What Are The Most Cost Effective Roofing Materials?
This is not a straightforward question as the answer depends on your definition of what you view as 'cost effective'.
This question should perhaps be asked as below:
What Roofing Materials Are The Cheapest To Buy And Lay?
Concrete interlocking roof tiles are the cheapest way to cover your roof assuming that you are looking at the purchase cost of the tiles per square metre, not forgetting the 'hidden costs' of the roofing batten and the nails.
In terms of square-metres-covered-per-pound, then either the 15 x 9 concrete interlocking roof tiles (such as the Redland 49, Sandtoft Standard Pattern and Marley Ludlow Plus) or the large format interlocking roof tiles (such as the Redland Double Roman, Sandtoft Double Roman, Sandtoft Double Pantile amongst others) are always going to the cheapest option.
What Roofing Materials Are The Most Cost Effective Overall?
From this perspective - where we now include the useful lifespan of the roof tiles in our thinking - clay machine made plain tiles are the most cost effective roof covering.
Although slightly more expensive per square metre to initially purchase (including the 'hidden costs' of batten and fixings), clay roof tiles will last at least double, if not three or four times as long over time as concrete roof tiles, so if looked at from the perspective of cost-per-square-metre-per-year, then clay machine made plain roof tiles win hands down.
Clay roof tiles also have an aesthetic advantage over concrete roof tiles, and are looked at as a postive feature that adds value to a property by many people so they should, perhaps, be viewed as not only a more economical long term option, but also one that may well yield a return on the original investment in terms of a higher selling price achieved for the property when it is sold.