Flat-roof insulation (interior)

Insulating a flat roof from the inside — via the underroof: ± € 40-90 per m², roughly € 1,500-5,000 per job.

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If you have a living space under a flat roof — an extension, a roof addition or the top floor of a 1960s/70s home — it can be insulated from the inside. The installer fits insulation against the underside of the roof (the underroof) and finishes the ceiling afterwards. The roof covering stays intact and nothing has to come off the roof.

Expect roughly € 40 to € 90 per m², which for an average floor comes to € 1,500 to € 5,000 per job, including labour, materials and finish. Important with a flat roof: a proper approach accounts for damp and ventilation, so no condensation forms between the insulation and the roof. So mention any damp or leak marks on the ceiling in your request — the company then assesses the cause first.

Here too: this is the inside. A flat roof that is due for replacement is often insulated on the outside when the covering is renewed — and that is a roofer's job, not a service of this site.

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