Rain Screen Systems

What a Rain Screen Is

A rain screen is a wall built on the assumption that some water will always get past the outer surface. Rather than relying on a single sealed skin to stop everything, the assembly is designed to catch that water, drain it back out, and dry the cavity between wetting events.

The outer cladding is the first line of defence, but it is not the waterproofing. Behind it sits a ventilated and drained cavity, and behind that a continuous air and water-resistive barrier applied to the substrate. That barrier is the actual weatherproofing layer. Water that penetrates the cladding runs down the back face, hits flashing, and exits through weeps at the base of the cavity.

This matters because face-sealed walls fail in a specific way: they depend entirely on sealant joints, and sealant has a finite service life. When a joint fails on a face-sealed wall, water enters the building with nowhere to go. When a joint fails on a rain screen, the water lands in a cavity built to drain it.

System Types & Components

Principle

Outer skin sheds most water
Ventilated and drained cavity
Air barrier on the inner wall

Cladding

Glass and ceramic frit panels
Aluminium composite and plate
Terracotta, stone and porcelain

Fixing

Concealed or exposed brackets
Thermally broken helping hands
Stainless fixings throughout

Compliance

NFPA 285 assembly testing
Perimeter fire barrier
Design pressure by elevation

Why a Rain Screen Is Not Waterproof

A rain screen wall is designed on the assumption that water will get past the outer skin. That is not a compromise; it is the principle the whole system is built on.

The outer cladding sheds the great majority of water. Behind it sits a ventilated and drained cavity. Behind that is the real weather line: a continuous air and water barrier on the face of the structural wall. Anything that gets past the cladding runs down the cavity and drains out at the base.

Compare that with a face-sealed wall, which relies on a continuous line of sealant to keep every drop out. Sealant fails, and when it does there is no second line. The rain screen has two.

Pressure Equalisation

Water is driven through a gap by a pressure difference. Wind pressing on a facade pushes water through any opening it finds, which is why wind-driven rain finds its way into buildings that handle ordinary rain perfectly well.

A pressure-equalised rain screen vents the cavity so the air pressure inside it matches the pressure outside. With no pressure difference across the cladding joints, there is very little force driving water through them. Compartmenting the cavity — dividing it vertically and horizontally so pressure equalises locally rather than across a whole elevation — is what makes this work on a tall building.

The Parts That Actually Fail

The air barrier. It is the real weather line and it is buried behind the cladding. If it is discontinuous at a slab edge, a penetration or a corner, the wall leaks and nobody can see where. It has to be continuous and it has to be inspected before the cladding goes on, because afterwards it is inaccessible.

Cavity drainage. Blocked weeps at the base mean water stands in the cavity. Mortar droppings, sealant and insulation debris during construction are the usual causes.

Thermal bridging at the brackets. Every bracket holding the cladding passes through the insulation. Steel brackets conduct, and a facade full of them can lose a surprising proportion of its insulation value. Thermally broken brackets exist for this reason and are worth specifying.

Movement. Panels expand and contract through a temperature range far wider than the air temperature, as our waterproofing page explains. Joints have to accommodate it or the panels buckle and the fixings elongate.

The Compliance Item That Stops Projects

Exterior wall assemblies on buildings above a certain height are subject to NFPA 285 fire propagation testing, and it is the assembly that is tested, not the individual products. Substituting a cladding panel, an insulation type or even a membrane for an apparently equivalent one can invalidate the tested assembly.

This catches projects late and expensively. The time to confirm the assembly is at specification, not when a substitution is proposed on site.

Where Rain Screens Are Used

These describe the kind of work each area brings rather than any specific client project.

New residential towers — Long Island City, Downtown Brooklyn, Greenpoint. Increasingly the default exterior wall on mid and high-rise construction, frequently combined with curtain wall at the glazed elevations.

Hudson waterfront — Hoboken, Jersey City, Weehawken. Severe wind-driven rain off open water, which is precisely the condition pressure equalisation exists for. Cavity compartmentation matters more here than almost anywhere.

Facade recladding — older commercial and institutional buildings citywide. Where an existing wall has failed, a rain screen over a new air barrier is often the durable answer. Facade inspection requirements frequently drive this work.

Coastal — the Rockaways, Staten Island's shores, the Jersey Shore. Salt on every fixing. Stainless of the correct grade, and dissimilar metals isolated.

Send us the elevations, the design pressure and any assembly specification you have been given. We work across Manhattan, Brooklyn, Queens, the Bronx and Staten Island, and throughout Northern New Jersey, the Jersey Shore, Philadelphia and the Lehigh Valley.