Can Commercial Cladding Be Coated?
Which cladding types are coatable, which require specialist treatment, and what determines substrate suitability for spray-applied refurbishment.
6 min read
- Most commercial cladding types are coatable — substrate identification determines the correct primer system.
- Steel and aluminium require different primer chemistry — applying the wrong primer is a common cause of adhesion failure.
- Substrate structural condition, not surface appearance, is the primary determinant of suitability.
- Multiple existing coating layers do not automatically preclude refurbishment, but affect preparation requirements.
What Types of Cladding Can Be Coated?
Most commercial cladding types used on UK industrial and commercial buildings are suitable for spray-applied refurbishment, provided the substrate is structurally sound and the coating system is correctly specified for the substrate. The main cladding types and their suitability are:
- Pre-coated profiled steel (polyester or plastisol): Widely coatable. Standard preparation — pressure washing and mechanical abrasion — provides adequate key for a compatible primer and topcoat system. The most common substrate type on UK commercial buildings.
- PVDF-coated steel: Coatable but requires specific primer chemistry to achieve adhesion to the PVDF surface. Standard wash primers used on polyester substrates will not adhere adequately to PVDF. Substrate identification is essential before specification.
- Galvanised steel: Coatable with appropriate zinc-compatible primer. Standard solvent-based primers can cause delamination on galvanised substrates. Surface preparation by sweep blasting or chemical treatment is required.
- Mill-finished or anodised aluminium: Requires chemical etching primer — mechanical abrasion alone does not provide adequate adhesion on aluminium surfaces. Anodised aluminium may require additional surface preparation to key the anodised layer.
- Composite insulated panels (outer steel skin): Generally coatable where the outer steel skin is structurally intact. Assessment must include joint condition, insulation integrity, and whether the panel system has fire safety implications that restrict surface treatment.
- Fibre cement: Coatable with appropriate masonry-compatible systems. Less common on commercial buildings but present on some educational and healthcare facilities.
What Makes a Substrate Unsuitable?
Structural failure of the substrate — perforation, delamination, or loss of structural integrity — makes coating treatment alone inappropriate. Coating cannot restore structural performance. The following conditions indicate the substrate requires more than coating treatment:
- Perforation of profiled steel sheets from cut edge or surface corrosion.
- Delamination of composite panel outer skins from the insulation core.
- Significant corrosion thinning of the steel substrate (beyond surface rust).
- Saturation of composite panel insulation with moisture.
How Does Existing Coating Condition Affect Suitability?
The condition of the existing coating affects preparation requirements, not necessarily suitability. Heavily chalked coatings require more thorough preparation than lightly faded ones. Failed or delaminating coatings require more intensive mechanical preparation. In extreme cases — where multiple existing coating layers have failed and cannot be adequately prepared — the preparation cost may approach or exceed the cost of an alternative approach.
Multiple existing coating layers (more than two or three refurbishment coats over the original factory coat) do not automatically prevent further over-coating, but do require assessment of the total system thickness and adhesion through all layers.
Substrate identification must precede system specification. Applying a primer system designed for steel to an aluminium substrate, or a standard wash primer to PVDF, will result in adhesion failure — typically within 1–3 years — regardless of how well the surface was prepared or how good the topcoat is.
The question "can it be coated?" is almost always answerable with "yes, if..." rather than a definitive yes or no. The conditions that make coating viable are substrate integrity, correct system specification for the identified substrate, and achievable preparation standard — not simply whether the cladding looks suitable from the ground.
The cases where we advise against coating are where the substrate condition means the coating system will not achieve its expected service life — and where coating would therefore create a false sense of security without addressing the underlying condition.
Frequently Asked Questions
How do I identify my cladding substrate type?
Visual inspection by an experienced assessor can usually identify substrate type from profile, surface texture, and coating appearance. Where uncertainty exists, material sampling or testing may be required. Substrate type determines primer selection — it is not a detail that can be assumed.
Can I coat over existing paint that is still adhering well?
Yes, where existing coating adhesion is sound. Adhesion testing (pull-off test or cross-hatch test) confirms whether the existing coat provides an adequate base. Where adhesion is confirmed, the existing coat becomes part of the system build-up.
Does the cladding age matter?
Age matters in so far as it indicates the likely condition of the existing coating and substrate. Cladding from the 1980s is more likely to have cut edge corrosion issues and degraded factory coatings than cladding from 2010. Age is an indicator for what to assess, not a determinant of suitability in itself.
Can PVDF cladding be colour-matched?
Yes. Colour matching for PVDF substrates follows the same process as other substrates — RAL or BS reference matching, or sampling from an unexposed area. PVDF's greater UV stability means original colours are often better retained, which can make matching easier.
Related Guidance
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