How should I prepare a new roof installation?
Start early and find a local roofing specialist, to get a project estimate. This way, you can plan your budget, make savings or identify other financial options.
Also, you should determine which part of the building will be affected by the installation of the roof, so you can isolate it if possible. People will not be productive if they are forced to work while roofers hammer up and do the other operations specific to their work. Also, ensure that the area around the building is clean, and the driveway – free, so that roofers have enough space to install the safety equipment, bring the materials and dispose debris.
The existent roof must be removed, or can I opt for adding the new coat over the existing one?
That depends on a lot of factors: the type of the roof, the existing materials, their condition etc.
In the case of a flat roof, EPDM membrane systems can be overlaid on existing coverings by a licensed EPDM roofer, but the surface requires special preparation and it is often easier to strip the roof of the material. In the case of a sloped roof, very few materials can be installed over an existing roof, because of the extra load they put on the structure. Also, the old roof will be stripped down if it is unstable and saturated.