That sounds simple. It is not, because the honest answer depends on the shape of your roof, and almost nobody explains that before quoting. People start ringing builders having decided they want a dormer, and end up comparing three quotes for three different jobs without realising it. We are a matching service. We are not builders. We do not employ surveyors, structural engineers or roofers, we do not carry out the work, and we do not manage your project.