General Construction Technology

Question 1

What is an inverted roof?

Answer 1

Also referred to as a ‘protected membrane’ or ‘upside down’ roof, is form of flat roof in which the waterproofing layer is beneath the thermal insulation rather than above it.

Question 2

What is the typical build up of an inverted roof?

Answer 2

Concrete roof slab>Liquid applied membrane (Waterproof layer)>insulating boards> weighted down with either gravel ballast/paving slabs (wind uplift/flotation)

Question 3

How does the rainwater drain away on an inverted flat roof?

Answer 3

RW percolates through/between insulation boards to the membrane where it is drained through RW outlets.

Question 4

What are the benefits of an inverted flat roof?

Answer 4

“1) Membrane is protected by insulation from thermal expansion (frost/solar).
2) Protected from foot traffic. “

Question 5

What are the drawbacks of an inverted flat roof?

Answer 5

“1) Moisture trapped between boards= risk of condensation.
2) U-Value calcs must consider that the insulation will be wet. “

Question 6

What are foundations?