Flat roof as percentage of total roof area

[Bobharford]

Hi
I need to calculate the percentage of my roof that is flat roof for a mortgage application - it has to be no more than 25%. It is a dormer roof projecting out of the tiled roof. So I figured an easy way would be to measure the total roof area and then subtract the dormer roof area.
So: Total roof area 78 sqm
less Dormer roof area 14. sqm
would give less than 25% dormer.
a mate says I need to measure tiled areas only to get tiled roof area and use that for the calculation. Which is a big difference. Does anyone know the method a housing surveyor uses to establish this?
The Building society not helpful as they say they use panel surveyors.
Cheers
Bob

 

[^woody^]

Whether you measure the total area of roof and deduct the flat from the total, or measure the area of pitched (ie tiled) and area of flat separately, the answer is the same.

 

[KenGMac]

Bobharford, good evening.

OK for a mortgage and insurance purposes.

Measure the slope length X elevation width to get the tiled area, it can make a difference on occasion.

The M/G and insurer are looking at the risk posed by the entire surface area of roof and more especially flat roof area

Suggest you do not simply measure the width and depth of the property, but use the above slope lengths.

As a rule, this is a "Tick box Exercise" by the M/G provider.

Flat roofs are viewed as a greater risk than a tiled / slated sloping roof by the M/G provider and insurers.

it is only a very few insurers who ask for Areas of flat roofing in a domestic setting.

Ken