Size – obviously the greater the roof area the more materials, labour and scaffold will be required.
Then there is the design of your roof, the greater the complexity, the higher the cost. This is simply due to the fact that complexity means your roofer will take longer to install the roof and require a higher proportion of specialist fittings. Elements that add complexity include dormers, roof lights, valleys and hips. The cheapest roof design is a simple duo pitch (up and over) with nothing breaking up the roof slope.
Where you are located and what’s around your property; the height of the building, the position or proximity of adjacent properties and local topography can all impact on cost. More exposed locations will require a greater amount of fixings to individual tiles and slate, which increases labour and material costs. What’s around your building can have an influence on the cost of erecting the necessary scaffold and gaining access for materials to be delivered – all of which must to be done in accordance with health and safety regulations.
When your old roof covering is removed there are additional factors that come into play. In cases where torching or spray foam insulation has been used on the back of the original tiles, the cost of stripping them off can increase significantly. Alternatively, you may find that a proportion of your tiles or slates can be reused on the new roof, or sold to a reclaimed merchant, which will reduce the overall cost. Finding value in your roof like this only usually applies to clay tiles and natural slates due to their durability and colour-fast nature.
The elements that surround your roof such as facias, soffits, bargeboards and gutters can all add to the cost if they need replacing or repairing. For items that are near the end of their life it might be tempting to put off dealing with them now, and try to eek out a few more years of use. However, be aware that while the scaffolding is up, it is far more cost effective to do the work at the same time as the roof covering instead of having to return in a couple of years, or whenever these elements fail.