The polyester dormer: monolithic and seamless

Single-mould or hand-layup production allows flowing curves, slanted faces and fully seamless transitions. No silicone seams to fail, no panels that shift. The exterior gel-coat (0.5-0.8 mm thick) is the same layer used on sailing yachts: extremely UV- and salt-resistant.

Structurally polyester is stronger than PVC at comparable thickness (tensile strength 60-80 N/mm² vs 40-50 for PVC), so walls stay thinner and there's more room for insulation. But polyester has higher thermal conductivity than PVC; achieving Rc requires more insulation core (PIR or EPS).

Production is more labour-intensive than PVC extrusion; 2-3× more manual work per element. Hence higher price and smaller batch sizes. The Netherlands has only 8-12 specialist polyester-dormer makers, mostly based in Zeeland and Noord-Holland.

Virtually maintenance-free for the first 15-20 years. After that polish gel-coat every 8-10 years (€200-€400 by specialist) to keep gloss. On discolouration or matting of gel-coat: re-coating with polyester topcoat possible (€650-€1,500 for 3 m), extending life 15-20 years.

Impact damage repairs excellently with polyester kit (€150-€300 by specialist, €30-€60 DIY for small scratches). Advantage over PVC: local repairs become invisible thanks to gel-coat method. Drawback: fewer specialists in the Netherlands — for repair you may have to travel 100+ km for a craftsman.

At end of life (35-45 years) full replacement is standard. Polyester is moderately recyclable; currently 25-40% is reused as reinforcement fibre in new composites. Production CO2 footprint is higher than PVC, but long lifespan and low maintenance largely compensate.

Coastal areas within 5 km of sea (Scheveningen, Texel, Vlieland, Terschelling, Schiermonnikoog, Walcheren, Schouwen-Duiveland) where salt mist breaks down PVC sealants in 5-10 years. Polyester gel-coat is the most reliable choice here; the €1,500-€2,500 surcharge pays back in maintenance savings.

Modern architecture with curves, slants or non-orthogonal geometry. PVC and timber are limited to flat panels; polyester allows free form. Architects in Amsterdam, Rotterdam and Eindhoven pick polyester for distinctive looks on modern villas and lofts.

Ask specifically for 'textured gel-coat' for less visible soiling (glossy polyester is dust- and algae-prone). Also ask for insulation package: polyester elements have less insulation room than PVC frame builds, demand Rc ≥ 4.7 with PIR core.

Consideration 1: weight. Polyester is heavier than PVC (650-950 kg for 3 m vs 450-650 PVC). For older houses with light roof framing this can mean structural reinforcement (€500-€1,500 surcharge). Always require a structural report before signing.

Consideration 2: crane logistics. Higher weight requires a heavier crane (€100-€250 surcharge on crane hire). In narrow streets (Amsterdam centre, Den Haag-Scheveningen village) a mobile telescopic crane may be needed instead of standard truck-loader.

Consideration 3: supplier market. Only 8-12 specialist makers in the Netherlands. Request at least 2 references from projects 10+ years old in your region. Avoid 'general' dormer suppliers who deliver polyester as a side product — craftsmanship matters significantly with polyester.