What to look out for when buying a dormer?
The four most important points: 1) check the provider supplies an itemised quote with every line listed separately, 2) request three quotes to compare fairly, 3) check whether insulation, ventilation and finish are included, and 4) read references or visit a sample project.
Itemised quote
A quote without breakdown is incomparable. Ask for separate items for: structure/trimmer, roof element, frames + glass, insulation (with Rc value), cladding (with material and colour), roofing, ventilation, interior finish, crane hire and VAT.
Permits and Building Decree
Check yourself whether you are permit-free (see /vergunning/dakkapel-vergunningsvrij). The provider is not liable for your permit obligation. When in doubt: call the municipality or run a permit check via Omgevingsloket.
Insulation and ventilation
A dormer without proper insulation (minimum Rc 4.5 m²K/W for wall and roof) becomes hot in summer and draughty in winter. The Building Decree also requires this. Ventilation grids are mandatory for fresh air — not optional.
References and warranties
Ask the builder for two or three reference addresses you may visit or call. Also ask explicitly about the warranty period on structure, frames, glass and waterproofing — these can differ.