Roofing Terms D – F
- -D-
- Dampproofing
- treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.
- Dead level
- absolutely horizontal or zero slope. (see Slope.)
- Dead-level asphalt
- see Asphalt.
- Dead loads
- the weight of a structure itself, including the weight of fixtures or equipment permanently attached to it.
- Deck
- a structural component of the roof of a building. The deck must be capable of safely supporting the design dead and live loads, including the weight of the roof systems, and the additional live loads required by the governing building codes and provide the substrate to which the roofing or waterproofing system is applied the structural surface of a building to which a roof assembly is installed. Decks are either non-combustible (e.g., corrugated metal, concrete, or gypsum) or combustible (e.g., wood plank or plywood).
- Deflection (bowing, sagging)
- (1) the deformation of a structural member as a result of loads acting on it; (2) any displacement in a body from its static position, or from an established direction or plane, as a result of forces acting on the body.
- Degradation
- a deleterious change in the chemical structure, physical properties or appearance of a material from natural or artificial exposure (e.g., exposure to radiation, moisture, heat, freezing, wind, ozone, oxygen, etc.).
- Degree days
- a unit used in estimating the fuel consumption for a building; equal to the number of degrees that the mean temperature, for a 24-hour day, is below the “base temperature”; the base temperature is taken as 65° F (18.3° C) in the U.S.A.
- Delamination
- separation of the laminated layers of a component or system.
- Design loads
- the total load on a structural system for the most severe combination of loads and forces which it is designed to sustain.
- Dew-point temperature
- the temperature at which air becomes saturated with water vapor. The temperature at which air has a relative humidity of 100%.
- Diaphragm
- a floor slab, metal wall panel, roof panel, or the like, having a sufficiently large in-plane shear stiffness and sufficient strength to transmit horizontal forces to resisting systems.
- Diffusion
- the movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration.
- Dimensional shingle
- a shingle that is textured, overlayed, or laminated and designed to produce a three-dimensional effect. (see Laminated Shingle and Architectural Shingle.)
- Dimensional stability
- the degree to which a material maintains its original dimensions when subjected to changes in temperature and humidity.
- DOE
- U.S. Department of Energy.
- Dormer
- a structure projecting from a sloping roof usually housing a window or ventilating louver.
- Double coverage
- application of asphalt, slate, or wood roofing such that the lapped portion is at least 2 inches (50 mm) wider than the exposed portion, resulting in two layers of roofing material over the deck.
- Double lock standing seam
- in a metal roof panel or metal cap, a standing seam that uses a double overlapping interlock between two metal panels. (see Standing Seam.) The NRCA Roofing and Waterproofing Manual—Fifth Edition 982 Glossary
- Double pour
- to apply two layers or flood coats of bitumen and aggregate to a built-up roof.
- Downspout
- a vertical pipe or conduit used to carry runoff water from a scupper, conductor head or gutter of a building to a lower roof level or to the ground or storm water runoff system.
- Drag load
- the external force (e.g., from the weight of ice and snow) applied to a steep-slope roof system component forcing the component downslope.
- Drain
- an outlet or other device used to collect and direct the flow of runoff water from a roof area.
- Drip edge
- a metal flashing or other overhanging component with an outward projecting lower edge, intended to control the direction of dripping water and help protect underlying building components.
- Dry
- free or relatively free from a liquid, especially water; (2) to remove water or moisture.
- Dry bulb temperature
- the temperature of air as measured by an ordinary thermometer.
- Dry film thickness
- the thickness, expressed in mils, of an applied and cured coating or mastic. For comparison, see Wet Film Thickness.
- Drying time
- the time required for the loss of volatile components so that the material will no longer be adversely affected by weather conditions such as dew, rain, or freezing.
- Dual level drain
- in waterproofing, an outlet or other device with provisions for drainage at both the wearing surface and waterproofing membrane levels used to collect and direct the flow of runoff water from a horizontal slab.
- Dynamic load
- any load which is nonstatic, such as a wind load or moving live load.
- Top of Page
- -E-
- Eave
- the lower edge of a sloping roof that part of a roof which projects beyond the wall.
- Eave height
- the vertical dimension from finished grade to the eave.
- Eave-trough
- see Gutter.
- ECH
- polyepichlorohydrin, commonly referred to as epichlorohydrin. (see Epichlorohydrin.)
- Edge stripping
- membrane flashing strips cut to specific widths used to seal/flash perimeter edge metal and the roof membrane application of felt strips cut to narrower widths than the normal felt-roll width to cover a joint between metal perimeter flashing and built-up roofing.
- Edge venting
- the practice of providing regularly spaced or continuously protected (e.g., louvered) openings along a roof edge or perimeter, used as part of a ventilation system to dissipate heat and moisture vapor.
- Efflorescence
- an encrustation of soluble salts, commonly white, deposited on the surface of stone, brick, plaster, or mortar; usually caused by free alkalies leached from mortar or adjacent concrete as moisture moves through it.
- EIP
- ethylene interpolymer.
- Elasticity
- the property of a body that causes it to tend to return to its original shape after deformation (as stretching, compression or torsion).
- Elastomer
- a macromolecular material that returns rapidly to its approximate initial dimensions and shape after substantial deformation by a weak stress and subsequent release of that stress.
- Elastomeric coating
- a coating that is capable of being stretched at least twice its original length (100 percent elongation) and recovering to its original dimensions.
- Elongation
- the ratio of the extension of a material to the length of the material prior to stretching. The NRCA Roofing and Waterproofing Manual—Fifth Edition Glossary 983
- Embedment
- (1) the process of pressing/positioning a felt, aggregate, fabric, mat, or panel into hot bitumen or adhesive to ensure intimate contact at all points; (2) the process of pressing/positioning granules into coating in the manufacture of factory-prepared roofing, such as shingles.
- Embrittlement
- the loss of flexibility or elasticity of a material.
- Emulsion
- A mixture of bitumen and water, with uniform dispersion of the bitumen or water globules, usually stabilized by an emulsifying agent or system.
- End lap
- the distance of overlap where one ply, pane, or piece extends beyond the end of the immediately adjacent underlying ply, panel, or piece.
- Envelope (Bitumen-stop)
- a continuous membrane edge seal formed at the perimeter and at penetrations by folding the base sheet or ply over the plies above and securing it to the top of the membrane. The envelope prevents bitumen seepage from the edge of the membrane.
- EPDM
- Ethylene propylene diene monomer (see Ethylene Propylene Diene Terpolymer.)
- Epichlorohydrin (ECH)
- a synthetic rubber including two epichlorohydrin based elastomers. It is similar to and compatible with EPDM.
- Epoxy
- a class of synthetic, thermosetting resins that produce tough, hard, chemical-resistant coatings and adhesives.
- Equilibrium moisture content (EMC)
- (1) the moisture content of a material stabilized at a given temperature and relative humidity, expressed as percent moisture by weight.
- Equiviscous temperature (EVT)
- the temperature at which a bitumen attains the proper viscosity for built-up membrane application.
- Equiviscous temperature (EVT) application range
- the recommended bitumen application temperature range. The range is approximately 25° F (14° C) above or below the EVT, thus giving a range of approximately 50° F (28° C). The EVT range temperature is measured in the mop cart or mechanical spreader just prior to application of the bitumen to the substrate.
- Equiviscous temperature (EVT) for asphalt
- the recommended EVT for roofing asphalt (ASTM D 312, Type I, II, III or IV) is as follows
- Mop application
- the temperature at which the asphalt’s apparent viscosity is 125 centipoise (0.125 Pa•s).
- Mechanical spreader application
- the temperature at which the asphalt’s apparent viscosity is 75 centipoise (0.075 Pa•s). Note: In order to avoid the use of two kettles if there are simultaneous mop and mechanical spreader applications, the EVT for mechanical spreader application can be used for both application techniques.
- Equiviscous temperature (EVT) for coal tar
- the recommended EVT for roofing coal tar (ASTM D 450, Type I or III) is the temperature at which the coal tar’s apparent viscosity is 25 centipoise (0.025 Pa•s).
- Ethylene interpolymers (EIP)
- a group of thermoplastic compounds generally based on PVC polymers from which certain single-ply roofing membranes can be formulated.
- Ethylene propylene diene terpolymer (EPDM)
- designated nomenclature of ASTM for a terpolymer of ethylene, propylene and diene. EPDM material is a thermosetting synthetic elastomer.
- EVT
- Equiviscous temperature.
- Exhaust ventilation
- air that is vented or exhausted from the roof cavity, typically through vents installed on the up slope portion of the roof. For example, with most steep-slope roof assemblies, exhaust vents are typically located at or near the ridge. The NRCA Roofing and Waterproofing Manual—Fifth Edition 984 Glossary
- Exotherm
- heat generated by a chemical reaction.
- Expansion cleat
- a cleat designed to accommodate thermal movement of metal roof panels.
- Expansion joint
- a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.
- Exposed-nail method
- a method of asphalt roll roofing application in which all nails are driven into the adhered, overlapping course of roofing. Nails are exposed to the weather.
- Exposure
- (1) the traverse dimension of a roofing element or component not overlapped by an adjacent element or component in a roof covering. For example, the exposure of any ply in a built-up roof membrane may be computed by dividing the felt width, minus 2 inches (51 mm), by the number of shingled plies; thus, the exposure of 36 inch (914 mm) wide felt in a shingled, four-ply membrane should be approximately 81/2 inches (216 mm) (See Figure 8); (2) the dimension of sidewall or roofing covering that is not covered or overlapped by the up slope course of component. The typical exposure for a standard-sized, three-tab shingle is 5 inches (127 mm), depending on manufacturer specifications.
- Extrusion
- a process in which heated or unheated material is forced through a shaping orifice (a die) in one continuously formed shape, as in film, sheet, rod or tubing.
- Eyebrow
- a dormer, usually of small size, whose roof line over the upright face is typically an arched curve, turning into a reverse curve to meet the horizontal at either end. Also, a small shed roof projecting from the gable end of the larger, main roof area.
- Top of Page
- -F-
- Fabric
- a woven cloth or material of organic or inorganic filaments, threads, or yarns used for reinforcement in certain membranes and flashings.
- Factory Mutual Research (FMR)
- commonly referred to as “FM,” a research and testing organization that classifies roofing components and assemblies for their fire, traffic, impact (hail), weathering, and wind-uplift resistance for four major insurance companies in the United States.
- Factory seam
- a splice/seam made by the manufacturer during the assembly of sections of materials into larger sheets/panels.
- Fading
- any lightening of initial color.
- Fallback
- a reduction in bitumen softening point, sometimes caused by refluxing or overheating in a relatively closed container. (see Softening Point Drift.)
- Fascia
- (1) in steep-slope roofing, a board that is nailed to the ends of a roof rafter; sometimes supports a gutter; (2) in low-slope roofing, the vertical or steeply sloped roof or trim located at the perimeter of a building. Typically, it is a border for the low-slope roof system.
- Fastener
- any of a wide variety of mechanical securement devices and assemblies, including nails, staples, screws, cleats, clips and bolts, which may be used to secure various components of a roof assembly.
- Feathering strips
- tapered wood filler strips placed along the butt ends of old wood shingles to create a relatively smooth surface when reroofing over existing wood shingle roofs. Referred to in some regions of the country as “horse feathers,” or leveling strips.
- Felt
- a flexible sheet manufactured by the interlocking of fibers with a binder or through a combination of mechanical work, moisture and heat. Felts are manufactured principally from wood pulp and vegetable fibers (organic felts), asbestos fibers (asbestos felts), glass fibers (glass fiber felts or ply sheets), or polyester fibers.
- Felt machine (Felt Layer)
- a mechanical device used for applying bitumen and roofing felt or ply sheet simultaneously.
- Ferrule
- a metal sleeve placed inside a gutter at the top. A spike or screw is nailed/screwed through the gutter face and ferrule into the fascia board to hold the gutter in place. The ferrule acts as a spacer in the gutter to maintain its original shape. The NRCA Roofing and Waterproofing Manual—Fifth Edition Glossary 985
- Field seam
- a splice or seam made in the field (not factory) where overlapping sheets are joined together using an adhesive, splicing tape, or heat- or solvent-welding.
- Filler
- a relatively inert ingredient added to modify physical characteristics.
- Fillet
- a heavy bead of waterproofing compound or sealant material generally installed at the point where vertical and horizontal surfaces meet; to reduce the desired effect to take out the 90° angle at the base of a vertical flashing.
- Film
- sheeting having a nominal thickness not greater than 10 mils (0.25 mm).
- Film thickness
- the thickness of a membrane or coating. Wet film thickness is the thickness of a coating as applied; dry film thickness is the thickness after curing. Film thickness is usually expressed in mils (thousandths of an inch).
- Fin
- a term used to describe a deck surface condition. A sharp raised edge (generally in concrete) capable of damaging a roof membrane or vapor retarder.
- Fine mineral-surfacing
- water-insoluble, inorganic material, more than 50 percent of which passes through a No. 35 sieve. Used on the surface of various roofing materials and membranes to prevent sticking.
- Fire resistance
- the property of a material or assembly to withstand fire or give protection from it.
- Fire retardant treated (FRT) plywood
- plywood which has been impregnated, under pressure, with mineral salts; in the event of fire, the burning wood and salts emit noncombustible gases and water vapor instead of the usual flammable vapors.
- Fishmouth
- (also referred to as an edge wrinkle) (1) a half-cylindrical or half-conical shaped opening or void in a lapped edge or seam, usually caused by wrinkling or shifting of ply sheets during installation; (2) in shingles, a halfconical opening formed at a cut edge.
- Flaking
- in protective coatings, the detachment of small pieces of the coating film.
- Flammable
- subject to easy ignition and rapid flaming combustion.
- Flame retardant
- a chemical used to impart flame resistance.
- Flame spread
- the propagation of a flame away from its source of ignition.
- Flammability
- those characteristics of a material that pertain to its relative ease of ignition and ability to sustain combustion.
- Flange
- the projecting edge of a rigid or semi-rigid component, such as a metal edge flashing flange.
- Flash point
- the lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to a flame.
- Flashing
- components used to weatherproof or seal roof system edges at perimeters, penetrations, walls, expansion joints, valley, drains and other places where the roof covering is interrupted or terminated. For example, membrane base flashing covers the edge of the field membrane, and cap flashings or counterflashings shield the upper edges of the base flashing.
- Flashing cement
- a trowelable mixture of solvent-based bitumen and mineral stabilizers that may include asbestos or other inorganic or organic fibers. Generally, flashing cement is characterized as vertical-grade, which indicates it is intended for use on vertical surfaces. (see Asphalt Roof Cement and Plastic Cement.)
- Flashing collar
- (sometimes referred to as a roof jack or flashing boot) an accessory flashing used to cover and/or seal soil pipe vents and other penetrations through the roof.
- Flat lock
- a method of interlocking metal panels in which one panel edge is folded back on top of itself and the other panel is folded under, after which the two panels are hooked together. The NRCA Roofing and Waterproofing Manual—Fifth Edition 986 Glossary
- Fleece
- mats or felts composed of fibers, sometimes used as a membrane backer.
- Flood (pour) coat
- the surfacing layer of bitumen into which surfacing aggregate is embedded on an aggregatesurfaced built-up roof.
- Flood test
- the procedure in which a controlled amount of water is temporarily retained over a horizontal surface to determine the effectiveness of the waterproofing system.
- Fluid-applied elastomer
- a liquid elastomeric material that cures after application to form a continuous waterproofing membrane.
- Fly-in
- method of application for roll materials by which the dry sheet is set into the bitumen or adhesive applied to the roof surface.
- FM
- see Factory Mutual Research (FMR).
- Foam stop
- the roof edge treatment upon which SPF is terminated.
- Force
- a strength or energy exerted or brought to bear; cause of motion or change.
- FPL
- Forest Products Laboratory.
- Froth pack
- a term used to describe small, disposable aerosol cans that contain SPF components. Two component froth packs are available to do small repairs for sprayed polyurethane foam-based roofs.
- Top of Page