What is a Warm Roof?

  • In a warm roof the thermal insulation is immediately below the membrane finish
  • The structural deck, any voids and the ceiling are at a temperature close to that of the building’s interior
  • Condensation control is achieved by using a vapour control layer (VCL) on the warm side of the insulation
  • The amount of insulation should be enough to maintain the VCL above dewpoint temperature
  • Warm roof voids are not ventilated
  • Condensation can be calculated to BS 6229 and BS 5250


In a warm roof construction the Sika-Trocal membrane and INNObond thermal insulation is installed above the structural decking. In principle this keeps the structural deck (usually trapezoidal steel or timber) at more or less the same temperature as the inside of the building A vapour control layer is required underneath the insulation in to prevent moisture vapour being transmitted from the building outwards where it could condensate in the roof construction  (interstitial condensation). 

Warm roofs are generally considered as very effective for energy use reduction and building performance. However the thermal insulation type and thickness is critical.  Sika-Trocal carry out thermal and condensation risk analysis for every project. Furthermore a bespoke designed system eliminates any performance and design issues.   

What makes up a Warm Flat Roofs?

Image: Sika-Trocal Warm Roof System Build Up
Sika-Trocal Warm Ballasted Roof System Build Up
Image: Sika-Trocal Warm Ballasted Roof System Build Up