Before designing the roof renovation, the present condition of the roof and the scope of damage need to be inspected. Generally roof renovations are initiated when the waterproof layer needs to be renewed.  

At the same time you can also upgrade the roof functionality by improving drainage and thermal insulation. Energy savings obtained by additional insulation are more substantial, the lower in the old structure the insulation layer is. (See also www.paroc.com/Structures/Flat roofs/ Energy saving calculator).

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Calculate your required additional insulation for roof using this calculator! The program calculates your insulation profitability with adequate accuracy.

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Existing structure Substructure: Concrete TT slab or profile steel sheet Thermal insulation: 50 +70 mm mineral wool Waterproof layer: Bitumen or plastic based membrane      Renovation structure              Additional inclination layer: dry expanded clay pellets Additional thermal insulation: PAROC ROS 30g (grooved), PAROC ROB 80 (PAROC ROB 50, PAROC ROB 60) New waterproof membrane

For the additional thermal insulation, use grooved sub-layer insulation in order to gradually drain any moisture from the old waterproof layer. The old waterproof layer is left intact to function as an air barrier against any air leakage. The additional insulation thickness should be at least the same as in the old structure in order to obtain the present thermal performance requirement. A good "rule of thumb" is to give the renovated roof the same status as a new one. This insulation is of significance also for energy saving. Additional insulation increases temperature in the old structure and thus promotes its drying. When renewing eaves structures the elevation required by the additional insulation can be implemented as well as connecting the insulation grooving to the elevations.

In the renovated roof the additional insulation layer functions as a sub-structure for the new waterproof layer. If the old structure is soft, use more rigid insulation types for additional insulation, for instance PAROC ROS 30g and the surface layer insulation PAROC ROB 80.

The mechanical fixing of the additional insulation and the new waterproof layer requires long fixing screws. When fixing the screws in the concrete sub-structure, the expanded clay pellets may penetrate into the pre-drilled screw holes. If using profile steel sheets, special accuracy is also required when directing the fixing screw in the profile steel sheet ridges.