Do Balustrade Fixings Void Flat Roof Warranties?

Do Balustrade Fixings Void Flat Roof Warranties?

It's one of the questions that comes up most often when we're discussing roof terrace design with architects and developers: if we drill through the membrane to fix the balustrades, does that affect the waterproofing warranty?

The answer is: it can - and it's worth understanding exactly how before it becomes a problem on site.

What membrane warranties actually cover

Most flat roof membranes carry warranties between 10 and 30 years, depending on the system and the installer. Those warranties typically cover defects in materials and workmanship as applied to the membrane installation. What they don't always cover - and this is the important part - is what happens to the membrane after installation.

Many warranty agreements include specific conditions around penetrations. Some require that any fixings through the membrane are pre-approved by the manufacturer and detailed using specified collars or flashing systems. Others simply exclude penetrations from coverage. The detail varies by manufacturer and system, but the principle is consistent: the warranty covers the membrane as installed, not as subsequently modified.

Where construction sequencing creates the problem

In practice, waterproofing is almost always completed before balustrades and terrace finishes go in. That's logical from a programme perspective, but it means balustrade fixings are typically introduced after the membrane has been signed off.

If those penetrations aren't approved in advance - or aren't detailed in a way the manufacturer recognises - the warranty position on that membrane can become unclear. If a leak then develops, working out whether it's a membrane failure or a penetration failure, and who carries responsibility, can get complicated quickly across multiple trades.

This is a fairly routine feature of how terraces get built and it's one of the reasons liability disputes around terrace defects tend to be messy.

Where careful detailing matters and where it still has limits

Where penetrations are unavoidable, proper detailing is non-negotiable: proprietary flashings, approved collars, sealant specified by the membrane manufacturer. Done correctly, these details can hold up for many years.

But they still represent a maintenance liability. They need periodic inspection and they're vulnerable to the same thermal movement, UV degradation and structural loading that affect any sealant-dependent detail. Even a well-installed penetration is a point of future risk in a way that an unbroken membrane is not.

Avoiding the problem rather than managing it

For this reason, a number of architects we work with now prefer to avoid membrane penetrations altogether where there's a viable alternative. BalcoDeck® was developed partly in response to that preference. By keeping the balustrade and decking structure above the membrane rather than anchored through it, the membrane stays continuous and the warranty complications that come with drilled fixings don't arise.

For terraces above occupied space, where the cost of a leak extends well beyond the terrace itself, that matters.

Download the BalcoDeck® brochure here.