Flat Roofs

Question 1

What defects would you expect to find in a roof covered with Reinforced Bitumen Membranes?

Answer 1

• Splits and tears (main body of roof); caused by movement to substrate/thermal movement, or over bonding to substrate
• Blister (below or between layers); caused by a lack of solar protection, or water vapour pressure below roof covering
• Dents/punctures; caused by physical damage
• Lifting at joints; cause by insufficient bonding or thermal movement close to joint
• Softening of surface (localised); cause by contamination by oil

Question 2

What treatment options are available for split and tears to a RBM roof covering?

Answer 2

If thermal movement, installation of expansion joints.
If substrate movement, if movement is likely to be ongoing, lifts and re-laying providing a patch to back joint, so that joints in substrate match with joints in RBM can provide additional flexibility.
If over-bonding, minor patch repairs may be sufficient. Otherwise, lifting and replacement may be required.

Question 3

What treatment options are available for blisters to a RBM roof covering?

Answer 3

If localised and caused by water vapour pressure, then vents can be installed. If minor, and in an older installation, it can be left as the materials are prone to cracking from brittleness cause over time. May require replacement
If caused by lack of solar protection, solar chips or UV protective paint. If over time, replacement may be required

Question 4

What treatment options are available for dents/punctures to a RBM roof covering?

Answer 4

Patch repairs with torch-on materials

Question 5

What treatment options are available for lifting at joints to a RBM roof covering?

Answer 5

If caused by thermal movement, additional expansion joints could be installed.
If lack of bonding, re-bonding by torching or a large patch over the area

Question 6

What treatment options are available for softening of the surface to a RBM roof covering?

Answer 6

If caused by oil contamination, requirement to cut out effected area, ensure area is stable and replace

Question 7

What defects would you expect to find to a flat roof covered with a single-ply membrane?

Answer 7

Electronic Leak Detection works really well with single-ply and can be used to accurately locate punctures. Common defects include:

• Very susceptible to puncture damage (due to single thin sheet)
• Cracking/shrinkage; cause by age
• Distortions (ridges and mounds); usually caused by issues with the substrate, specialist investigation recommended
• Failure of laps; generally poor workmanship

Question 8

What treatment options are available for puncture damage to a flat roof covered with a single ply membrane?

Answer 8

Localised temporary patch repair with appropriate material (single ply not torch on), and then replacement of effected area. Limiting foot traffic, and installing walkways to prevent further damage recommended

Question 9

What treatment options are available for cracking or shrinkage to a single ply membrane?

Answer 9

Either replacement due to end of economic life. If shrinkage only, splicing with a new section of single ply membrane may prolong life

Question 10

What treatment options are available for distortion to single ply membranes?

Answer 10

Caused not by an issue with the single ply membrane itself. Repairs to substrate likely required.

Question 11

What common defects would you expect to find in a flat roof covered with mastic asphalt?

Answer 11

• Surface imperfections; caused by lack of solar protection
• Cracking (penetrating); cause by differential on the asphalt surface, or between asphalt and substrate
• Distortion; caused by differential thermal movement, exacerbated by a lack of solar protection
• Blistering; caused by trapped moisture, exacerbated by lack of solar protection

Question 12

What treatment options are available for surface imperfections to a mastic asphalt roof covering?

Answer 12

Additional solar protection should be considered. Minor surface imperfections can be left alone.

Question 13

What treatment options are available for cracking to a mastic asphalt roof covering?

Answer 13

If water ingress present, then investigation into condition of substrate will dictate extent of remedial works. Patch repairing to cracked areas may be sufficient. All areas of removal and replacement should be warmed and cut.

Question 14

What treatment options are available for distortion to a mastic asphalt roof covering?

Answer 14

Minor cases, or non-critical areas may not require remedial works. Addition of solar protection can prevent further issues in early cases. Full replacement may be required depending on severity

Question 15

What treatment options are available for blistering to a mastic asphalt roof covering?

Answer 15

Small blisters can be left alone. Large blisters suggest further issues. If from trapped construction moisture, simple repair will be sufficient. If from interstitial condensation, cause will need to be eliminated prior to repair or fault will persist

Question 16

What defects would you expect to see on a lead sheet flat roof?

Answer 16

• Cracking; caused by incorrect code of lead for application, or inappropriate underlay, or incorrect spacing of joints/too many soldered joints
• Dents; cause by physical damage
• Lifting of sheets at edges; caused by insufficient fixings
• Pitting, corrosion or staining; caused by presence of an incompatible material or exposure to condensation

Question 17

What are the treatment options for cracking to a lead sheet roof covering?

Answer 17

If wrong code, then temporary patch repairs, followed by replacement with a higher code.
If inappropriate underlay, lifting and replacement underlay and re-laying of lead sheet should be carried out.
If joints, may require additional joints or replacement of soldered joints with laps or welt joints

Question 18

What are the treatment options for dents to a lead sheet roof covering?

Answer 18

Removal of the risk of damage, or increase the code of the lead. Dents can be patch repaired with lead and soldered joints

Question 19

What are the treatment options for lifting at edges of sheets to lead sheet roof coverings?

Answer 19

Increase number of fixings. Replacement with higher code lead sheet should be considered.

Question 20

What are the treatment options for pitting, corrosion and staining to lead sheet roof coverings?

Answer 20

Remove water stream or treat condensation to prevent ongoing corrosion and staining. Replacement of lead sheet may be required depending on extent of damage.

Question 21

What defects would you expect to find on a zinc roof?

Answer 21

• Reaction to atmospheric pollution causing surface corrosion
• Reaction to copper water run off
• Reaction to acidic woods (in roof structure), causes corrosion to underside of sheet

Question 22

What defects would you expect to find on a copper roof?

Answer 22

• Reaction to pollution, bird droppings and coastal condition (plumbers can do repairs)

Question 23

What defects would you expect to find on a steel roof?

Answer 23

• Miss identification as lead, as it can be turn-coated to look like lead
• Reacts with irons