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If you live in Dorset — from decking in Bournemouth to cladding installation in Verwood — the local climate plays a big role in that answer.
For many homeowners, cladding is a way to protect the property, improve insulation, and add style. But without a proper moisture cavity, even the most beautiful finish can become a costly problem. In this blog, we’ll explain what a moisture cavity is, why it matters, and how UK building regulations guide its use — especially for homes in Bournemouth, Poole, Weymouth, Highcliffe, Blandford Forum, and the wider coastal area.
Learn MoreA moisture cavity — also called a ventilation gap or drainage space — is a deliberate gap between your cladding and the wall beneath. In the UK, this gap is usually around 20 mm and is created using battens during installation.
Its main purposes are to:
Allow airflow behind the cladding, keeping the wall dry.
Provide a drainage route for any rain or condensation.
Protect the wall structure from prolonged damp exposure.
Think of it as a “breathing space” for your home. Just like your skin benefits from breathable fabrics, your walls benefit from airflow — especially when covered by a weatherproof outer layer.
Get in Touch TodayUnder Approved Document C of the UK Building Regulations, the aim is to prevent water and damp from damaging the structure. While not every cladding system has a legal requirement for a cavity, most guidance — especially in high-exposure zones like Dorset — strongly recommends it.
Key principles include:
Providing continuous drainage for rainwater.
Ensuring ventilation to remove trapped moisture.
Protecting insulation and wall materials from getting wet.
If your home is in an exposed area (and the South Coast counts as one), including a 20 mm gap is best practice — and in many cases, an expectation from local building control.
Get in Touch TodayDifferent cladding materials interact with moisture in different ways. Here’s how a cavity helps each type:
Timber is natural, breathable, and stunning — but also porous. It will absorb water if given the chance. A cavity helps it dry out quickly, preventing rot and swelling.
Highly durable and rot-resistant, but condensation can still form behind it. The cavity allows safe moisture escape.
Low-maintenance and weather-resistant, but without ventilation behind, trapped moisture can lead to unseen mould growth on battens or insulation.
Non-porous, but prone to condensation on the back surface in cold weather. The ventilation gap stops water pooling and corroding fixings.
Learn MoreFrom decking in Bournemouth to kitchens in Highcliffe and cladding installation in Verwood, we’ve worked on countless projects across Dorset. We’ve seen how homes without a cavity suffer from damp within just a few years, while those with a proper ventilation gap look as good as new for decades.
In our coastal climate, a moisture cavity isn’t just best practice — it’s a smart, protective measure for your home and all the improvements you’ve made to it.