Are we ignoring water as the biggest threat to buildings?

Ask most people in construction what keeps them awake at night and you’ll hear the same answers about fire risk, structural failure, programme schedules and rising costs. They are all valid and serious. but there’s another threat - quieter, less dramatic and far more persistent. It’s called water and this is the one that causes more damage to buildings than almost anything else, writes John Ridgeway.

We are not talking about floods or storms. It is everyday water that causes the damage. Rain that finds its way in. Condensation that builds up unnoticed and leaks that go unresolved. It’s the kind of water damage that doesn’t make headlines, but quietly destroys buildings from the inside out.

The damage we don’t talk about

Water is responsible for a huge proportion of building failures. Insulation becomes saturated and loses performance. Timber elements begin to decay, steel corrodes and finishes fail. Mould then develops, bringing health risks and reputational damage and unlike fire or structural collapse, this doesn’t happen suddenly - it happens slowly, gradually and often invisibly. All this makes it far easier to ignore, until it becomes expensive to fix.

The Building Research Establishment has long identified moisture ingress as one of the most common causes of building defects in the UK. Insurance data tells a similar story, with escape-of-water claims consistently among the highest in both frequency and cost. This isn’t a niche issue, it’s systemic.

Why water is winning

So why are we still getting it wrong? Part of the problem is how we design. Modern buildings are more complex than ever. Multiple layers, interfaces, systems, are materials all needing to work together perfectly to keep water out and allow moisture to escape, but such complexity increases risk.

Every junction becomes a potential failure point. Every penetration is a weakness if not detailed correctly and every trade introduces another variable. Too often, these details are either poorly resolved at design stage, or compromised during construction.

Speed, cost and consequence

Then there’s the pressure to build quickly and cheaply. Tight programmes mean less time to get details right. Value engineering can strip out resilience, but substitution of materials introduces unknowns. Perhaps most critically, testing and verification often fall short.

This is because we assume systems will perform. We rely on drawings rather than reality and move on before performance is proven. Water doesn’t care about any of that., because It will always finds the weakness.

The buildings we can’t see

There’s also a deeper issue, when what happens after handover. Most water-related problems don’t appear during construction. They emerge later, when the building is in use.

Roof membranes degrade, sealants fail, drainage systems block and condensation builds within walls or roof voids. Facilities teams are left to manage issues that were often designed in from the start and because the damage is gradual, it’s rarely treated with urgency, until it escalates.

A blind spot in sustainability

Here’s where the conversation becomes even more uncomfortable. As the industry pushes towards sustainability, we’re focusing heavily on carbon, materials and energy performance.

They are all important, but what’s the environmental impact of a building that fails early due to water damage? If insulation becomes saturated, thermal performance drops.
If components decay, they need replacing. If systems fail prematurely, the whole-life carbon equation collapses. Durability is the real sustainability and water is one of the biggest threats to durability.

Mass timber and the warning signs

The debate around mass timber has brought this issue into sharper focus. Concerns about moisture ingress, whether from construction, occupancy or even fire suppression, highlight just how sensitive some modern materials are to water. But this isn’t a timber problem, it’s an industry problem.

If water can compromise performance to this extent, then we need to be far more honest about how we design, build and maintain buildings in a moisture-rich environment like the UK.

So what needs to change?

First, we need to stop treating water as a secondary risk. It should be central to design thinking andnot an afterthought.

That means:

• Better detailing at interfaces
• Greater emphasis on buildability
• More robust testing and verification
• Clear accountability for performance

It also means designing for maintenance. Buildings should be accessible, inspectable and repairable. Because water-related issues are not a question of if, but when.

We are not talking about floods or storms. It is everyday water that causes the damage. Rain that finds its way in. Condensation that builds up unnoticed and leaks that go unresolved. It’s the kind of water damage that doesn’t make headlines, but quietly destroys buildings from the inside out.

The damage we don’t talk about

Water is responsible for a huge proportion of building failures. Insulation becomes saturated and loses performance. Timber elements begin to decay, steel corrodes and finishes fail. Mould then develops, bringing health risks and reputational damage and unlike fire or structural collapse, this doesn’t happen suddenly - it happens slowly, gradually and often invisibly. All this makes it far easier to ignore, until it becomes expensive to fix.

The Building Research Establishment has long identified moisture ingress as one of the most common causes of building defects in the UK. Insurance data tells a similar story, with escape-of-water claims consistently among the highest in both frequency and cost. This isn’t a niche issue, it’s systemic.

Why water is winning

So why are we still getting it wrong? Part of the problem is how we design. Modern buildings are more complex than ever. Multiple layers, interfaces, systems, are materials all needing to work together perfectly to keep water out and allow moisture to escape, but such complexity increases risk.

Every junction becomes a potential failure point. Every penetration is a weakness if not detailed correctly and every trade introduces another variable. Too often, these details are either poorly resolved at design stage, or compromised during construction.

Speed, cost and consequence

Then there’s the pressure to build quickly and cheaply. Tight programmes mean less time to get details right. Value engineering can strip out resilience, but substitution of materials introduces unknowns. Perhaps most critically, testing and verification often fall short.

This is because we assume systems will perform. We rely on drawings rather than reality and move on before performance is proven. Water doesn’t care about any of that., because It will always finds the weakness.

The buildings we can’t see

There’s also a deeper issue, when what happens after handover. Most water-related problems don’t appear during construction. They emerge later, when the building is in use.

Roof membranes degrade, sealants fail, drainage systems block and condensation builds within walls or roof voids. Facilities teams are left to manage issues that were often designed in from the start and because the damage is gradual, it’s rarely treated with urgency, until it escalates.

A blind spot in sustainability

Here’s where the conversation becomes even more uncomfortable. As the industry pushes towards sustainability, we’re focusing heavily on carbon, materials and energy performance.

They are all important, but what’s the environmental impact of a building that fails early due to water damage? If insulation becomes saturated, thermal performance drops.
If components decay, they need replacing. If systems fail prematurely, the whole-life carbon equation collapses. Durability is the real sustainability and water is one of the biggest threats to durability.

Mass timber and the warning signs

The debate around mass timber has brought this issue into sharper focus. Concerns about moisture ingress, whether from construction, occupancy or even fire suppression, highlight just how sensitive some modern materials are to water. But this isn’t a timber problem, it’s an industry problem.

If water can compromise performance to this extent, then we need to be far more honest about how we design, build and maintain buildings in a moisture-rich environment like the UK.

So what needs to change?

First, we need to stop treating water as a secondary risk. It should be central to design thinking andnot an afterthought.

That means:

• Better detailing at interfaces
• Greater emphasis on buildability
• More robust testing and verification
• Clear accountability for performance

It also means designing for maintenance. Buildings should be accessible, inspectable and repairable. Because water-related issues are not a question of if, but when.

The uncomfortable truth

Fire is catastrophic, but rare. Water is constant. It doesn’t destroy buildings overnight.
It degrades them over time and that makes it far more dangerous, because it’s easier to ignore.

The question we should be asking

If we’re serious about building performance, durability and sustainability, we need to rethink our priorities. Not just how we design buildings to stand up, but how we design them to stay intact.

Because until we take water seriously, we’re not building resilience, we’re building risk.

The uncomfortable truth

Fire is catastrophic, but rare. Water is constant. It doesn’t destroy buildings overnight.
It degrades them over time and that makes it far more dangerous, because it’s easier to ignore.

The question we should be asking

If we’re serious about building performance, durability and sustainability, we need to rethink our priorities. Not just how we design buildings to stand up, but how we design them to stay intact.

Because until we take water seriously, we’re not building resilience, we’re building risk.