Why flat roofs need attention
A flat roof is never completely flat. It relies on a gentle fall to move water towards gutters or outlets. If the fall is poor, water sits on the surface, and standing water puts constant stress on the covering and its joints.
Flat roof coverings generally have a shorter working life than slate or tile pitched roofs, so the age and condition of the covering matter when you are budgeting for a purchase.
Common flat roof problems
These are the issues most often seen on flat roofs over London extensions and dormers.
- Ponding, where rainwater collects instead of draining
- Splits, blisters and cracking in felt or other coverings
- Failed or poorly formed upstands and flashings where the roof meets a wall
- Blocked outlets and gutters, often with debris or vegetation
- Condensation within the roof build-up where ventilation or insulation is inadequate
- Staining or soft areas on the ceiling below
Signs to look for on a viewing
From inside, look at the ceilings under extensions and dormers for staining, bubbling paint or fresh patches of decoration. Outside, see whether you can safely view the roof from an upper window. Puddles long after rain, vegetation growth or patched areas are all worth asking the seller about.
Ask when the roof was last recovered and whether any guarantee or paperwork exists.
How a survey helps
A RICS Level 2 or Level 3 survey will consider visible flat roofs as part of the whole property. Many flat roofs cannot be seen well from the ground or from inside, so the view can be limited.
Where the roof is hard to see, a drone survey can capture close aerial images of the covering, outlets and upstands for a surveyor to review. Where the concern is the structure beneath, a roof survey inspects accessible internal areas and visible timbers.
What it can mean for your purchase
A flat roof nearing the end of its life is not necessarily a reason to walk away, but it is a cost to plan for. Understanding the condition before exchange gives you time to get repair quotes and, where appropriate, discuss the findings with the seller.