Mass timber and water - are we asking the right questions?

"Why sprinkler water - not fire - is mass timber's greatest threat" was the original headline of a recent research article. Take a moment with that headline. A system that keeps fires small is being positioned as a greater danger than the fire itself. The claim attracted enough concern that the article was subsequently revised, but the framing had landed and deserves a direct response, writes Tom Roche, Secretary of the Business Sprinkler Alliance.

The research behind it, published by Halliwell Fire Research on behalf of the Fire Protection Research Foundation, examines how mass timber buildings perform after a sprinkler-suppressed fire.

Stop and think about what that original headline was actually claiming. If a system that intervenes early, limits fire growth, and controls structural damage is now being treated as a problem in itself, what would be proposed in its place? The fire service will attend but they arrive later, when a fire is larger, and the volumes of water they deploy are far greater. If the concern is water ingress into CLT connections, the answer is not fewer sprinklers. That path leads to more water, applied to a building far more seriously damaged by fire.

Jim Glockling, Visiting Professor at UCLAN and a respected voice in fire engineering, made exactly this point in response to the research on LinkedIn. The right comparison, he argued, is not sprinklers versus nothing. It is the small, targeted volumes that sprinkler heads local to the fire put down very early, when the fire is still small, versus the quantities the fire service might apply late in an event when the fire is bigger and may have spread. On that basis, he concluded, “To this end I see fire sprinklers as an essential component of water damage reduction, not the problem - quantities are small and known and easily recovered from.”

The moisture challenge that follows suppression is real and worth investigating seriously. Better post-fire drying protocols, connection detailing that reduces water trapping, and clearer assessment procedures are all productive directions. But these are design and management refinements. They sharpen how we use active fire protection, they do not make the case against it.

There is, however, a much deeper issue here. If mass timber is sensitive enough to water that post-fire sprinkler discharge warrants this level of concern, what does that tell us about the water risks already present in these buildings which go unnoticed?

Plumbing and drainage failures, condensation within structural elements, roof and cladding water ingress, escape-of-water events. These carry no sprinkler activation, no incident report, no obvious trigger for investigation.

If water sensitivity in mass timber is the concern, that is where the headlines should be directed, not at the systems protecting us from fire.

As the construction sector embraces mass timber for its environmental credentials and structural qualities, we must be honest about the additional layers of protection these buildings require. The use of combustible materials in innovative construction introduces fire risks that, if not addressed with equal care, can undermine all the gains made in sustainability. That balance can be struck but only when resilience is valued alongside the other objectives we are designing for.

Sprinklers are not the problem, as this research reveals. They are part of the answer to a set of questions the mass timber sector is beginning to ask properly. The question we should now be asking is not how we protect buildings from their own suppression systems, it is how to make the most of the active fire protection systems that need to be installed.