Cold Bridges in Flat Concrete Roofs

Ray Dow

Hi all,

With regard to concrete flat roofs, where the concrete deck passes over a 300mm cavity wall, what is the recommended form of construction for preventing a thermal bridge through the concrete deck? (if any)

I have seen a number of manufacturer details (such as the attached) which recommend; roof membrane on insulation on VCL on conc. deck but I can't figure out how this type of construction would prevent a cold bridge and condensation forming on the soffit of the concrete internally.

Thanks in advance for any guidance.

Ray

BryanF

• the conc slab stops at the inner leaf
• the cavity insulation is continuous to meet the roof insulation

Ray Dow

Thanks Bryan. I'm assuming the outer leaf is carried up to the take the timber supports then.

I don't know why this particular manufacturer is recommending this type of construction for their product - could have been an expensive repair job down the line.