How to renovate a roof

Roof insulation can be 25 to 40 cm thick. The exact type and thickness of the insulation depend, among other things, on the existing building. Older buildings have either slanted roofs (trussed), mansard roofs (also trussed) or flat roofs.

For insulating rafter roofs, there are the options of over-rafter, between-rafter and below-rafter insulation, or two or three of these options are combined in order to achieve the thickest possible insulation.

There are various ways of insulating rafter roofs: doubling, attaching thick planks laterally, (half) I-sections or suspension.

For over-rafter insulation, the roof structure is doubled upwards.

Example of a roof structure with insulation over rafters (source: www.Holzfragen.de, Sachverstän-digenbüro für Holzschutz Hans-Joachim Rüpke / Dr. Ernst Kürsten Hannover, adapted)

Example of a roof structure with insulation over rafters (source: www.holzfragen.de, Sachverständigenbüro für Holzschutz Hans-Joachim Rüpke/Dr. Ernst Kürsten Hannover, adapted)

For a proper roof structure the individual layers have to be matched to each other.

For between-rafter insulation, insulation is installed between the roof rafters.

Below-rafter insulation is installed from inside.

Flat roofs are renovated through doubling. Either the new insulation layer is placed on the old insulation layer, or the entire insulation is replaced.