Construction - Roofs

Flashcards based on lecture notes about roofing, covering topics from low-sloped and steep roofs to materials and insulation techniques.

Where should drains be placed in low sloped roofing?

At mid span between structural supports to accommodate roof deflection and prevent ponding.

What is ponding in the context of roofing?

A cycle where water accumulates on a roof, causing further deflection and more water accumulation, potentially leading to collapse.

What is the minimum slope generally allowed by code for roofs?

2%, or one quarter inch per foot, to prevent ponding.

What is an intensive green roof?

Soil is directly on the roof; flat to promote water retention.

What is an extensive green roof?

Plants are in trays that sit on top of a typical roof, requiring a minimum slope.

What is a blue roof?

Intentionally ponding water on the roof to control stormwater runoff.

Why is the roof a critical component of a building?

The roof is the horizontal span requiring more structure, is exposed to the elements, and typically needs more frequent replacement than walls.

How do you calculate the percentage of a roof slope?

Vertical distance divided by horizontal distance, multiplied by 100.

What defines a low slope roof?

Less than 2/12 (less than 17%).

What defines a steep roof?

Steeper than 2/12 (steeper than 17%).

How do you create the quarter inch slope in a low slope roof?

We can slope structure support, taper the structure beams, or taper the insulation.

What are the three families of surfaces for low slope roofs?

Bituminous sheets, rolled out plastic membranes, and sprayed-on waterproof layers.

What are substrate boards for roofing?

Gypsum or wood fiber sheets to provide a smooth surface for membrane application.

How do you account for the possibility of standing water on a roof?

Backup drains or overflow scuppers with separate piping.

What is an overflow scupper?

A system where water builds up and pours out of openings in the wall, alerting to potential drainage issues.

What are the parts of a roof drain?

Strainer, hub/sump, and a drain pipe.

What is bituminous roofing?

Based on asphalt; includes multiple layers of overlapping felt, such as built-up roofing.

What is single ply roofing?

Rolled-on plastic membrane.

What is fluid applied roofing?

Chemicals mopped or sprayed on to create a waterproof layer.

Why are bituminous roofs often covered with gravel ballast or aluminum coating?

To protect them from sunlight and reduce solar absorbance.

What is a modified bitumen roof (ModBit)?

An asphalt-based roofing with chemicals added for greater elasticity and temperature resistance.

What is an EPDM roof?

A single ply roof made of rolled-out sheets of plastic, often heat-welded or glued at the seams.

What are the most vulnerable parts of a roof for leaks?

Seams, penetrations for equipment or pipes, and differential movement from expansion/contraction.

What is a pitch pan, and why is it not ideal?

A metal pan filled with pourable sealant around a roof penetration, which is prone to leaks.

What is a cone shaped boot for roof penetrations?

A cone-shaped fitting that mechanically diverts water away from penetrations.

What is a cricket in roofing?

A mini-pitched element that diverts water around a chimney or other penetration.

What is a building separation joint in roofing?

Allows for building expansion or seismic activity with a break extending through the entire structure.

What is an expansion joint in roofing?

Allows for expansion and shrinkage of the roof membrane itself, without separating the building structure.

What is a cant strip used for?

Allows a more moderate bending of the membrane at the parapet wall.

What is counter flashing used for?

Allows for replacement of the roof membrane without removing the coping and main flashing.

What is the flashing used for?

Vapor control, preventing moisture from reaching the cold membrane.

What are topside roof vents?

Allow moisture to escape from the underside of the roof membrane.

What are the options for where we put insulation on a roof?

Below roof deck, on top of the deck but below the membrane, and on top of the membrane.

What is a vented roof?

Insulation with air moving in and out of a ventilated cavity, allowing for drying of any condensation.

What are the benefits closed cell spray foam?

Vapor barrier, air barrier, and thermal control layer without requiring venting.

What are baffles used for in a roof?

Keep insulation from blocking air movement from the soffit to the roof deck.

What is albedo?

Reflectance dealing with visible light.

What is emissivity?

Describes the heat that has been absorbed.

What materials can be used for cool roofs?

White pavers or gravel ballast to contribute to a cool roof because of their high albedo, but also because of their high emissivity.

How are the seams sealed between elements of a metal roof?

Standing seam constructed by sliding it in, nail it down, and bend it around.

What's the difference between roof shingles and roof shakes?

Roof shakes are thicker than roof shingles.

What is skip sheathing?

Using boards and we're going to nail down the boards with intentional gaps between them and that will allow the underside of the shingles to experience something a little bit warmer in the summer and a little bit cooler in the winter.

What is tangled fiber breather mat?

A mat underneath the shingles gives a surface for the shingles to attach to, but allows for air.

How to resolve roof flashings on places on vertical surfaces.

Where a vertical surface extends beyond the sloped roof we're are going to have vertical surface that extends beyond the sloped roof, we're going to have to flash.