What Happens During a Flat Roof Survey?

A good flat roof survey looks well beyond the surface. Here is what gets checked, how to prepare, and how to read the findings before deciding on repair or replacement.

A flat roof survey checks the condition of the covering, the joints and edges, how well the roof drains, the state of the deck underneath and whether moisture inside is a leak or condensation. The aim is to tell you whether the roof can be repaired, how long it is likely to keep going, or whether replacement is the better use of money.

It is most useful before buying a property, when a leak keeps coming back, or when you are weighing a repair quote against replacement.

On the roof: the covering itself

The surveyor identifies the system first, because felt, EPDM rubber, GRP fibreglass and lead each fail in their own way. Felt is checked for blisters, cracking, lifting laps and bare patches where the mineral finish has gone. Rubber is checked at seams, corners and trims. Fibreglass is checked for hairline cracks, particularly at board joints and around upstands.

Soft spots are noted by careful pressure underfoot or by hand, since sponginess usually means wet or decayed boards below the surface.

Standing water after dry weather is one of the clearest signs a flat roof is struggling. The survey looks at where water collects, whether the fall leads to the gutter or outlet, and whether outlets are blocked, undersized or badly sealed. Persistent ponding speeds up wear on every type of covering and puts load on the deck.

Edges, upstands and junctions

Most flat roof leaks start at the edges, not in the middle. Upstands against walls, flashings into brickwork, trims at the drip edge, and details around rooflights, lanterns, vents and soil pipes are all examined. Cracked flashing, open pointing above an upstand or a trim that has pulled away can let water behind an otherwise sound covering.

Inside: the underside and the air

Where the ceiling or deck can be seen from below, the surveyor looks for staining, mould, damp timber and sagging. The pattern matters. A single stain near a wall points to a junction leak. Widespread damp spots, especially in winter, can be condensation from warm air meeting a cold deck, which new covering alone will not cure. Our guide to damp patches on ceilings explains how to tell the two apart.

Note when leaks happen: during heavy rain, only in wind from one direction, or on cold mornings. Take photographs of any stains, and find any paperwork showing when the roof was laid or last repaired. Clear access to the room below, and to a loft or void if there is one. None of this needs anyone to go onto the roof.

You should come away knowing what the roof is made of, what is wrong with it, what is causing the problem and what the realistic options are. A useful survey separates urgent defects from items that can wait, and is honest when a repair will only buy a short time. With us, that is followed by a written quote for whichever option you want to take forward.

How long does a flat roof survey take?

It depends on the size and access, but most domestic flat roofs such as extensions, garages and dormers are looked at in a single visit.

Can a survey tell whether my ceiling damp is a leak?

Often, yes. The location, timing and pattern of the damp, together with the state of the covering, usually show whether it is a leak or condensation.

Is it worth surveying a flat roof before buying a house?

Yes. A general building survey may only note a flat roof in passing, while a roofer can say how it was built and what it is likely to need.

It helps, so you can describe when leaks appear and give access to the room or void underneath, but the roof itself is inspected from outside.

Will the survey recommend replacing the whole roof?

Only where that is genuinely the better option. Many flat roofs can be repaired, and the survey should say plainly which one yours is.

Not sure what your flat roof needs?

Book a visit and we will tell you plainly what we find, what is causing it and whether repair or replacement makes more sense.

Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.