There are mainly two ways of doing the roof. The first is to have a ready made truss roof which is made for you and brought to the site and connected within a week and the second is a cut roof, which is timber delivered to the site and cut and connected by your roofer.
As far as the cost, truss roof’s cost fractionally cheaper as there is less labour work. The trusses themselves cost more than the loose timber but the whole roof would go up a lot faster.
Depending on the design and the shape of the roof, you can decide which method to go for to suit you. If you decide to go for a truss roof, they need to be spaced 24 inches apart and if you go for a cut roof, then it should be 16 inches apart. On average the cost of a truss for our example would be around €70 each and you can calculate how many you need by dividing the length of the house by 0.6 of a meter. So in our example, if the length is 16 meters we then have 16/0.6=26.66 or 27 trusses. 27 trusses at €70 equals to €1890.
You then need other timber to connect the trusses together and also some wall plate which really is a 4x3 timber that sits on top of the blocks and is nailed into the wall by braces. You should include another €1000 for these other extra’s.
On top of the truss, you have to place some sort of felt or membrane and they usually cost around €30 to €40 per roll of 20 meters by 1.
After the membrane has been placed you need to batten the roof, which is usually done by placing 2x1 timber horizontally and place the tiles on the top of them. The cost for tiles are approximately €1050 per thousand and if you wish to go for slate, the cost starts at approximately €1350 per 1000.
After the tiles/slates have been placed, you need to put ridge tiles on the top and they cost approximately €4 to €9 each.
To finish the roof, you need soffit and fascia and the guttering and you should allow another €2000 to €3000 for them.
Do remember that on top of all the above you have the cost of the labour or the contractor.