Cladding Preparation Hub

UV light degrades the surface lignin in the wood, turning it silver. It’s natural, but if you want the "new wood" colour back, you need to use a Wood Reviver/Brightener to chemically strip this grey layer.

Not always. Sanding is hard work on vertical walls. A chemical clean (Wood Reviver) is often enough to open the grain. However, if the wood is "glazed" (shiny) or very rough, a light sand (80-120 grit) helps the oil penetrate.

Knots contain resin that bleeds through standard primers. You must spot-prime every knot with a dedicated "Knotting Solution" or a shellac-based primer before applying your main undercoat.

Black spots are often a reaction between water/iron and the tannins in the wood. Oxalic Acid is the specific cure for this—it neutralizes the tannin stain and bleaches the black spot back to natural wood.

Be very careful. "Standard" solvent cleaners can melt or dull the surface of PVC if left on too long. Always use a "Garden/Paper" safe solvent or a specific PVC cleaner designed for cladding, not just industrial frames.

This is dirt and algae washing over from blocked gutters. The rubber seals degrade and drip carbon deposits down the wall. You need a dedicated degreaser to remove them; water alone won't work.

Yes, but prep is vital. You cannot just paint glossy plastic. You must abrade the surface lightly with a Scotch-Brite pad to key it, clean it with a solvent cleaner, and use a specialist UPVC primer or a paint designed to bond to plastic.

This is deep UV degradation of the plastic itself. Cleaning won't fix this. If the plastic has yellowed through, your only option is to paint it or replace it.

We strongly advise against it. High pressure can etch the surface, opening it up to moisture and permanent staining. Use a garden hose and a soft brush instead.

No. Sodium Hypochlorite (Bleach) can discolour the pigments in composite, leaving pale patches. Use a "DDAC" based biocide which is pH neutral and safe for plastics.

Composite is porous to oil. You need to act fast with a hot water degreaser. If the stain is old, it is very difficult to remove without damaging the board surface.

No. Unlike wood, if you sand composite, you destroy the textured finish and expose the inner core material, which will absorb water and swell.

This is "Chalking." The UV light has destroyed the binder in the paint. You must pressure wash this off until the water runs clear. Do not paint over chalky surfaces.

It is where the factory coating peels back from the edge of the metal sheet, exposing the steel to rain. It effectively eats the sheet from the edge inwards. You must grind this back to bright metal and seal it.

Not directly. Fresh galvanising is greasy and too smooth. You must use "T-Wash" (Mordant Solution) to turn the metal black/grey (etching it) before you can apply any primer.

Masking is 50% of the job. You must cover all skylights, windows, and adjoining brickwork. Overspray travels far on windy days. Ensure the cladding is bone dry before spraying.

Only with specific paints. You must scrape off loose flakes first. Then, use a "Barrier Primer" or a Barn Paint specifically formulated to handle bitumen bleed. Standard masonry or gloss paint will turn brown and slide off.

Wire brush the loose flakes (flaking rust) until you have a solid surface. You don't need to get to bright shiny metal, but the loose scales must go. Then apply a "Rust Converter" or a direct-to-rust metal paint.

Do not pressure wash. Use a high-strength biocide. saturate the moss, let it die (it turns brown), and allow the weather to wash it off over a few weeks. Scraping or blasting releases dangerous fibres.

Yes. Livestock urine creates Ammonia, which attacks paint. You must wash the walls down with an "Acid Etch" or a strong detergent and rinse thoroughly to neutralize the surface pH before painting.