Ceramic Dry Façade

What a ventilated dry façade actually is

A ventilated dry façade is two walls with a gap between them.

The inner wall does the work nobody sees: it is structural, it carries the insulation, and it is the line that keeps air and water out of the building. The outer wall — the panels — does one job. It stops most of the rain and it takes the sun, the wind and the looking-at.

Between them is a continuous gap, open at the bottom and open at the top, so air moves through it.

1. 1 · The panels screen the rain They take the sun, the wind and most of the water. They are not the weather line.
2. 2 · The cavity is open at base and head Air moves up it; whatever water gets past the panels runs down the back and out.
3. 3 · Insulation, mineral wool A1 Mechanically fixed, with the cavity measured from its face.
4. 4 · The weather line is the inner wall The barrier behind the insulation keeps air and water out of the building.

Section, outside on the left. Simplified.

“Dry” means there is no mortar, no adhesive and no wet trade anywhere in the assembly. Every panel is held by a mechanical fixing to an aluminium substructure, and every panel can be taken off again. A tile bedded in adhesive depends on a bond that ages. A mechanically fixed panel does not depend on a bond at all.

Rainscreen, ventilated façade, ventilated dry façade, rear-ventilated façade — these are the same thing under different names. Four of the five systems in this family are built this way, and what changes between them is the panel: porcelain here, natural stone, aluminium composite or high-pressure laminate. The fifth, perforated metal, is a screen rather than a rainscreen, hung in front of a wall that is already weather-tight.

The cavity does four jobs

This is the part that matters, and it is the part that gets built wrong.

1 · It breaks the capillary path. Water crosses a joint when there is a pressure difference across it and a continuous path for it to follow. The cavity removes the path. Water reaching the back of a panel has nowhere to go but down the back of the panel.

2 · It moderates the pressure. Air entering at the base and leaving at the head means the cavity sits closer to outside pressure than to inside pressure. With less pressure difference across the open joint, less water is driven through it. This is why the cavity has to be open, and why sealing it — which always looks tidier — defeats the system.

3 · It drains. Whatever does get past the panels runs down the back face and out at the base. That requires a clear path all the way down: no blocked cavity, no insulation squeezed against the panel, no horizontal obstruction without a drainage route over it.

4 · It dries. Moving air removes moisture from the outer face of the insulation and from the back of the panel. It also carries away solar heat before it reaches the insulation, which is why a ventilated façade performs better in summer than its U-value alone suggests.

• 1 · Breaks the capillary path Water that crosses the joint has nowhere to go but down the back of the panel.

• 2 · Moderates the pressure Open at base and head, the cavity sits near outside pressure, so little drives rain through the joint.

• 3 · Drains Whatever gets past the panels runs down the back face and out at the base — if nothing is in the way.

• 4 · Dries Moving air takes moisture off the insulation and carries solar heat away before it reaches it.

Sections through an open joint, outside on the left.

The specification gives 30 to 60 mm for ceramic. That is not an arbitrary range. Too narrow and the air will not move and the cavity cannot drain past bracket obstructions. Wider gives more reliable ventilation and more tolerance for an uneven substrate — and costs more bracket projection, which costs more bracket.

Design note 01, in full

The existing note says: the cavity must be open at the base and the head; a blocked cavity turns a ventilated façade into a moisture trap. Three things block cavities in practice, and all three are done with good intentions.

• Insulation installed too thick for the bracket projection, so it touches the back of the panel. The cavity depth is measured from the face of the insulation, not from the face of the wall.
• A closed base track, fitted to keep out vermin and fitted solid. The base must be vented and drained; the correct answer is a perforated closure or an insect mesh, not a solid one.
• Horizontal elements with no drainage route — a window head, a soffit, a banding detail, a change of material. Each one is a dam unless it is detailed to pass water outward and air upward.

• Insulation against the panel Too thick for the bracket projection. Cavity depth is measured from the face of the insulation, not the wall.

• A closed base Fitted solid to keep out vermin. It traps water and stops the air; a perforated closure or insect mesh does the same job and stays open.

• A horizontal element with no route out A window head, soffit or banding course. Unless it passes water outward and air upward, it collects both.

Sections, outside on the left. Each drawing shows the fault.

The build-up, from the inside out

Cavity depth

30 – 60 mm

Mineral wool, A1

50 – 150 mm

Panel thickness

10 – 20 mm

Reaction to fire

A1

Two things are worth saying plainly about that table.

The weather line is the inner wall, not the panels. People assume the visible face is what keeps the building dry. It is not. The barrier behind the insulation is. The panels are a shield in front of it. If that inversion is not understood, the joints get sealed, the cavity gets closed, and the system stops working.

The insulation is mechanically fixed and it is A1. In a ventilated cavity there is a continuous vertical air path up the face of the building, which is exactly what a fire needs. Mineral wool at A1, fixed with mechanical anchors rather than adhesive, is the conservative specification and it is the one this system is built around.

The brackets, and why they are adjustable in three directions

The substructure is an aluminium bracket fixed to the structure, carrying a T-rail that the panels clip to. The bracket is adjustable in three axes, and each axis solves a different problem.

• In and out takes up the unevenness of the wall. A concrete or block wall is built to a much coarser tolerance than a façade panel joint. The bracket is what converts one into the other.
• Up and down sets the panel course against the building’s level, which is not the same as the slab’s level.
• Along the wall sets the vertical joint line, so joints run true over the whole elevation rather than drifting.

Brackets come in two kinds and the distinction matters more than it looks. A fixed point carries the dead load of the panels and does not move. Sliding points carry wind load only and let the rail expand and contract past them. An aluminium rail restrained at both ends will bow. One fixed point per rail, sliding everywhere else, is the rule.

The bracket is also a thermal bridge. It is a metal path from the rail, through the insulation, to the structure, repeated across the whole elevation. Isolators at the bracket base are not a refinement — they are the difference between the U-value that was calculated and the U-value the building has. If the calculation ignored the brackets, it is optimistic.

• One fixed point per rail The fixed bracket carries the dead load. The rest carry wind only and let the rail expand past them. A rail held at both ends bows.

• An isolator at every bracket Each bracket is a metal path through the insulation. Isolators at its base are the difference between the calculated U-value and the real one.

Simplified.

Cavity barriers and fire

Design note 04 says cavity barriers at compartment lines are part of the façade design, not an afterthought. Here is why that sentence is on the page.

A ventilated cavity is a continuous vertical void running the full height of the building, open at the bottom, open at the top. It is an efficient chimney. Cavity barriers interrupt it at compartment lines — at floor levels and at compartment walls — so that the void does not connect one fire compartment to the next.

The problem is that a cavity barrier and a ventilated cavity want opposite things. One wants the void closed. The other wants it open. Open-state cavity barriers resolve it: they sit open in normal use, letting air and water pass, and close under heat. Which type goes where is a fire-strategy decision, and it has to be made with the façade designer rather than handed to them.

• In normal use The barrier leaves a gap at the back of the panels, so air still moves up the cavity and water still drains down it.

• Under heat The strip expands and closes the void, so the cavity no longer connects one fire compartment to the next.

Sections at a floor line, outside on the left. Schematic.

This is also where ceramic’s material class earns its place. The specification gives A1 to EN 13501-1, panel and substructure — the highest reaction-to-fire classification, meaning non-combustible. Not A2. Not “limited combustibility.” A1, for the panel and for the substructure that carries it.

On residential buildings above the height threshold in most codes, and on healthcare, education and assembly buildings in many of them, that classification is not a preference. It is the specification, and it eliminates most of the alternatives before appearance is discussed.

The base, the head and every opening

The details that decide whether a ventilated façade works are not on the typical elevation. They are at its edges.

The base. Must be open for air in and open for water out, and protected against vermin and insects — which is what a perforated closure profile or an insect mesh is for. Mesh aperture is a compromise: fine enough to exclude insects, coarse enough not to blind with dust. It also needs to be above the splash zone and above any expected snow line, and it needs to be cleanable.

The head. Must be open for air out, and covered so that water is not driven straight in. A ventilated coping or a rear-vented parapet detail does both.

Every window and door. An opening is a hole in the cavity, and water running down the cavity arrives at its head. The reveal has to collect that water and discharge it outward, over the window, not behind it. The window detail is one of the most searched details in this trade for exactly this reason: it is where the system’s two rules — always drain outward, never block the air path — are hardest to satisfy at the same time.

• The base Open for air in and water out, closed to insects with a perforated profile or mesh — above the splash zone, and cleanable.

• The head Open for air out, and covered so rain is not driven straight in. A ventilated coping does both.

• A window head Water running down the cavity arrives here. The head collects it and throws it outward over the window — never behind it.

Sections, outside on the left. Simplified.

Every horizontal interruption. A banding course, a soffit, a change of material, a balcony. Each is a potential dam. Each needs a route for water outward and for air upward.

Porcelain, not ceramic

The specification says porcelain stoneware to EN 14411, group BIa (E ≤ 0.5%). That parenthesis is the whole specification, and it is the reason the page says porcelain where the system is called ceramic.

E is water absorption, as a percentage of the panel’s dry weight. Group BIa means 0.5% or less — effectively none. Ordinary wall and floor ceramics absorb far more.

Why it matters on a façade and not indoors:

• Freeze–thaw. Absorbed water expands when it freezes. In a panel that absorbs almost nothing there is nothing to expand. In one that absorbs, the freeze cycle works on the panel from the inside, year after year. Yerevan freezes. Tehran freezes. Most of the Caucasus freezes.
• Staining and efflorescence. A dense body does not draw dirt or dissolved salt into itself. It stays the colour it was delivered.
• Colour stability. The colour of porcelain stoneware is fired, not coated. It does not have a surface layer that can chalk, fade or be scratched through.

• An absorbent body Water taken into the panel expands when it freezes and works on it from the inside, winter after winter. It draws in dirt and salts too.

• Porcelain, group BIa Absorption of 0.5% or less — effectively none. Nothing to freeze inside, nothing drawn in, and a colour fired through the body.

Sections through a panel face, exaggerated.

This is the substance behind “the conservative choice where the building has to look the same in fifteen years.” It is not a claim about quality. It is a number: E ≤ 0.5%.

One thing to specify separately. Large-format thin porcelain is normally supplied with a backing mesh for handling and for post-breakage retention. If that matters on your project — and above ground-floor level it usually does — it is a line in the specification, not an assumption.

Panel format against weight

Design note 02 says large-format panels reduce joints but increase handling weight and bracket spacing, and the two are traded against each other. The published range makes the trade concrete: 300 × 600 mm to 1,500 × 3,000 mm, at 10 – 20 mm thick, weighing 22 – 45 kg/m².

1. 1 · Large buys fewer joints A quieter elevation, fewer fixings and faster installation per square metre.
2. 2 · Large costs weight per panel A handling and safety question first, then more load into every bracket.
3. 3 · And less forgiveness Breakage is a bigger loss, and an out-of-plane wall shows more.

Panels drawn to one scale. Weights are the published 22 – 45 kg/m² multiplied by panel area.

Going large buys:

• Fewer joints, so a quieter elevation and less joint length to detail
• Fewer fixings per square metre
• Faster installation per square metre

Going large costs:

• Weight per panel, which is a manual handling and a safety question before it is an engineering one
• More load into each bracket, so heavier brackets and often closer rail spacing
• More expensive breakage — a damaged large panel is a bigger loss and often a longer lead time
• Less forgiveness on a wall that is out of plane

The honest position: format is chosen from the elevation and the handling, then the substructure is designed for it. Choosing a format because it looks right on a render and finding the bracket schedule afterwards is how the cost arrives late.

Visible clip, concealed undercut, or kerf

Design note 03 sets out the trade. Expanded:

• Visible clip Holds the panel edges from the face. No panel preparation, the cheapest, and any panel comes off from outside.

• Concealed undercut anchor Set in factory-drilled undercut holes in the back of the panel. Nothing on the face; the most panel thickness and the highest cost.

• Kerf A clip engages a groove cut into the panel edges. Between the other two on cost and thickness, but panels usually come off in sequence from an edge.

Sections through the panel edge, outside on the left. Simplified.

The line most often forgotten: demountability is a maintenance specification, not an aesthetic one. If a panel has to come off to reach a valve, a joint or a repair behind it, say so at design stage, because it eliminates one of these three options.

Overcladding: the case nobody puts on the brochure

The “Where it works” list ends with façade renovation and overclad, and on existing buildings this system does something none of the others do as well.

An old building with a poor envelope can be given insulation, a weather line, a ventilated cavity and a new elevation in one operation, fixed back through the existing wall, while the building stays occupied. No wet trades means no curing, no weather dependency and no internal disruption. The brackets’ three-axis adjustment absorbs a wall that was never flat and has moved since.

Two things decide whether it works, and both are answered before design, not during:

• Can the existing wall take the fixings? A pull-out test on the actual substrate, not an assumption from the drawings. Old concrete, old block and old brick all behave differently, and the one thing they have in common is that the record drawings are optimistic.
• Where do the windows end up? Adding 150 – 250 mm of insulation and cavity in front of an existing wall moves the face of the building outward and leaves the windows in a deep recess. Either they are replaced and moved forward, or the reveal becomes a design feature. It is not a detail that can be resolved late.

• The window stays where it was The new face sits 150 – 250 mm further out and the window ends up in a deep recess. That can be a feature, if it is designed as one.

• The window moves forward Replaced and set on the new insulation line, so the reveal stays shallow. A decision for scheme stage, not a detail for site.

Plan sections at a window jamb, outside at the top. Simplified.

What to decide, and when

1. 01

   Concept

   Ventilated dry façade or not. Which panel material — this is where the fire class filters the options, before appearance.

2. 02

   Scheme

   Panel format and joint grid. Cavity depth against insulation thickness. Where the compartment lines are, and therefore where the cavity barriers go.

3. 03

   Tender

   Porcelain group and thickness, backing mesh if required. Fixing type, which follows from the maintenance requirement. Insulation specification and fixing.

4. 04

   Production

   Bracket layout, fixed and sliding points, isolators. Base, head, window reveal and interface details. The substrate pull-out test.

What drives the cost

In order of leverage:

1 · How complicated the elevation is, not how large

Flat area is the cheap part. Every reveal, return, soffit, parapet, corner and interface is a detailed, individually engineered, non-repeating item. Two buildings of the same area can differ substantially in cost on this line alone, and it is controlled at concept stage by the architect, free of charge.

2 · The substructure, which is often more than the panel

On a ventilated façade the aluminium bracket and rail system is a large share of the cost and is invisible in the finished building. It is driven by panel weight, panel format, wind load, cavity depth and how far out of plane the existing structure is. Comparing panel prices between systems without comparing substructures compares the wrong number.

3 · Panel format and breakage rate

Large format looks efficient per square metre and is less efficient in practice on a complicated elevation, because more of it ends up cut and the offcut is waste. A panel size chosen against the elevation grid wastes far less than one chosen from the catalogue’s largest option.

4 · Fixing type

Visible clip, kerf, concealed undercut — ascending cost, in that order. The step to concealed undercut is real, because it adds factory drilling to every panel and usually requires greater thickness.

5 · Cavity barriers and fire specification

Not optional, and priced by the compartment line rather than by the square metre. Worth getting into the estimate early rather than arriving as a variation once the fire strategy is issued.

6 · Insulation thickness

Drives the bracket projection, which drives the bracket. A thicker insulation specification is not only an insulation cost.

7 · Access

The same as every façade: the building’s height and what the site can take.