stone coated roofing tiles (decra, armatile, duratile) in overall (roof structure, battens and covering) cost 150% the cost of roofing via concrete or clay tiles i.e. roman tiles, mareba etc

in original analysis the covering will 200% expensive however the sales guys will tell you there will be overall savings in the structure to compensate... this however is not true and at the end of the day you are 50% above...

the situation would change if you threw in the transport cost... if you are building something in Juba... you would need lots of truckloads of the other tiles compared to decra...

@6612..stone coated tiles cost around KES 1,700 per square meter. Clay tiles cost around KES 600 per sq.meter. Stone coated tiles give a 50 year guarantee-the paint is acrylic based and the steel sheet is gauge 26 thick[very thick compared to normal mabati].See this link http://www.metrotile.co.ke/faq.php
Clay tiles are advantageous in that they are made from natural clay and have no added colour in them so you can drink the water without any chance of lead poisoning from the paint.
Clay tiles also become more aesthetically appealing as they age-they turn dark red. They are also light weight compared to concrete tiles . Concrete tiles contain colouring material so the rain water is not safe for consumption.
On the underlay issue, heavy gauge[500] polythene sheeting can be used which is much cheaper-around KES 50 per square meter.This is cheaper compared to gauge 32 mabati which will cost roughly KES 150-200 per square meter. The steeper the roof angle, the less chance for leakages so if your roof is steep enough-over 22.5 degrees, then this polythene underlay is a good choice.

does anyone have experience with Decra? Overall, is it a cheaper option in the long run? is the water safe for drinking?

Where is the best place to buy mabati in Nairobi and it's environs ?
Also, I have been informed that reject mabati are ok if the intention is to have tiles over them. What are Wazuan's thoughts?