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Dictionary of Roofing Terms
If you would like to add a term to the list please feel free to e-mail us by clicking on the link above and we will add it for you.
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O Open Valley: A valley where both sides of the roof are trimmed back from the centreline to expose the valley flashing material beneath. Orange Peel Surface Texture: A surface with a texture comparable to the skin of an orange upon which a protective coating may be applied. Organic: Formed from hydrocarbons. OSB: Oriented Strand Board - Often used as roof sheathing in place of plywood and predominantly used in the flat roof industry instead of plywood and chipboard.
This is a photograph of what OSB (Oriented Strand Board) looks like. It is often used in place of plywood for roof sheathing. Overlay: See Re-Cover. Overspray: The loss of spray particles (from coatings, SPF, etc.) in the air. P Pallet: A platform used to hold materials. Pan: (1) The concave piece of "Pan and Cover" tile whose rounded surface touches the top side of the roof substrate. (2) The flat part of a roofing panel located between the ribs. Pan Flashing: A sheet metal flashing that covers an equipment platform and is designed to counter flash the base flashings surrounding the platform. Parapet Wall: That part of a perimeter wall that extends above the surface of the roof. Pass: The term used to describe the application of one layer of Spray Polyurethane Foam (SPF). The speed of a pass will determine foam thickness. Pass Line: The distinct line formed between two passes of SPF. This line is the top skin of the bottom pass of the SPF. Peggies: Slates 10-14in (254-356mm)in length. Penetration: Any object that pierces the surface of the roof. Percent Elongation: The maximum amount that a material can be lengthened or stretched before breaking; expressed as a percentage of the original length of material tested. Perlite: A natural volcanic glass having distinctive concentric cracks and a relatively high water content. Perlite in a fluffy heat expanded form is used in lightweight insulating concrete, fire-resistant rigid insulation board (R = 2.78 per inch) and potting soil. Perm: A unit of water vapour transmission, defined as one grain of water vapour per square foot per hour per inch of mercury (Hg) pressure difference (1 inch of mercury = 0.491 psi).Permeability: The rate of flow of a liquid or gas through a porous material. PH: A measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14. Phasing: Installing roof system components in separate time intervals. For instance, installing a base sheet, and then two plies of roofing one day, and coming back and installing the remaining two plies one or more days later. It is generally not considered Phasing if the surfacing is applied at a later date. Pinhole: A small hole in a coating, foil, membrane, or other roofing material. Pipe Boot: A prefabricated flashing piece used to flash around circular pipe penetrations. Also known as a Roof Jack. Pitch: Term used to describe Roof Slope and also short for Coal Tar Pitch. Pitch Pocket (A.K.A. Pitch Pan): A flanged piece of flashing material placed around irregularly shaped roof penetrations and filled with grout and a pourable sealer to seal around the penetration in order to seal it from against moisture entry. Pitch pockets are a good source of leaks and should be avoided if possible. For an example on how to properly fill a pitch pocket,
Plywood: Wooden panels formed by gluing thin sheets of wood together, with the grain of adjacent layers arranged at right angles. Polymer: Any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule. Polyvinyl Chloride (PVC): A thermoplastic polymer that can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers, and other modifiers; rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and roof membrane materials. Ponding: The accumulation of water at low-lying areas on a roof. Pop Rivet: A small metal pin having a head on one end, inserted through aligned holes in pieces of light gauge metal to be joined and then the head is expanded to join the metal. Popcorn Surface Texture: A coarse surface texture of SPF considered unacceptable for coatings. Positive Drainage: The drainage condition of a roof where all water is gone from the roof surface within forty-eight hours of precipitation during normal drying conditions. Pot Life: The period of time during which a material with multiple ingredients can be applied or administered after being mixed together. Pourable Sealer: A type of sealant that is initially in liquid form commonly used in conjunction with pitch pans to form a watertight barrier around penetrations that are difficult to flash. Primer: A material that is applied to a surface in order to increase that surface’s ability to adhere to or work in conjunction with a subsequently applied material. Proportioner: A pumping unit comprised of two (2) positive displacement pumps that is designed to dispense two (2) components at a precise ratio. Used in SPF and plural component coating applications. Puncture Resistance: The ability of a material to withstand being pierced by a sharp object. Purlin: Horizontal secondary structural member used to transfer loads from the primary structural members. PVC: Polyvinyl Chloride.
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. Author Myrddin
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