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. If the old thermal insulating capacity in the roof is adequate, only repairs that are necessary for renewing the waterproof layer are made: levelling out impressions, improving counter-slopes. A supporting sub-structure for the waterproof layer consisting of surface layer insulation with a grooved bottom surface is used, which enables draining away moisture from the old waterproof layer layer.

If the old roof structure only needs a renewed waterproof layer and the sub-structure is of adequate stiffness, a support layer of insulation is used. Any moisture in the old waterproof layer and new moisture possibly added during the work phase will be drained by means of the grooving made by putting double layers of insulation as described below.

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Existing structure Substructure: Concrete TT slab or profile steel sheet Thermal insulation: 20 +140 mm mineral wool Waterproof layer: Bitumen or plastic based membrane      Renovation structure              Support layer: PAROC ROB 60, PAROC ROB 80 or PAROC ROS 50 or Support layer: 2x PAROC ROB 60  20 mm New waterproof membrane

When putting a separation layer on an old roof it is important that the existing roof membrane is dry. Otherwise the stone wool between tight layers will get and stay wet. To avoid problems two layers of roof slabs or board can be used.

If the old roof also needs surface reinforcement, two layers of surface layer insulation slabs are used. The longitudinal seams of the lower slab layer are left with approx. 60 mm gaps and the second slab layer forms a substructure to the waterproof layer. Thus the new waterproof layer will have a reinforced and ventilated substructure. The insulation layer grooves are led to a connecting channel at the ridge and in the elevations.

The support layer is fixed together with the waterproof layer through the insulation layer to the substructure. The mechanical fixing can also be made using fixing screws penetrating through the old waterproof layer to the insulation layer, in which case no additional holes are made in the vapour barrier.