What is an Inverted Flat Roof?

An inverted roof is a form of warm roof in which the thermal insulation is applied on top of the waterproofing layer so that the complete roof construction including roof membrane is kept at warm temperatures during the winter months and at moderate temperatures during the summer months.


Design Considerations

Inverted Flat Roof

In an inverted warm roof construction the Sika-Trocal and Sika Sarnafil (single ply membranes), Sikalastic (liquid applied membranes) or SikaBit (bitumen membranes) are installed directly to the structural deck (usually concrete). On top of the waterproofing layer, SikaTherm insulation (XPS) is installed. Then SarnaTherm Aquazone® a high performance non-woven polyethylene membrane is installed over the insulation to minimise the cooling effect associated with rainwater flowing down through the insulation and draining away. It can significantly reduce the insulation thickness. A vapour control layer is not required.

Finally, the ballast topping, such as flag stones is applied. They will allow regular foor traffic and may therefore be considered to allow the flat inverted roof to be used for recreational purposes or for locating plant and equipment.  

Our Technical Advisors carry out thermal and condensation risk analysis for every project inclusive of SikaTherm insulation. Furthermore a bespoke designed system eliminates any performance and design issues.