Flat Roofs

Question 1

What makes a roof a flat roof?

Answer 1

A pitch of less than 10%

Question 2

What is a cold deck flat roof?

Answer 2

A type of flat roof construction where the deck is cold, meaning that the insulation is below the structural member.
Cold roofs require ventilation or a vapour control barrier to prevent condensation in the roof void and underside of the roof covering. Vents can be a good indicator of a cold roof

Question 3

What is a warm deck flat roof?

Answer 3

A type of flat roof construction where the deck is warm, meaning that the insulation is above the structural member.
Ventilation is not required as the insulation keeps the deck warm, so no condensation will be produced. Vapour control layer provides extra protection to the structural elements. Solar protection required, and insulation is at risk of damage from foot traffic

Question 4

What is an inverted flat roof?

Answer 4

A flat roof construction where the structural member is waterproofed, and the insulation sits above the waterproofing, secured with ballast.
Good for areas where foot traffic is required. Insulation can be easily upgraded. Difficult to detect leaks, inspection of waterproofing membrane requires removal of ballast and insulation

Question 5

What elements need to be considered in a roof covering warranty?

Answer 5

• Insurance backing
• Materials only vs design and construction
• Maintenance/inspection requirements
• Assignation/beneficiary

Question 6

What types of detection methods are available if a leak to a flat roof is not immediately apparent?

Answer 6

• Electronic leak detection; where an electrical field is created on the material, and any points where there is “earthing” to the building can pinpoint penetrations
• Thermal imaging; where cold areas of water penetration can be tracked
• Endoscopes; can be inserted into a void to review structure

Question 7

At what point does a refurbishment of a roof covering require to have a thermal upgrade?

Answer 7

If 25% of a roof is being refurbished, then Part 7 of the Building Regulations requires the thermal properties of the roof to be improved

Question 8

What is reinforced bitumen membrane, and how is it applied?

Answer 8

RBMs are waterproofing membrane systems constructed from bonding layers of RBM with bitumen. Often there are reinforced with polyester, which extend the lift span and resilience.
Application can be pour & roll, torch on or self/cold adhesion. Torch on most common (doesn’t require bitumen kettle, does require Hot Works Permit)

Question 9

What is a single-ply membrane, and how is it applied?

Answer 9

Single-ply membranes are polymeric single-ply membranes, provided in single sheets which provide waterproofing materials.
They can be mechanically fixed, fully adhered or loose laid and ballast held onto a roof surface

Question 10

What type of lead would you expect to find on a flat roof?

Answer 10

Code 5 rolled lead sheet, likely with standing seam installation