thanks for all your replies i do appreciate it!
i am not trying to step on anyones toes.. i just wanted to no if there was a general calculation.
I would be getting work for roofing companies and all i am trying to do is get them involved in the intial quote... i presume it would just be...
WE are an Interior design consultancy, we are looking to branch out into loft and dorma conversions.
Although we have contracted joiners/p&d's/plasterers/electricians and plumbers, we are finding that alot of customers are wanting re roofs or re linings @ the point of creating the new...