The framework behind HPL cladding determines how long the facade lasts more than the panel does. A premium sheet on a corroding, badly spaced frame will bow, sag and eventually fail. This is the line item most often cut, and it is the wrong one to cut.
What the Framework Does
It carries the panel weight and wind load into the building structure, holds the panels in a true plane, and creates the ventilated cavity that lets moisture drain and evaporate. All three functions matter.
Material Options
Mild steel (MS)
The cheapest option and widely used. MS is strong and easy to fabricate, but it corrodes. Untreated MS in a humid or coastal environment will rust, and rust at fixing points compromises the whole assembly. If MS is used, it must be properly primed and painted, and even then it is not the right choice for aggressive environments.
Galvanised iron (GI)
MS with a zinc coating, giving considerably better corrosion resistance at moderate extra cost. This is the sensible middle option for most residential projects and is what we would recommend as a default over bare MS.
Important caveat: cut ends and drilled holes expose bare metal. These need treating, or the corrosion simply starts there instead.
Aluminium
The most corrosion-resistant and lightest option, and the standard for quality commercial facades. More expensive per metre, but it does not rust, weighs less, and typically outlasts the cladding itself.
Recommended for coastal locations, high-rise projects, and any building where re-access for framework repair would be difficult or expensive.
Spacing
Framework spacing must match panel thickness, panel size and wind exposure. A common starting point for 6mm panels is around 600mm centres in both directions, but this is a guideline, not a specification.
Widening spacing to save on framework is a false economy. A 6mm panel spanning too far will deflect visibly in direct sun, and no amount of panel quality compensates for that.
For your specific project, spacing should be confirmed against the panel manufacturer’s technical data and, on anything substantial, checked by an engineer for wind loading.
The Ventilated Cavity
The air gap between the wall and the back of the panels is functional. It allows any water that gets past a joint to drain out, lets moisture evaporate, and reduces heat transfer into the building.
Cavity requirements:
- Depth — typically 25 to 50mm; follow the system specification
- Open at the base — so water can drain out; screen against vermin but never seal
- Open at the top — so air can flow through, driving evaporation
- Unobstructed — do not pack insulation into the cavity without dedicated provision for drainage and airflow
A blocked cavity converts a well-designed rainscreen into a water trap.
Anchoring to the Building
Anchors must reach sound substrate. On a wall with thick or delaminated plaster, an anchor that only grips the plaster will pull out under wind load. Check substrate quality during survey, not during installation.
Use corrosion-resistant anchors and fasteners throughout. Mixing metals unnecessarily can also cause galvanic corrosion at contact points, so keep the system consistent where possible.
Allowing for Movement
Both the framework and the panels expand and contract with temperature. The system needs to accommodate this through slotted fixing points and expansion gaps at panel edges. Rigid fixing at every point is a common cause of bowing.
Frequently Asked Questions
What is the best material for HPL cladding framework?
Aluminium for coastal, high-rise and long-life projects; GI as a solid default for most residential work. Bare MS is the cheapest but the least durable.
What spacing should the framework be?
Around 600mm centres is a common starting point for 6mm panels, but confirm against the manufacturer’s data and your wind loading.
Can I install HPL directly onto the wall without a framework?
Not recommended. Direct fixing eliminates the ventilated cavity, prevents drainage, and gives the panel no room to move with temperature.
How deep should the cavity be?
Typically 25 to 50mm, and it must remain open at both base and top for drainage and airflow.
Need framework guidance for your project? Contact our technical team with your wall details and panel specification.