Flat Roofing Flashcards
(156 cards)
1
Q
What is the life expectancy of built up roofing
A
10-30 years
2
Q
What are the bases for built up roofing
A
Organic felts
Asbestos,
Fibreglass
Polyester felts
3
Q
How many plies in a built up roofing
A
2-5
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
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
6
Q
What are the aggregates used for built uproofing
A
Asbestos
Marble
Rock slag
Gravel
Crushed stone
7
Q
Where is the gravel embedded
A
In the flood coat of hot asphalt.
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
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
10
Q
Do roofs covered with decks require gravel
A
No
Deck provides uv protection
Act as ballast and
Keeps roofs cooler
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
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
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
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
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
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
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
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
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
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
21
Q
How long should water be in a place to call ponding
A
48 hours
22
Q
What are the causes of ponding in flat roofs
A
Poor design
Saggin of the structure
Poor drainage
23
Q
What are the implications of ponding
A
Shorten life of membrane
Sagging of the structure
Damage to the building
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
25
What are other names for Modified bitumin
Polymer modified bitumin
MODBIT
Rubberized asphalt
26
What is the life of a MODBIT
12-20 years
27
What is the minimum slope for MODBIT
1/4 by 12
28
How many types of MODBIT are there
APP: a Atactic polypropylene
SBS: styrene Butadyne Styrene commonly called as rubberized asphalt
29
Is MODBIT asphalt compatible
Yes
30
How does MODBIT provide UV protection
Granular surface
Liquid applied latex
Foil surface: Al or copper ballast
31
How is MODBIT installed
Torced on
Mopped in with hot asphalt
Peel and stick
32
What is synthetic rubber
Commonly called synthetic rubber
This can be vulcanized or non vulcanized elastomers
33
Example of synthetic rubber
EPDM
34
Does EPDM require uv protection
No
35
What is the size of an EPDM sheet
50 ft wide
36
How is EPDM to the secured on the roof
1.contact cement or
2. Mechanically by Bars or buttons
3. Laying it loose and holding it down with ballast
37
Can EPDM be bonded with hot asphalt
No
38
Effect of oils and water from AC leaks
Roof mounted AC leak oil onto the roof damaging the EPDM
39
What flashings are used on EPDM
Epdm
40
What is the life expectancy of epdm
20 years
41
What causes tenting in EPDM
Too taught because of
shrinkage
Sheet expansion during hot whether
Insufficient allowance for membrane relaxing prior to installation
42
What is the effect of oils on EPDM roofs
Discolouration
43
What are the most common failures on EPDM roofs
Openings at the seams or flashings
44
Give examples of plastic roofing
PVC
45
What does PVC feel like
Swimming pool vinyl liners
46
Do you need gravel on pvc roofs
No
47
Is pvc compatible with asphalt
No
48
Is pvc compatible with polystyrene
No
49
How is pvc secured to the roof deck
Contact cement
Mechanical fasteners
Securement strips
50
What is the size and thickness of pvc
5-10 ft wide
69-100 ft wide thickness 0.8mmyo 1.5 mm
51
What are the flashings for pvc roofs
Upvc or pvc clad metal
52
Should you walk on pvc roofs
No if temp is 10 degree c
53
Is pvc effected by air pollution or uv radiation
Yes
54
Life of pvc
20 years
55
What is the life of roll roofing
5 years
56
What is another name for roll roofing
Selvage
57
Do flat roofs shed water
Like all roofs there has to be a slight slope
58
In concealed fasteners is it better to use nails or screws
Screws are better
59
Function of base and counter flashing
They make the transition from the membrane to the adjoining material ie mask art wall or metal stack
60
What is a can't strip
Triangular blocks of wood that allows a 90 degree turn to 2 45 degree turn s as membrane goes up the wall
61
How is it a good idea to use a can't strip
Less cracking at the change in direction
62
what is a base flashing, where is it located ho.
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.
63
Is base flashing secured to the wall,
No
64
What materials are base flashings made up of
Roofing felts
Fabric reinforced asphalt products
Modifies bitumens
Synthetic rubber ie neopreneplastics
Various modifications of the above
65
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
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
How is the gravel stop secured to the roof and wall?
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
How is the metal drip edge flashing sealed after nailing or screwing.
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
How is a metal edge flashing installed on a ePDM or modbit ie single ply instead inorganic felt
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
How else do roofs end
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
What flashings are used when a flat roof meets with a wall
Base flashing and counter flashing
71
What's a can't strip
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
What's the base flashing
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
What is the counter flashing when a flat roof meets a wall
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
What's another counter flashing
A two piece counter flashing.
The top part is permanently set into the wall and the other is removable
75
What's a hem
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
Do roofs and walls move
They do and can pull apart the best installed flashing details
77
What is the elegant solution to prevent damage due to roof wall movement
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
What if the roofing is MODBIT pvc or epdm
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
What are coping's in parapet walls
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
Does the parapet wall drain inside or outside
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
What flashings are used on chimneys
Base and counter flashing
82
How much should a chimney cap extend above the chimney face
1 inch
83
On a flat roof what should be the height of the curb for a skylight
8 inches
84
What is a pitch pan or pitch pocket in stacks
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
How are internal drains connected to a pipe
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
Where are scuppers installed
Primary scupper at the elevation of the membrane and secondary scuppers 2 inches above
87
If Flat roof draining into sloped roof what steps are taken to prevent leakage
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
What if it's the opposite- ie steep roof that drains onto flat roof below
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
3. 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
What conditions cause flashings being pulled away by membrane
Cooling in epdm and pvc due to shrinkage
90
Which words mean the same
Mastic is roofing
Cement is asphalt
Cement is plastic cement
All are applied with a trowel
91
Why do leaks show up some distance in the interiors from the failure point
Water May travel horizontally along plastic vapour barriers before coming through the ceiling
92
What is the life expectancy of Built up roofing
10 years
93
What is the life expectancy of roll roofing
5 years
94
What is the life expectancy of MODBIT
12-20 years
95
What is the life expectancy of clay tiles
100 years
96
What is the life expectancy of neoprene flashing
10-20 years
97
What is the life expectancy of lead flashings
30 years
98
What is the life expectancy of epdm
20 years
99
What is pvc not compatible with
Asphalt
100
What is epdm not compatible either
Asphalt
101
If adjacent chimney wall is made of asphalt then how to secure it
By securing a reglet
102
How many types of flashings can u find on chimneys
Three
Side top
Bottom
103
What causes effervescence at base of chimneys
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
Do we describe roofs
no we only inspect them
105
With what material is TPO is incompatible with
Like EPDM and pvc - TPO is incompatible with asphalt
106
Which sidings act as a counter flashing to keep material from rotting
Wood
Aluminum
Vinyl
Stucco
107
Why does leakage in a roof see a distance away from the point of leakage
Plastic water vapour travels some distance before condensation
108
What is copings
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
What is a bar clamp
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
What are the causes of roof sagging
Excess weight of material ie asphalt or station or debris
Weight of snow
Water ponding
111
How is a curved tile flashed
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
How much should the base cap of the chimney flashing should go into the roof
4-12 inches
113
What are up stands
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
Are exposed nails used in valleys
Never
115
Which sides wear off fast
South and west due to uv rays
116
Which is the best Eve protection in order of priority
1.Mod bit
2 .metal sheathing
3.Polyethylene
4.roof felts
5.roll roofing
117
At what distance are fasteners used to secure membrane on built up roofing's
12 inches apart with 2 nails close every three inches
118
Where are avalanche guards commonly found
Slate
Clay
Concrete
119
When are sidings used as counter flashing to keep wood from rotting or soaking
Wood
Al
Vinyl
Stucco
120
Role of ridges
Protection
Venting
121
Other name for netal
Galal me
Galvanized steel
Zinc
Copper
Terne
Tin
122
Other name for single ply roof
PVC
MODBIT
Poll roofing
123
How is counter flashing secured to a mortar wall
Metal bent at the end and end is secured through mortar as a reglet.
124
What are the problems of clay tiles at ridges
125
What is pvc not comparability with
Asphalt
126
What is Al not comparability with
Mortar
127
How are skylights sealed
Hermetically or vented
128
What material is used in solariums
Glass
Wood
Metal
129
Where is the maximum problems in solariums
First wall solarum interface
Then joints with glass
Then kitchen
Then glass tops
130
After valley flashing where is the other leakage
Penetration
Then slash points
Then roof joints and then skylights
131
If condensation is more uniform and widespread then what is it due to
It's a winter problem only
132
If the condensation is concentrated then what's the cause
Due to rain
133
What flashings are used in dormers
Step flashing on sides
Cap flashing on top
Base flashing on botyom
134
Which roofs have cap flashings
Asphalt and metal roofs have ridge caps or hip caps
135
Role of ridges in venting
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
What material is used as concealed flashing on roof ridges
Concealed valleys may use roofing felts/ water shield/metal
Hips and ridges are finished with the same shingles
137
Role of roof ridges
Provide protective cover
Seal the junction
Prevent water from entering structure
Ventilation
138
Problems of clay at ridges and tops
Cracking
Displacement
Damage due to weather exposure
Mortar deterioration causing gaps
139
My
140
Why is gravel not required on pvc roofs
141
When is gravel not required for uv protection on toofs
142
How many inches of insertion in various fladhings
143
Why is membrane ruptured in stacks
144
What flashings are used when wall meets dormer
145
How to find number of layers in a closed valleys
146
How to find number of layers in an open valley
147
What type of condensation is seen under metal roofs
Water droplets or moisture build up
148
What is the role of tar
149
Which membrane is used in chimneys
150
What are pitch pockets
151
What are flashings used on parapet walls
152
Where can you find wrinkling, alligator cracks
153
What is a hem
154
If seams are 12inches apart then how many layers
155
What is the role of ridge flashings
156
How much of valley flashing can you see
