacturers tolerances and the manufacturers warranty will be ineffective too. Having said that, unless you're on the top of a mountain or right on the coast they'll probably be ok.

There are various alternatives available though such as these http://www.marleyeternit.co.uk/Roofing/Concrete-Tiles/Ashmore-Interlocking-Double-Plain-Tile.aspx , I'm sure the roofers will be along to offer a few more alternatives, its just a case of trawling the web to find a few and then get samples of them to establish the best one and as mentioned if needs be get approved by Planning.

Realistically though your Architect should be doing all this. If he gets snotty and you feel like getting snotty yourself you could consider reporting him to the RIBA telling him you're getting a solicitor involved and tell him that your solicitor has suggested the Architect informs his Public Indemnity Insurance Supplier that a claim may be headed his way. That will probably see his underwear change to a dark shade of brown.

 

[garyo]

I'm in a similar situation, and am going to use the Marley Ashmores as a solution. The other popular one is the Santoft 20/20 :

http://www.sandtoft.com/tiles/our-products/natural-clay-range/new-generation/2020/product/

Both are rated down to ~20 degrees.

 

[datarebal]

You'll probably get away with 30 degrees if you close the gauge down.

 

[larrylamb11]

Thanks for those suggestions, good to know there is a proper solution. With your ideas and after consulting the builder and architect again, it looks like we are going to close down the guage and use the Redland plain tiles at 30deg.... swapping to the interlocking tiles if this fails to be waterproof. The builder is pretty confident it will work and it keeps all the roof coverings consistent which is important.
This is for a north-west facing porch in the Thames Valley, so hardly prone to extreme weather. Fingers crossed we get away with it

 

[datarebal]

it will work.