R,S,

Dictionary of Roofing Terms

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R-Value: The measure of a material’s resistance to heat flow. The higher a material’s R-value, the more it insulates. For more information on R-Value, See Table 1

Racking: The method of installing asphalt shingles where the shingles are installed straight up to the ridge rather than horizontally. If this method is used with 3-tab shingles, the throats of every other course will line up.

Rafter: The structural member extending from the downslope perimeter of a roof to the ridge or hip and is designed to support the roof deck and roof system components.

Raggle: A groove that is cut into the side of a vertical surface such as a wall or chimney that is used to insert a flashing element such as a reglet or counterflashing.

The red arrow in the following image shows a Raggle. The greyish pieces that you see are pieces of lead being used to hold the flashings in place until they can be properly mortared.

Raggle

Rake: The sloped perimeter edge of a roof that runs from the eaves to the ridge. The rake is usually perpendicular to the eaves and ridge. (See Fig 1)

Rake-Starter: A starter strip placed along rake edges for use in asphalt shingle roofing. See also Bleeder Strip.

Re-Cover (Overlay): The installation of a new roof system over an existing system without removing an existing system

Reinforced Membrane: A roofing membrane that has been strengthened by adding polyester scrims or mats, glass fibres or other material.

Relative Humidity: The amount of water vapour in the air compared to the amount of water vapour that the air can hold at a given temperature. For example, if the relative humidity is 50 percent, then the amount of water vapour in the air is half of what the air could actually hold at that temperature.

Re-roofing: The procedure of installing a new roof system.

Ridge: The line where two planes of roof intersect, forming the highest point on the roof that runs the entire length of the roof. (See Fig 1)

Ridge Cap: Material applied over the ridge or hip of a roof.

Ridge Course: The final course of roofing applied that covers the area where two or more roof planes intersect.

Ridge Vent: An exhaust venting device located at the ridge of a roof that works in conjunction with a starter or under eave soffit vent and is used to ventilate attics. Ridge vents and their cooperative starter or soffit vents should be installed at a 1:1 ratio in order to function properly.

Ridging: The formation of a Buckle.

Roll Goods: The term used for all roofing materials that come in rolls.

Roof Assembly: A term used to describe all of the roof components including structural roof deck.

Roof boards: (Sarking in Scotland) Boards fixed to the rafters to provide a fixing and undercovering for the covering materials proper, eg. slates, tiles

Roof Curb: A frame used to structurally mount rooftop equipment such as HVAC units, exhaust fans, skylight, etc.; may be pre-constructed or constructed on site.

Roofer: An individual who installs roof systems and materials.

Roof Jack: (1) A steel bracket fastened to the roof that is used to support toe boards. (2) A term used to describe a Pipe Boot or Flashing Collar.

Roof Overhang: That portion of the roof that extends beyond the exterior wall line of the building.

Roof Seamer: (1) A mechanical device used to crimp metal roof panels and make the seams watertight. (2) A machine used to weld membrane laps of PVC (Thermoplastic) roofing material.

Roof Slope: The angle made by the roof surface plane with the horizontal plane and expressed as the amount of vertical rise for every twelve inch (12") horizontal run. For instance, a roof that rises four inches (4") for every twelve inch (12") horizontal run, is expressed as having a "four in twelve" slope; often written as "4:12." Expressed as a percentage, the slope would be 33%, which is equal to 4 divided by 12. Also known as the Pitch of a roof. For more information on Roof Slope, See Fig 2

Roof System: Multiple roof components assembled to provide waterproofing (and sometimes insulating) capabilities for a structure.

Run: The horizontal dimension of a slope. See Fig 2.

Rust Blush: Early stage of rust indicated by an orange or reddish colour.

Saddle: (1) A type of flashing usually used in conjunction with step, counter, and apron flashings on steep slope roof systems. (2) A small, somewhat pyramid-shaped figure constructed in between sump drains that is used to direct run-off water toward the sump drains.

Sag: Settling or drooping of base flashings that have not been properly secured to a surface or boards due to moisture exposure.

Sarking: See roof boards

Scrim: Woven or nonwoven material used to reinforce membranes; it is usually laminated or coated to produce the membrane.

Scuttle: A unit that provides access to the roof from the interior of the building. See also Hatch.

Sealant: Generic term for a multitude of materials used to seal joints or junctures against moisture or weather.

Sealer: Coating designed to prevent bleed-out or bleed-through.

Self Levelling: A term used to describe a viscous material that is applied by pouring, in its uncured state, it spreads out evenly.

Selvage: The unsurfaced strip along a sheet of roll roofing which forms the under portion at the lap in the application of the roof covering.

Shed Roof: A roof having only one slope or pitch, with only one set of rafters which fall from higher to lower wall.

Shingles: Small units of material which are laid in a series of overlapping rows as a covering on pitched roofs.

Shop drawing: A drawing prepared by the fabricator based on a working drawing and used in a
shop or on a site for assembly

Silicone Sealant: A sealant having as its chemical compound a backbone consisting of alternate silicone-oxygen atoms. Low Modulus Silicones are usually appropriate for sealing joints liable to substantial moisture or thermal movement, and, if acetoxy silicones, are very fast curing, durable, thick bodied and particularly suited to UPVc glazing and light construction uses.
High Modulus Silicones are usually extremely durable and weathertight, providing good performance on many general applications; they have a 5 minutes skin formation time and are for interior and exterior use and, if acetoxy silicones, are flexible and suitable for glass, aluminium, painted surfaces, ceramics and non-porous surfaces.

Skew: Method of putting in nails in at a slight angle, one opposing the next so as to greatly decrease the chance of the boards lifting.

Skylight: A structure on the roof that is designed to admit light and is somewhat above the plane of the roof surface.

Slate: A dark grey stratified stone cut relatively thin and installed on pitch roofs in a series of overlapping rows.

Slitting: (Metal sheeting) A process by which wide sheet is slit or cut into narrower widths.

Slope: Incline or pitch of roof surface.

Soffit: The underside of a part or member of a building extending out from the plane of the buildings walls.

Span: The horizontal distance between supporting structures such as beams, trusses, or columns.

Specification: Detailed written instructions which, when clear and concise, explain each phase of work to be done.

Stack: The vertical pipe of a system of soil, waste or vent piping.

String Line: A nylon lide usually strung tightly between two supports to indicate direction and elevation.

Subgirt: Heavy duty metal strips used to support facades, mansards, etc.

Substrate: A part or substance which lies below and supports another.

Although these pages are checked regularly and every care is taken with the information within. Delston can not accept any responsibility or liability for information or results displayed within due to third party interference.

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