Parabit Solo Hot Melt System - Inverted Warm Roof

Sometimes referred to as an ‘upside down’ roof, the thermal insulation is positioned above the flat roof covering, resulting in the roof covering, structural deck and ceiling being at a temperature close to that of the interior of the building.

Since the insulation is above the waterproofing system the insulation must be water-resistant and it must be ballasted to prevent floatation of the insulation boards and to protect against wind uplift. Therefore, the roof deck must be capable of withstanding the additional loading of a ballasted roof.

Parabit Solo Hot Melt System - Inverted Warm Roof 

1 Ballast - Paving on Supports   6 Icopal Bitumen Primer
2 Monarperm TP160 Water Reducing Layer   7 PARABIT Hot Melt Compound
3 Thermazone Hydroshield IVR Insulation   8 Power Elastomeric 250 Sand
4 Power Elastomeric 250 Sand   9 Thermaweld Mineral Capsheet
5 Parabit Solo Membrane   10 Cement faced insulation, to upstand


Waterproofing System

Install the Parabit Solo Hot Melt Waterproofing System in accordance with the methods outlined in the Parabit Solo installation manual.

Note: Prior to application of any ballast or thermal insulation, it is recommended that the finished hot melt membrane be electronically integrity tested to ensure the roof has been thoroughly inspected, checked and passed off as being watertight.

Drainage Layer (depending upon specification)

Where rapid removal of rainwater is desired or where installing above a flat roof deck with zero falls, install an appropriate drainage board over the completed Parabit Solo membrane immediately after the leak detection test on horizontal surfaces. If testing is delayed, install a temporary covering to protect the Parabit Duo membrane from damage by other trades.

Thermal Insulation

Inverted roof insulation boards provide protection to the roof structure and waterproof coverings and reduce the stress on the membranes caused by extremes of temperature and thermal movement, while also protecting the roof from UV degradation and mechanical damage.

Surfaces should be clean and free of debris.

Inverted roof insulation boards are laid above the completed waterproofing system in a staggered, break-bond pattern ensuring all boards are laid flat and close butted to minimise cold bridging. The insulation boards should be cut accurately around any penetrations using a fine tooth saw or hot wire cutter.

The insulation boards should be laid in conjunction with a filtration (fleece) layer in an advancing manner, with appropriate ballast subsequently distributed to restrain the system.

The filter fleece must be laid with a minimum 150mm overlaps. If using Monarperm water reducing layer laps must be sealed immediately after positioning using Monobond LT double sided tape. Ensure a full seal at all joints by applying firm even pressure with a hand roller. All penetrations through the membrane should also be carefully sealed.


Ballast should be nominally 20-40mm diameter clean and smooth river-washed aggregate and installed at a depth (minimum 50mm) to prevent wind uplift or floatation of the insulation. It should be reasonably free of fines to prevent clogging of the drainage system. In some areas additional ballast of paving slabs may be required, for example around perimeters where wind uplift forces are greater.

Alternatively, ballast may be concrete paving slabs of minimum depth of 50mm and placed on suitable support spacers/pads.

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