Do I need a membrane under uPVC cladding?
It depends on the wall. On a timber frame, fit a breather membrane behind the battens. On a masonry cavity wall in sound condition, a membrane is often not needed. Solid walls without a cavity need a waterproof coating or, better, a breathable membrane. Always follow the cladding maker’s guide.
Why is the wall type the deciding factor?
Cladding is a rainscreen, so some water gets behind it. The wall behind has to deal with that moisture. Timber frame is vulnerable to damp, so it needs the membrane. A masonry cavity wall already has its own barrier.
What should the membrane be?
- Breathable (vapour open), so the wall can dry out
- Lapped and fixed so water runs off
- Taped or protected where battens are fixed through it
What goes with the membrane?
Treated battens over the membrane, then closures at the base and top to keep insects out while allowing airflow. Fix battens with external-grade fixings into studs where possible on timber frame. If the wall is damp or has defects, put them right before cladding.
MLI Building Products stocks cladding and fixings for trade customers in Worthing, with free delivery within 30 miles.
Need a trade price? Call the trade counter on 01903 262 636 or visit us at Unit 1, Friar Walk, Worthing. We offer free delivery within 30 miles.
← Back to Trade Counter FAQs | See our trade counter products
