Building a Cross Gabled Roof
A cross gabled roof is very sound and handles rain and wind very well.
A cross gabled roof is not something that should be designed by an amateur. The roof is a change to the structure of your property and needs to be of a standard that your insurance company will cover against normal risks.
An architect will be able to check the original building design and make sure that your alteration will not affect the efficiency of your roof. He will also be able to check to make sure you are complying with local planning regulations.
You need to visit several contractors to get tenders for the work. Your architect would be able to say what materials are needed and you could either buy them independently or let the contractor buy them. You should also check that your home policy covers the contractor against injury and so on.
Do It Yourself?
If you are a very accomplished D.I.Y. fan you could possibly do the building yourself but you could have problems getting your home coverage to include your work. If anything goes wrong with the roof, a contractor will have a guarantee but you will not be able to give yourself a guarantee.
While building a cross gabled roof is a relatively simple exercise this is one thing a gifted D.I.Y. fan should leave to the professionals.