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Flat roofing > Flat Roofing > Flashcards

Flat Roofing Flashcards

1
Q

What is the life expectancy of built up roofing

A

10-30 years

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2
Q

What are the bases for built up roofing

A

Organic felts
Asbestos,
Fibreglass
Polyester felts

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3
Q

How many plies in a built up roofing

A

2-5

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4
Q

How is built up roofing installed on a roof

A

First layer of felt is nailed to the deck before asphalt is applied . This prevents leakage through the roof board and causing a fire .
It is not counted in the number of plies in BUR

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5
Q

Why will felt and mopping not last for 20 years

A

Asphalt is good waterproofing material but it deteriorated at uv exposure and the volatiles are boiled out
Aggregate is added for uv protection

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6
Q

What are the aggregates used for built uproofing

A

Asbestos
Marble
Rock slag
Gravel
Crushed stone

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7
Q

Where is the gravel embedded

A

In the flood coat of hot asphalt.

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8
Q

Why should the gravel be dry before being embedded in the flood coat

A

Wet gravel will not adhere to the asphalt and will deposit moisture to the roof membrane

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9
Q

What other functions of gravel in a built up roofing

A

Hold the membrane down
Fire protection to the roof
Reflect suns heat and light

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10
Q

Do roofs covered with decks require gravel

A

No
Deck provides uv protection
Act as ballast and
Keeps roofs cooler

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11
Q

Is it ok to instal a new membrane over a old built up roofing

A

No.
It adds weight to the structure
Water may be trapped in the old membrane

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12
Q

How to find out the number of layers in a built up roofing

A

Number of drip edging may be more than one
Look at the perimeter of the roof

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13
Q

How are blisters formed in built up roofing

A

Air or water trapped between roof sheathing and membrane
Air or water trapped between plies and membrane
Air or gasses ( such as solvents ) trapped in the asphalt

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14
Q

Should you walk on spongy roofs

A

Yes to find out blisters
These can be cut open, dried, sealed and recovered with gravel

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15
Q

What is alligatoring

A

A hot sun leads to the volatiles boiling off. When it’s cold and the membrane shrinks a characteristic alligator skin pattern is formed
Overtime the crack deepen and eventually allow the water to enter the felt through the asphalt

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16
Q

Where wooden decks are placed on flat roofs why do door sills leak

A

Poor flashing at the door sill
Door sills should be at least 6 “ above deck NOT roof surface

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17
Q

What are fishmouths in built up roofs

A

Fishmouths are caused when ridged or wrinkled felts are opened at the edge
They are caused by twisting the felt during application

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18
Q

What is the implication of ridges and fishmouths

A

Water is wicked into the membrane
The gravel may migrate away from the ridge

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19
Q

Why do built up roofing membranes slip

A

Due to gravity and the type of asphalt on a slope and delamination in hot weather
Type 1 flows more easily than type 2
Type 2 flows more easily than type 3

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20
Q

What are the other causes of delamination in built up roofing

A

Asphalt layer too thick
Unusually hot temperature
Overheated asphalt on installation
Felt layer not well secured to roof deck

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21
Q

How long should water be in a place to call ponding

A

48 hours

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22
Q

What are the causes of ponding in flat roofs

A

Poor design
Saggin of the structure
Poor drainage

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23
Q

What are the implications of ponding

A

Shorten life of membrane
Sagging of the structure
Damage to the building

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24
Q

What are the implication of debris on a built up roofing on a flat roof

A

Pierce the membrane
Add to live load causing deflection
Impede drainage

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25
Q

What are other names for Modified bitumin

A

Polymer modified bitumin
MODBIT
Rubberized asphalt

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26
Q

What is the life of a MODBIT

A

12-20 years

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27
Q

What is the minimum slope for MODBIT

A

1/4 by 12

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28
Q

How many types of MODBIT are there

A

APP: a Atactic polypropylene
SBS: styrene Butadyne Styrene commonly called as rubberized asphalt

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29
Q

Is MODBIT asphalt compatible

A

Yes

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30
Q

How does MODBIT provide UV protection

A

Granular surface
Liquid applied latex
Foil surface: Al or copper ballast

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31
Q

How is MODBIT installed

A

Torced on
Mopped in with hot asphalt
Peel and stick

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32
Q

What is synthetic rubber

A

Commonly called synthetic rubber
This can be vulcanized or non vulcanized elastomers

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33
Q

Example of synthetic rubber

A

EPDM

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34
Q

Does EPDM require uv protection

A

No

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35
Q

What is the size of an EPDM sheet

A

50 ft wide

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36
Q

How is EPDM to the secured on the roof

A

1.contact cement or
2. Mechanically by Bars or buttons
3. Laying it loose and holding it down with ballast

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37
Q

Can EPDM be bonded with hot asphalt

A

No

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38
Q

Effect of oils and water from AC leaks

A

Roof mounted AC leak oil onto the roof damaging the EPDM

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39
Q

What flashings are used on EPDM

A

Epdm

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40
Q

What is the life expectancy of epdm

A

20 years

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41
Q

What causes tenting in EPDM

A

Too taught because of
shrinkage
Sheet expansion during hot whether
Insufficient allowance for membrane relaxing prior to installation

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42
Q

What is the effect of oils on EPDM roofs

A

Discolouration

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43
Q

What are the most common failures on EPDM roofs

A

Openings at the seams or flashings

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44
Q

Give examples of plastic roofing

A

PVC

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45
Q

What does PVC feel like

A

Swimming pool vinyl liners

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46
Q

Do you need gravel on pvc roofs

A

No

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47
Q

Is pvc compatible with asphalt

A

No

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48
Q

Is pvc compatible with polystyrene

A

No

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49
Q

How is pvc secured to the roof deck

A

Contact cement
Mechanical fasteners
Securement strips

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50
Q

What is the size and thickness of pvc

A

5-10 ft wide
69-100 ft wide thickness 0.8mmyo 1.5 mm

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51
Q

What are the flashings for pvc roofs

A

Upvc or pvc clad metal

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52
Q

Should you walk on pvc roofs

A

No if temp is 10 degree c

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53
Q

Is pvc effected by air pollution or uv radiation

A

Yes

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54
Q

Life of pvc

A

20 years

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55
Q

What is the life of roll roofing

A

5 years

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56
Q

What is another name for roll roofing

A

Selvage

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57
Q

Do flat roofs shed water

A

Like all roofs there has to be a slight slope

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58
Q

In concealed fasteners is it better to use nails or screws

A

Screws are better

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59
Q

Function of base and counter flashing

A

They make the transition from the membrane to the adjoining material ie mask art wall or metal stack

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60
Q

What is a can’t strip

A

Triangular blocks of wood that allows a 90 degree turn to 2 45 degree turn s as membrane goes up the wall

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61
Q

How is it a good idea to use a can’t strip

A

Less cracking at the change in direction

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62
Q

what is a base flashing, where is it located ho.

A

The base flashing makes a watertight joint to the roof membrane and extends up the wall to a point well above the expected depth of water . It is usually 8-14 inches above the roof deck.

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63
Q

Is base flashing secured to the wall,

A

No

64
Q

What materials are base flashings made up of

A

Roofing felts
Fabric reinforced asphalt products
Modifies bitumens
Synthetic rubber ie neopreneplastics
Various modifications of the above

65
Q

If a tar and gravel roof ends in a stop without any curbs then what prevents the gravel from falling off
Or what is a drip edge flashing

A

The membrane is typically turned down over the edge of the roof and a drip edge flashing is attached on it .this drip edge has a horizontal component which covers the membrane on the roof and the end of the wall.it is then raised 1/2 “ to 3/4 “ tall. It then drops and covers the vertical membrane again for 3-6 inches

66
Q

How is the gravel stop secured to the roof and wall?

A

At the roof a metal drip edge flashing it is generally screwed or nailed at the vertical and horizontal part of the roof and wall respectively

67
Q

How is the metal drip edge flashing sealed after nailing or screwing.

A

the flashing is set in hot asphalt or cold mastic and then the top surface is mopped in with 1-2 strips of roofing felts set in hot asphalt . This is about 4 inches beyond the inner edge of the metal.
Where the roof has a curb the membrane is usually carried over the curb and a base flashing of of roofing felts is mopped into the top surface of the roof as well as the top of the wall . The base is covered with a metal counter flashing that forms the drip edge.

68
Q

How is a metal edge flashing installed on a ePDM or modbit ie single ply instead inorganic felt

A

1.The roofing membrane is extended down over the roof,
2.the metal drip is secured in place,
3.and the horizontal surface is covered with a strip of the roofing material.
4. This covers the entire horizontal section of the drip edge flashing and extends 4” back towards the centre of the roof.
5.This may be glued, mopped in hot asphalt or torched in inorganic felt

69
Q

How else do roofs end

A

roof ends terminate against walls that are higher than the roofs ie one storey garage with a flat roof may be attached to a two storied house

70
Q

What flashings are used when a flat roof meets with a wall

A

Base flashing and counter flashing

71
Q

What’s a can’t strip

A

To make the membrane less susceptible to cracking a can’t strip is placed at the junction of the roof and wall.
It’s a 3” by 3” wooden piece to allow a 45 degree turn
The roof membrane extends on the can’t strip but not up to the vertical wall surface .

72
Q

What’s the base flashing

A

Often it’s the roof membrane itself
It extends out into the flat portion of the membrane and is sealed to it there.
It extends up and over the can’t strip onto the vertical strip 8-14 “ above the roof

73
Q

What is the counter flashing when a flat roof meets a wall

A

One is A reglet.
the metal extends down over the top of the base flashing and is secured into the masonary by one inch or more

74
Q

What’s another counter flashing

A

A two piece counter flashing.
The top part is permanently set into the wall and the other is removable

75
Q

What’s a hem

A

Where a bottom edge of the counter flashing turned under to form a hem
This eliminates sharp edges and makes the bottom of the flashing more rigid

76
Q

Do roofs and walls move

A

They do and can pull apart the best installed flashing details

77
Q

What is the elegant solution to prevent damage due to roof wall movement

A

Create a 8-10 inch wooden wall on the roof next to the wall. Installing a giant strip and base flashing are laid in place with the base running up the mini wall . The counter flashing is then attached to the cant strip and the reglet in the wall . This is for normal walls

78
Q

What if the roofing is MODBIT pvc or epdm

A

Same as earlier but cant strips cannot be used on epdm and pvc because they shrink considerably under circumstances
However fastening strips or termination bars can be used to pinch the roofing down to the roof deck or into the bottom of the wall before the base and roof membrane are installed

79
Q

What are coping’s in parapet walls

A

If the wall is short then the base flashing is extended up the wall and over it . The counter flashing is extended to form a cap for the top of the parapet wall. The outer face of the coping also forms a drip edge flashing.
Copings can also be in stone , concrete or terra Cota

80
Q

Does the parapet wall drain inside or outside

A

The entire height of the wall is protected from wetting with metal .
The metal cap flashing is secured on the outside by a terminator bar and on the inside it overlaps the counter flashing which islet into the mortar.

If it’s a single ply roofing system it is extended above the wall and drains water away from the wall outside

81
Q

What flashings are used on chimneys

A

Base and counter flashing

82
Q

How much should a chimney cap extend above the chimney face

A

1 inch

83
Q

On a flat roof what should be the height of the curb for a skylight

A

8 inches

84
Q

What is a pitch pan or pitch pocket in stacks

A

It’s a three x3 inch metal box which covers the I beam or irregularly shaped penetration on the roof,
it is stripped into the roof with stack flashings. They are filled with cold asphalt mastic.
This material tends to shrink, dry out and crack. It leaks then
Pitch pockets require lot of maintenance

85
Q

How are internal drains connected to a pipe

A

The flange is at the top of the pipe and the sleeve extends down below the membrane inside the roof drain in the building
The roof membrane is laid up to the edge of the drain opening. The 3 inch flange is set into the membrane and then stripped in

86
Q

Where are scuppers installed

A

Primary scupper at the elevation of the membrane and secondary scuppers 2 inches above

87
Q

If Flat roof draining into sloped roof what steps are taken to prevent leakage

A

Step one :On the roof sheathing a 4 ply membrane is spread which runs horizontally across the horizontal surface and then vertically down . It is secured to the vertical end by a terminator bar,
Step two :
On top of the membrane 1-2 layers of felt are mopped over the horizontal surface .
Step 3
A metal gravel stop is secured between these two moped surfaces for 4 inches, rises to become a metal gravel stop and de ends vertically to end in a hem for added rigidity,the hem presses against the shingle

88
Q

What if it’s the opposite- ie steep roof that drains onto flat roof below

A
  1. The FLAT roof membrane should extend about 3 feet up under the STEEP roofing shingles or tiles
  2. Depending on the material the steep roof shingles may extend down to the flat membrane
  3. if rigid material or tiles are used they should not contact the membrane for fear of tearing it during differential building movement
  4. If metal flashing is extended up the steep roof by a few inches . If that is the case the top of the metal is overlaid by the shingles or tiles
89
Q

What conditions cause flashings being pulled away by membrane

A

Cooling in epdm and pvc due to shrinkage

90
Q

Which words mean the same

A

Mastic is roofing
Cement is asphalt
Cement is plastic cement
All are applied with a trowel

91
Q

Why do leaks show up some distance in the interiors from the failure point

A

Water May travel horizontally along plastic vapour barriers before coming through the ceiling

92
Q

What is the life expectancy of Built up roofing

A

10 years

93
Q

What is the life expectancy of roll roofing

A

5 years

94
Q

What is the life expectancy of MODBIT

A

12-20 years

95
Q

What is the life expectancy of clay tiles

A

100 years

96
Q

What is the life expectancy of neoprene flashing

A

10-20 years

97
Q

What is the life expectancy of lead flashings

A

30 years

98
Q

What is the life expectancy of epdm

A

20 years

99
Q

What is pvc not compatible with

A

Asphalt

100
Q

What is epdm not compatible either

A

Asphalt

101
Q

If adjacent chimney wall is made of asphalt then how to secure it

A

By securing a reglet

102
Q

How many types of flashings can u find on chimneys

A

Three
Side top
Bottom

103
Q

What causes effervescence at base of chimneys

A

Leeching of materials from the masonary , this can be in the glue or the outer surface of the chimney
Does best by waterproofing the flashing

104
Q

Do we describe roofs

A

no we only inspect them

105
Q

With what material is TPO is incompatible with

A

Like EPDM and pvc - TPO is incompatible with asphalt

106
Q

Which sidings act as a counter flashing to keep material from rotting

A

Wood
Aluminum
Vinyl
Stucco

107
Q

Why does leakage in a roof see a distance away from the point of leakage

A

Plastic water vapour travels some distance before condensation

108
Q

What is copings

A

When there is a roof top it’s top is protected by a metallic counter flashing which directs the water away from the roof

109
Q

What is a bar clamp

A

A bar clamp secures the shingle or a flashing against the surface. Its second to a reglet which is inserted into the mortar and caulked

110
Q

What are the causes of roof sagging

A

Excess weight of material ie asphalt or station or debris
Weight of snow
Water ponding

111
Q

How is a curved tile flashed

A

Pan flashing ie
It has a curled lip 1/4 to 1 1/4 of an inch’ placed away from the roof intersection with wall
It runs along with the flashing furthest away from the wall
Creates a metal trough between the wall and the tile
The inner curve of the tile is supported by this upraised lip

112
Q

How much should the base cap of the chimney flashing should go into the roof

A

4-12 inches

113
Q

What are up stands

A

In valleys are raised surfaces to divert water in two streams or specially where one side of the roof pours more water than the otger

114
Q

Are exposed nails used in valleys

A

Never

115
Q

Which sides wear off fast

A

South and west due to uv rays

116
Q

Which is the best Eve protection in order of priority

A

1.Mod bit
2 .metal sheathing
3.Polyethylene
4.roof felts
5.roll roofing

117
Q

At what distance are fasteners used to secure membrane on built up roofing’s

A

12 inches apart with 2 nails close every three inches

118
Q

Where are avalanche guards commonly found

A

Slate
Clay
Concrete

119
Q

When are sidings used as counter flashing to keep wood from rotting or soaking

A

Wood
Al
Vinyl
Stucco

120
Q

Role of ridges

A

Protection
Venting

121
Q

Other name for netal

A

Galal me
Galvanized steel
Zinc
Copper
Terne
Tin

122
Q

Other name for single ply roof

A

PVC
MODBIT
Poll roofing

123
Q

How is counter flashing secured to a mortar wall

A

Metal bent at the end and end is secured through mortar as a reglet.

124
Q

What are the problems of clay tiles at ridges

A
125
Q

What is pvc not comparability with

A

Asphalt

126
Q

What is Al not comparability with

A

Mortar

127
Q

How are skylights sealed

A

Hermetically or vented

128
Q

What material is used in solariums

A

Glass
Wood
Metal

129
Q

Where is the maximum problems in solariums

A

First wall solarum interface
Then joints with glass
Then kitchen
Then glass tops

130
Q

After valley flashing where is the other leakage
Penetration
Then slash points
Then roof joints and then skylights

A
131
Q

If condensation is more uniform and widespread then what is it due to

A

It’s a winter problem only

132
Q

If the condensation is concentrated then what’s the cause

A

Due to rain

133
Q

What flashings are used in dormers

A

Step flashing on sides
Cap flashing on top
Base flashing on botyom

134
Q

Which roofs have cap flashings

A

Asphalt and metal roofs have ridge caps or hip caps

135
Q

Role of ridges in venting

A

Allows escape of hot air and moisture to the attic or upper regions to the building
Allows better air flow
Maintains a healthier and more efficient environment

136
Q

What material is used as concealed flashing on roof ridges

A

Concealed valleys may use roofing felts/ water shield/metal
Hips and ridges are finished with the same shingles

137
Q

Role of roof ridges

A

Provide protective cover
Seal the junction
Prevent water from entering structure
Ventilation

138
Q

Problems of clay at ridges and tops

A

Cracking
Displacement
Damage due to weather exposure
Mortar deterioration causing gaps

139
Q

My

A
140
Q

Why is gravel not required on pvc roofs

A
141
Q

When is gravel not required for uv protection on toofs

A
142
Q

How many inches of insertion in various fladhings

A
143
Q

Why is membrane ruptured in stacks

A
144
Q

What flashings are used when wall meets dormer

A
145
Q

How to find number of layers in a closed valleys

A
146
Q

How to find number of layers in an open valley

A
147
Q

What type of condensation is seen under metal roofs

A

Water droplets or moisture build up

148
Q

What is the role of tar

A
149
Q

Which membrane is used in chimneys

A
150
Q

What are pitch pockets

A
151
Q

What are flashings used on parapet walls

A
152
Q

Where can you find wrinkling, alligator cracks

A
153
Q

What is a hem

A
154
Q

If seams are 12inches apart then how many layers

A
155
Q

What is the role of ridge flashings

A
156
Q

How much of valley flashing can you see

A

Flat roofing (2 decks)

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