Timber dormer maintenance: 2026 guide

Pine and spruce (durability class 4-5) demand the strictest paint discipline: every 4 to 6 years a full round. Faster on the south side from UV, slower on the north. Miss one round and you get visible weathering, cracks in the paint film and water penetrating under the coating — the first step to wood rot.

Meranti and larch (class 3) are more forgiving with 6 to 8 years between rounds. Untreated larch develops a silver-grey patina many find attractive; needs no paintwork but yearly inspection. Meranti is almost always painted because its open structure absorbs moisture when untreated.

Western Red Cedar and oak (class 1-2) can stand 30 to 50 years untreated. Cedar greys evenly; oak turns dark grey to black. Aesthetically a statement, but save the choice for architecture that supports the look. Painted cedar or oak follows the 8 to 12-year interval of meranti.

A proper paint job on a 3-metre dormer takes 3 to 5 working days from a professional painter. Day 1: erect scaffold or hoist (€150 to €350), remove loose paint, sand to wood (60-80 grit) and degrease surface. Day 2: local wood repairs (epoxy fill for small rot, replacement of rotted sections for larger damage), prime with touch-dry primer (2-4 hour drying).

Days 3 and 4: two topcoats of water-based frame paint (Sigma S2U Nova, Sikkens Cetol BL Forte). 4-8 hour drying between coats, light sand at 240 grit. In unfavourable weather (rain, cold below 5°C, humidity above 85 percent) coats must be skipped — painting in autumn and winter costs 30 to 50 percent more labour than spring/summer.

Ask your painter which paint system is used and keep the spec sheet. For warranty claims (5 to 10 years on premium systems) you'll need this. Cheap acrylic paints carry no stated warranty and need redoing after 3-4 years.

Eighty percent of all dormer wood rot starts on the bottom sill — where rainwater stands or lead flashing is wrongly executed. Check yearly: is there a working drip edge under the sill? Does water flow away quickly? Does a screwdriver gently pressed into the wood not penetrate? Penetration indicates rot.

Second risk zone is the frame-to-cheek connection. Sealant here weakens after 8 to 12 years and water can penetrate the corner. Replace sealant preventively every 10 years, even without visible cracks. Cost: €100 to €200 for 4 corners, quickly recovered against rot repair (€800-€1,500).

Local wood rot can be repaired early with epoxy fill (€25-€45 materials, 2-3 hours DIY or €250-€450 by painter). With advanced rot or structural damage (a bottom sill rotted 20 cm deep) the rot must be replaced with new timber profile; €450 to €900 for local replacement.

Pine 3-metre dormer over 50 years: 8 paint rounds × €700 = €5,600; 3 major overhauls × €1,200 = €3,600; ongoing inspections €1,000. Total: €10,200 maintenance.

Meranti 3-metre dormer over 50 years: 6 paint rounds × €750 = €4,500; 2 major overhauls × €1,300 = €2,600; inspections €1,000. Total: €8,100.

Cedar 3-metre dormer untreated over 50 years: yearly inspection and light clean €600; 1 major overhaul at 30 years for worn sealant and lead €1,500. Total: €2,100. (Here the purchase premium returns in lower maintenance.)

By comparison: PVC 3-metre dormer over 50 years: €500-€1,200 maintenance + 1 replacement mid-period (€6,500-€8,000) = €7,000-€9,200 total. Timber and PVC converge over lifecycle more than commonly thought; timber needs continuous attention, PVC one big investment.