PVC dormer maintenance: 2026 guide

Twice a year (spring and autumn) a light clean keeps a PVC dormer crisp for years. Use a soft brush or microfibre cloth with lukewarm water and a dash of neutral soap. No aggressive descalers, scouring pads or solvents — these attack the UV-protective layer and accelerate yellowing.

Frames and corners need extra attention because dust, pollen and exhaust gases collect there. A telescopic brush with soft-bristle pad reaches most 2 and 3-metre dormers up to 6 m height from the ground. For higher or wider dormers hire a window cleaner: €150 to €300 for a full treatment including glass and frames.

On dark colours (anthracite, black) stains and white deposit show faster. Clean 3 to 4 times a year for optimal look. After cleaning a PVC polish (Lecol PVC Polish, about €15) restores the UV layer and prevents water spots. Once a year is enough for most situations.

Check all sealant joints around frames, corners and the connection to the roof. Shrinkage cracks or peeling sealant strip are the earliest signs of ageing. Replace local strips (1 to 2 m): DIY €15 for the sealant, or contractor €150 to €350 including removal of old sealant and deep clean.

Inspect the lead flashing (the connection between dormer and roof tiles). Lead greys and slightly folds — that's normal. What's not OK: cracks, holes or a sagging connection where water can run under. Repair €450 to €900 including scaffold or roof ladder.

Test window operation: open, close, locks and hinges. Lubricate moving parts with silicone spray (€8); replace worn gasket if you feel a draught or rubber feels brittle (€25 to €50 per window, easily done DIY).

Check drainage: gutter full of leaves? Rain water flowing? A blocked gutter on a dormer causes leakage along the connection within one wet autumn. Clean gutter yearly (€0 DIY, €75 to €150 by roofer).

Problem 1: green deposit on north side. Algae and moss grow on damp shaded surfaces. Clean with diluted chlorine cleaner (HG Algae & Moss Cleaner, €12) — not with pressure washer which damages UV layer. Treatment once every 2-3 years.

Problem 2: discolouration (yellowing on south, greying on north). On standard PVC visible after 20 to 25 years. Not fixable by cleaning; only by overpainting with PVC primer + plastic paint (€350 to €600 for 3 metres, not always durable). On premium HPL (Trespa) discolouration appears only after 40 to 50 years.

Problem 3: deformed or warping panels, especially south on dark colours. An expansion issue from heat absorption. Not repairable; only preventable by always choosing heat-resistant PVC or HPL for dark colours. Single panel replacement: €450 to €900 installed.

Problem 4: sagging or loose trim profiles around the frame. Aluminium trim can rattle or come loose after 10-15 years. Re-glue with adhesive sealant (€10) usually suffices; severe cases need contractor replacement (€200 to €400 per strip).

A well-maintained PVC dormer lasts 30 to 40 years. After that multiple problems combine: discolouration, shrinkage cracks across the sealant system, sagging connections and dated colour or style. At that point full replacement is often cheaper than repair because material and labour savings on a new element outweigh stacked repair jobs.

The tipping point sits around €3,500-€4,500 in stacked repairs within 3 years. Above that, replacement with a new prefab (€5,000-€7,500 for 3 metres) is economically logical, especially because you can also upgrade insulation from old R 2.0 to modern R 6.3, with matching energy saving and label uplift.

For homes you plan to sell within 5 years a middle route can be attractive: cosmetic refresh (replace sealant, restore lead, clean) for €600-€1,200. Makes the home more saleable without full investment.