Pitched Rood Coverings

Question 1

Construction detailing

Answer 1

Question 2

Roof tiles layout – not waterproof

Answer 2

Question 3

Roof tiles layout – waterproof

Answer 3

Question 4

Traditional mortar bedded Vs wet bed in details - wet

Answer 4

Question 5

Traditional mortar bedded Vs dry bedded details – dry

Answer 5

Question 6

Loads and pitched roof coverings.

Dead loads:

Answer 6

Question 7

Loads and pitched roof coverings.

Imposed loads:

Answer 7

Question 8

Loads and pitched roof coverings.

Wind loads:

Answer 8

Question 9

Tile battens

Answer 9

Normally 38×25 mm or 50×25 mm cross-section depending on the weight of the roof covering and the spacing of the rafters

Question 10

Spacing of the tile battens up the roof slope

Answer 10

Relates to the tile/slate size and the amount of lap required by the respecification – the spacing of the buttons is called the “gauge” of the roof

Question 11

Flashings

Answer 11

The height of this vertical overlap is normally a minimum of 75 mm

Question 12

Flashing detail diagram

Answer 12

Question 13

Roof covering details. Main Ridge/hip ridge

Answer 13

Question 14

Typical roof covering details.

Eaves

Answer 14

Question 15

Typical roof covering details.

Verge

Answer 15

Question 16

Typical roof covering details.

Abutments

Answer 16

Question 17

Typical roof covering details.

Abutment at head of slope

Answer 17

Question 18

Typical roof covering details.

Chimneys

Answer 18

Question 19

Typical roof covering details.

Chimney back gutter

Answer 19

Question 20

Typical roof covering details.

Sloping valley gutter

Answer 20

Question 21

Typical roof covering details.

Junction above flat roof

Answer 21

Question 22

Typical roof covering details.

Parapet gutter

Answer 22

Question 23

Roof tiles.

Plain clay tiles and plain concrete tiles

Answer 23

• Concrete plain tiles have a life expectancy of about 60 years
• Clay tiles have a life expectancy of over 100 years
• Minimum pitch for most tiles of this type is 35°

Question 24

Roof tiles

Interlocking concrete tiles

Answer 24

Can be laid to a low pitch of 12.5°

Life expectancy of about 60 years

Question 25

Roof tiles

Welsh and other slight

Answer 25

Good quality slate class well over 100 years, larger sizes can be laid down to 20°

Question 26

Roof tiles

Fibre cement slate

Answer 26

Lifespan in the region of 30 to 50 years.

Has a square cut edge

Question 27

Roof coverings

Metal roof coverings

Answer 27

Lead – 60 to 100 years lifespan
Zinc sheet - 80 to 100 years lifespan
Copper sheet roof – lifespan 80 years

Question 28

Roof coverings.

Thatch life expectancies

Answer 28

Question 29

Pitched roof coverings – pathology

Answer 29

The whole process can be divided into three overlapping stages:

1) identify the defects by investigation
2) determine the cause by analysis
3) confirm remedial action required

Question 30

Common reasons why pitched roof coverings fail:

Temperature

Answer 30

• Expansion (increasing temperature)
• Contraction (decreasing temperatures)
• Water may be driven off (evaporated) drying material out
• Volatile component of roof material evaporate – changing performance characteristics of remaining material
• Freezing/thawing of water

Question 31

Thermal movement to lead cover flashing

Answer 31

Question 32

Cyclical temperature change and freezing of water

Answer 32

Lower quality clay tiles can absorb water which at greater risk of spalling and frost damage

Question 33

High temperatures week any materials inherent strength

Answer 33

Dark roof materials can exceed 80°C.

Bitumen products softener, losing strength

Question 34

Low temperatures making material inflexible/brittle

Answer 34

Cold roofing materials are less flexible, some materials will become more brittle including plastic verge trims in a dry bed tile system.
Adjacent details including parapet walls are at greater risk of the freezing/thawing cycle causing is spalling

Question 35

Subsequent inappropriate alterations

Answer 35

Question 36

Subsequent inappropriate alterations 2

Answer 36

Question 37

Aging of materials - hessian reinforced bitumen underlay

Answer 37

Question 38

The range of defects affecting a pitched roof covering eight divided into a few areas:

Answer 38

Question 39

Reporting, some of the things you need to include for the client are:

Answer 39

Question 40

Reporting, some of the things you need to include for other professionals/contractors are:

Answer 40