EXTERIOR FINISHES

What are the main components commonly found in a roof assembly?

Structural framing (rafters or trusses), roof sheathing, underlayment or roofing felt, roofing finish (such as shingles or standing-seam metal), flashing/drip edge, ventilation components, insulation, and air sealing

What is roof sheathing?

The panel layer installed over roof framing that provides a continuous base for underlayment and roofing

What are the two common types of roof framing?

Rafters and trusses

What is roofing felt used for?

It is an underlayment layer that helps dry in the building and provides secondary protection beneath the roofing material

What are advantages of synthetic roofing underlayment?

It is lighter, more tear-resistant, and less sensitive to sunlight exposure than traditional felt, but it costs more

What is the basic rule for lapping water-shedding materials?

Install each upper layer over the layer below it so water drains outward and downward rather than behind the material

Which materials are commonly installed with laps?

Roofing felt, housewrap, and shingles.

What is a drip edge?

A bent sheet-metal edge that directs water away from trim and siding so it can drip free of the building

What is the purpose of attic ventilation?

It allows air to circulate below the roof sheathing, helping manage heat and moisture and keeping the sheathing cooler in cold conditions

Where are roof ventilation openings commonly located?

At eaves, and in ventilated roof systems also at eaves and rakes

What causes an ice dam?

Heat escaping from below melts snow higher on the roof; the water reaches the colder eave, refreezes, and builds up as ice

Why are ice dams a problem?

Meltwater can back up behind the ice and seep beneath shingles and through the roof sheathing

How can ice dams be reduced?

Keep roof sheathing cold with ventilation, provide adequate insulation, and air-seal to limit warm air entering the attic

What is an ice-and-water shield?

A code-required waterproof roof membrane used to protect vulnerable roof areas from water backup; it must extend at least 24 inches over the insulated portion of conditioned space

How is roof drainage achieved?

Roof slope sheds water to gutters; gutters slope toward downspouts, also called rain leaders, which carry water away

What factors determine gutter size?

Local rainfall intensity, roof design area, and the linear feet of gutter serving the roof

Why are roof overhangs important?

They protect walls from weather by reducing the amount of rain that reaches the building façade

What is a weather-resistive barrier (WRB)?

A water-control layer behind exterior cladding that helps prevent water from reaching vulnerable wall materials while allowing the wall assembly to manage moisture.

How is a mechanically fastened WRB installed?

In overlapping layers, installed from bottom to top so upper layers lap over lower layers

What is an integrated WRB?

A WRB built into the sheathing panel, such as OSB with an integral barrier. Joints are sealed with tape instead of lapped sheet layers

What is a benefit of integrated WRB sheathing?

Installing the sheathing also installs the WRB, which helps dry in the building during construction

Where are fluid-applied WRBs most common?

Commercial construction

What is a rainscreen assembly?

A wall assembly with cladding separated from the WRB by an airspace. The cavity permits drainage and helps ventilate and dry the wall

What are the key parts of a rainscreen assembly?

Sheathing, an air/moisture barrier or WRB, furring or spacers, an air cavity, insect screening at openings, and exterior cladding

Why is insect screening used in a rainscreen cavity?

It keeps insects out while allowing air movement and drainage

How does rainscreen furring change for vertical wood siding?

Vertical spacers create a vertical drainage cavity directly behind the vertical siding

How does rainscreen furring change for fiber-cement lap siding?

Vertical furring creates the drainage plane behind the horizontal lap siding

Why can horizontal furring be added behind vertical wood siding?

It provides fastening support for the vertical cladding, while a separate vertical furring layer maintains a continuous drainage path

What is the main rainscreen rule when selecting furring orientation?

Preserve a continuous vertical drainage and ventilation path behind the cladding; do not block it with horizontal furring alone

What is the overall water-management principle for roofs and rainscreens?

se gravity and layered materials to shed water outward, provide drainage paths for water that gets behind the exterior surface, and ventilate cavities so assemblies can dry

What is the overall idea of Exterior finishes?

Top layers lap over bottom layers; water moves down and out