My Flat Roof Is Leaking – Has the Roof Failed?

What to check before assuming your flat roof installation has failed

Water appearing inside a building can be alarming. Whether it is a small damp patch, staining to a ceiling or significant water ingress, the first thought is often the same:

“The flat roof is leaking.”

And sometimes, the roofing system is the cause.

However, water ingress does not automatically mean that the roof itself has failed.

At Enviroply Roofing, we regularly hear from customers who have previously had a new roof installed or an existing roof refurbished and, when water starts entering the building, understandably come straight back to their roofing contractor.

In some cases, investigation identifies a genuine defect or roofing issue.

In others, the roof installation remains sound and the cause is related to something that has happened to the roof since installation.

Blocked rainwater outlets, lack of maintenance, debris, contamination, subsequent works by other contractors, accidental damage and unauthorised repairs can all contribute to problems with a flat roof.

So, before assuming that your flat roof has failed, it is important to establish what has actually happened to it since it was installed.

A new flat roof is not a maintenance-free roof

A professionally installed flat roof is designed to provide long-term protection, but no roofing system should simply be installed and forgotten.

Throughout its life, a roof is exposed to:

rain and standing water
wind and severe weather
leaves and organic debris
dirt and environmental contamination
moss and vegetation
birds and other wildlife
foot traffic
maintenance activities
plant and equipment
other contractors accessing the roof
accidental damage

Regular roof inspection and maintenance help identify problems before they develop into significant water ingress or expensive repairs.

This is particularly important for commercial, industrial, education, healthcare and other buildings where roofs may be accessed regularly by maintenance teams and different contractors.

A roof that is maintained is very different from a roof that is simply left alone.

Industry guidance for flat roofs with continuously supported flexible waterproof coverings is set out in BS 6229 (and the NFRC’s flat roofing guidance). In practical terms, that includes planned inspection and keeping drainage clear so the system can perform as designed.

Is a blocked roof outlet causing the problem?

One of the first things worth considering when investigating water ingress is drainage.

Flat roofs are designed with falls to direct rainwater towards suitable drainage points. If outlets, gutters or other drainage routes become blocked, water cannot leave the roof as intended. See our guides on how drainage works on a flat roof and drainage options for flat roofs.

Leaves, dirt, vegetation and other debris can collect around outlets over time.

During heavy rainfall, a drainage problem can become particularly noticeable as water begins to accumulate on the roof — which can also lead to ponding.

Ask yourself:

When were the roof outlets last inspected and cleaned?

If you cannot remember, or there is no record of regular maintenance, drainage should be one of the first things considered.

A blocked outlet does not necessarily mean the roofing membrane has failed.

Could a lack of roof maintenance be responsible?

Regular maintenance is an important part of protecting a roofing system throughout its service life.

Maintenance can include inspection and cleaning of:

rainwater outlets
gutters and drainage channels
roof surfaces
perimeter details
flashings and upstands
seams and joints
roof penetrations
areas around plant and equipment

It can also identify physical damage, deterioration, contamination and other issues that may otherwise go unnoticed.

Without regular inspection, a relatively minor problem can remain undetected until water eventually finds its way into the building.

Prevention is almost always preferable to waiting for water ingress before investigating the condition of the roof. A maintenance contract can put cleaning, visual checks and planned inspections on a fixed schedule.

Could poor maintenance affect your roof guarantee?

This is an important point that is sometimes overlooked.

A roofing guarantee is not necessarily the same as a promise that every problem affecting a roof throughout its life will automatically be covered.

Manufacturer and system guarantees have specific terms and conditions. Depending on the roofing system and guarantee, these may include requirements relating to inspection, maintenance, access, protection and the way subsequent works are carried out.

Failure to comply with applicable maintenance requirements can affect the validity of a roofing guarantee. Many membrane guarantees expect regular professional maintenance — typically including clearing rainwater outlets and inspecting for damage — often recommended twice a year (spring and autumn), after severe weather, and after other trades have worked on the roof.

For this reason, building owners and facilities teams should keep appropriate records of inspections, maintenance and any works carried out on the roof.

It is also important to understand the specific conditions attached to your particular roofing system and guarantee rather than assuming that all roof problems will be covered.

If you have a roofing guarantee, check its requirements and keep the relevant documentation. Enviroply installs manufacturer-backed systems from partners including Sika Sarnafil, IKO Armourplan, Protan, Alumasc and Bauder — each with its own guarantee terms.

Has another contractor been on the roof?

This is one of the most important questions to ask when investigating a roof leak.

A roofing contractor may complete a new roof or refurbishment to the required specification, only for other contractors to access the roof afterwards.

This could happen during:

air conditioning installation or maintenance
electrical works
solar PV installation
ventilation works
plant maintenance
rooflight works
building maintenance
refurbishment
mechanical services works
other construction activities

Every additional contractor who accesses a completed roof introduces another opportunity for accidental damage if the correct precautions are not followed.

A membrane can be punctured, cut or damaged by tools, equipment, fixings or materials. Damage may also occur around penetrations, details or access routes.

And importantly, the damage is not always obvious.

A roof can appear perfectly normal from ground level while damage is present elsewhere.

“We didn’t damage the roof” – but could something have happened?

Roof damage does not always look like a large hole or obvious tear.

Small punctures, cuts or damage around details can be difficult to identify without a proper inspection.

Damage may also occur through:

unsuitable footwear
tools or equipment being placed on the membrane
materials being dragged across the roof
fixings or debris
unprotected access
plant or equipment
repeated foot traffic
subsequent construction works

This is why suitable access routes and protection are so important.

Where other contractors require access to a completed roof, they should understand the roofing system and follow the appropriate precautions.

Where other contractors require access to a completed roof, building owners and facilities teams should consider keeping a roof access register. This can provide a record of who has accessed the roof, when they accessed it, why access was required and what work was carried out.

It can also be useful to operate a roof access permit or authorisation process, so that access is formally approved before anyone goes onto the roof and the appropriate precautions can be confirmed.

The original roofing contractor cannot control what happens to a roof after completion unless suitable arrangements are in place.

Could something have been put onto the roof?

Another issue we sometimes encounter is contamination or attempted repairs using products that were not part of the original roofing system.

When water appears, it is understandable that someone may try to stop it quickly.

A property owner, maintenance team or another contractor may apply a product that appears suitable for sealing the area, such as:

mastic or sealant
bituminous products
adhesive
tape
coatings
other waterproofing products

The problem is that not every product is compatible with every roofing system.

A product that appears to solve a leak temporarily can potentially create another problem, interfere with the existing roofing system or make the original source of water ingress more difficult to identify.

Compatibility depends on the particular roofing membrane, system and product, so it is important not to assume that a product suitable for one type of roof is suitable for another — whether that is single ply, liquid waterproofing, hot melt or bituminous felt.

A well-intentioned repair can sometimes create a bigger problem.

If a roof is under guarantee, unauthorised alterations or repairs may also have implications under the relevant guarantee terms.

If you have water ingress, it is generally better to establish the cause before applying a product to the roof.

What about contamination?

Contamination is not limited to leaves and natural debris.

Roofs can become contaminated through their surrounding environment or through activities carried out on or around the building.

This can include:

dirt and dust
organic matter
moss and vegetation
bird contamination
construction debris
chemicals
oils or other substances
products applied during subsequent works
materials from other roofing or building activities

Some contamination may simply affect the appearance of the roof.

Other contamination can interfere with drainage, affect components of the roofing system or make inspection and maintenance more difficult.

This is another reason why regular professional inspection is valuable.

Water inside the building does not always show where the leak started

Another common misconception is that the point where water appears inside the building must be directly below the source of the leak.

It may not be.

Water can travel through a roof build-up before becoming visible internally.

It can move along or through components of the construction and emerge some distance from where it originally entered.

This means that a damp patch or water stain on an internal ceiling does not necessarily identify the exact location of the roof defect.

Finding the source of water ingress can therefore require more than simply looking directly above the affected area.

A proper roof inspection should consider the wider roof area, drainage, details, penetrations and any changes or works that have taken place since installation. A commercial roof survey is designed to do exactly that.

Has the roof experienced severe weather?

High winds, storms, prolonged rainfall and other severe weather can place additional demands on a roofing system.

Following significant weather, it is sensible to check for:

displaced or damaged components
damage around perimeter details
debris
blocked drainage
damage caused by external objects
damage to rooflights or other penetrations
signs of water ingress

If damage is suspected, early investigation can help prevent a relatively small issue from becoming a much larger problem.

Before assuming your flat roof has failed, ask these questions

If you have discovered water ingress, consider:

Has the roof been regularly maintained?
Are there records of routine inspections and maintenance?
Are the rainwater outlets clear?
Could leaves, debris, vegetation or contamination be restricting drainage?
Has anything changed since the roof was installed?
Have other contractors carried out work on or around the roof?
Has anyone accessed the roof?
Were suitable access routes and protection used?
Has anything been applied to the roof?
Have sealants, mastics, bituminous products, coatings or other materials been used?
Has the roof experienced severe weather?
Could recent wind or rainfall have caused damage or exposed an existing issue?
Is the roof under guarantee?
Do you know the maintenance and inspection requirements attached to the guarantee?
When was the roof last professionally inspected?
If it has been some time, an inspection may establish the cause before further damage occurs.

So, has your flat roof actually failed?

It might have. But don’t assume it has.

Water ingress should always be taken seriously, but the correct solution starts with establishing the cause.

A blocked outlet requires a different solution to a damaged membrane.

Damage caused by a subsequent contractor is different from an installation defect.

A maintenance issue is different from a material failure.

And an inappropriate repair product applied after installation can make an investigation more complicated.

That is why diagnosis comes before repair.

At Enviroply Roofing, our approach is to investigate the roof and consider the wider circumstances before recommending the appropriate course of action.

Depending on what we find, the solution could be:

clearing and maintaining drainage
removing contamination or debris
carrying out a localised repair
addressing damage
further investigation
arranging appropriate maintenance
or, where the condition of the roof warrants it, considering refurbishment or replacement

Not every leaking roof requires a new roof. In some cases an overlay or targeted repair is more appropriate once the existing build-up has been properly surveyed.

Protect your roof before a problem starts

The best time to think about roof maintenance is before water enters the building.

Regular inspections and maintenance can help identify blocked outlets, debris, damage, deterioration and other issues at an earlier stage.

It can also help building owners maintain records of the condition of the roof and demonstrate that appropriate care has been taken, which can be particularly important where a manufacturer’s or system guarantee has specific maintenance requirements.

Enviroply Roofing provides professional roof inspection and maintenance services designed to help protect roofing systems and identify potential problems before they become more serious. Read more about the advantages of a maintenance contract and commercial roof surveys.

A leaking flat roof doesn’t always mean a failed flat roof

When water appears inside a building, calling a roofing contractor is the right response.

But before assuming that the original roof installation has failed, look at the history of the roof.

Has it been maintained?
Have the outlets been kept clear?
Has debris or contamination accumulated?
Have other contractors accessed the roof?
Has the roof been damaged?
Has someone attempted a repair using a product that may not be compatible?
Have the manufacturer’s maintenance requirements been followed?

These details can make a significant difference to the cause of water ingress, the appropriate repair and, where applicable, the position under the roofing guarantee.

A roof should be investigated before it is blamed.

If your flat roof is experiencing water ingress, contact Enviroply Roofing. We can assess the condition of the roofing system, investigate potential causes and advise on the most appropriate next step.

Because sometimes the problem isn’t that the roof has failed.

It’s that something has happened to the roof since it was installed.

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