15 degree roof design

[jimbob999]

I'm brand new to all this and have been searching online for weeks for the answer, so would appreciate any advice, suggestions or links.

We are in the process of pricing up for an extension that our architect has designed which involves a 15 degree pitched roof to the rear.
This runs across the back and is 13m in total (so the two pitched sections are 6.5 m each).

I've been looking at the marley Melbourn slates, the sandtoft 20/20 and more recently a plastic slate by tapco slate.

Since looking at the melbourn the price seems to have gone up from £2.27 to £2.49 and the tapco slates some people have siad they have got them for 40p but I can't find for less than £1.99 (on internet).
THe Tapco design relies on laying on 18mm board, and use 22 slates per m2, are there any issues related with this (other than being really expensive)?
The sandtoft appears to be cheapest, but is quite heavy and thick tiles.

We're after a flat type slate/tile which rules out a lot of alternatives. Don't want ridges in the tile.
So far the melbourn is favourite but due to reroofing whole house its about £3000 more than 20/20.

ANY ALTERNATIVES/SUGGESTIONS TO THE ABOVE?
Or anyone know any good sources, merchants/online etc

 

[Roofer]

The Redland Cambrian slate is similar to the Melbourn and IMO is a better looking product.

Regardless of what Tapco say I wouldn't be confident about putting the slate on a 15 degree roof, and I can't see what difference it would make if it was boarded.

The Sandtoft 20/20 is a good product but it doesn't look like slate. The weight of them is not an issue; your roof will be built strong enough to support them

 

[freddiemercurystwin]

You could lower it a little and do it in metal, zinc standing seam looks nice, if you like the look. Your architect needs to ensure that what he designs will be approved by Building Control, boarding beneath is a recognised method of getting to lower pitches than the manufacturers recommended minimum but not all inspectors will accept it. but tile that is designed to cope for 15 will work if it is installed correctly.

You know the 20/20 comes in a grey right?

 

[hardmetalking]

Freddy - the money is in the post

 

[freddiemercurystwin]