Roofs Flashcards

1
Q

What requirements might you consider when designing a roof?

A

Ventilation

Insulation

Structural integrity

Resistance to moisture

Wind loading

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2
Q

What are key considerations when designing flat roofs?

A

Dead and imposed loads

Prevention of water penetration

Heat retention but also interstitial condensation

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3
Q

What is a cold roof?

A

A roof where the insulation on the underside of the structural deck.

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4
Q

What is a warm roof?

A

A roof where the insulation is on top of the structural deck, sandwiched between the vapour control layer and waterproof covering.

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5
Q

What is an inverted roof?

A

A roof where the insulation sits on top of both the structural deck and waterproof covering and it typically held down by ballast.

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6
Q

What is the typically frequency of wall straps?

A

2M centres

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7
Q

When is a vapour control layer required?

A

Where no ventilation is allowed within the roof then a VCL is needed.

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8
Q

What is the purpose of a vapour control layer?

A

To prevent warm damp meeting the dew point in the roof and causing interstitial condensation.

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9
Q

Under part L, what U-value does a falt roof need to reach as a minimum?

A

0.18

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10
Q

What are different types of flat roof covering you might specify?

A

Asphalt

GRP

Built up felt

Single ply such as EPDM

Lead

Zink

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11
Q

Why might your specify Asphalt and what are some of the disadvantages?

A

Cost-effective and has a 25 year life expectancy

Heat applied in bays and then covered in a layer of UV paint

Pros: seamless

Cons: prone to embrittlement and slumping at upstands.

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12
Q

Why might your specify GRP and what are some of the disadvantages?

A

Cold applied and can therefore be installed without hot works permits. It is suitable for use an an overlay system.

Pros: jointless and lightweight

Cons: weather dependent install and relatively costly.

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13
Q

Why might your specify a felt system and what are some of the disadvantages?

A

layers of felt laid a right angles with cap sheet for UV protection - 25 year life expectancy

Typically torched on

Pros: straightforward installation

Cons: trapped moisture can result in blistering requiring careful detailing.

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14
Q

Why might your specify a single ply system and what are some of the disadvantages?

A

EPDM - life expectancy of 25 years

Pros: lightweight

Cons: due to complex detailing required it is more likely to fail due to poor workmanship. The detailing can also therefore be time consuming.

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15
Q

What solar protection options are there for flat roof systems?

A

stone chippings

paving slabs

solar reflective paint

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16
Q

What does the code of lead refer to?

A

The thickness and weight of the lead.

17
Q

What should you consider when specifying lead?

A

Whether the building is listed

The exposure of the area

The type of application e.g flat roofing, parapet gutter, flashings.

Requirements for life expectancy and durability

The requirement for thermal movement

18
Q

What is the British standard for lead?

A

BSEN 12588:2006 Rolled Lead Sheet for Building Purposes