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Roofing Terminology D-F

DAMPPROOFING- A process used on concrete, masonry or stone surfaces for the purpose of repelling water. Moisture vapor readily penetrates coatings of this type. The main purpose of dampproofing is to prevent the coated surface from absorbing rain water while allowing is to breathe moisture vapor out of the structure.

DEAD LOAD- The constant designed weight (of the roof) and any permanent fixtures attached above or below.

DECK- The base surface to which a roof system is applied.

DECKING- The structural "skin" of a roof over which roofing in applied. Most new homes have decking made of plywood. There are four main types of decking commonly used on residential roofing projects-

PLYWOOD- Plywood is strong, durable, and light. It comes in many grades with ratings from A to D. Use only exterior grade plywood for decking. The thickness of plywood depends on the spacing of the rafters.

OSB- Oriented strand board (OSB) is cheaper than plywood, but not as strong as plywood, and does not hold nails as well as plywood. One side has a slip resistant coating and should be placed facing up.

TONGUE AND GROOVE 2x6- If a roof will be seen from the inside (no ceiling installed), tongue and groove is used. It is a wood decking that provides great insulation without additional rigid roof insulation in moderate climates. Also, the boards can be painted or stained on the inside to match the interior.

STEP SHEATHING- Step sheathing is used alone or in combinations with solid sheathing for installation of tiles or shakes. Step sheathing allows air circulations under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move under the tiles or shakes.

DEFLECT- To bend or deform under weight.

DEW POINT- The critical temperature at which vapor condenses from the atmosphere and forms water.

DIFFUSION- The movement of a substance such as water vapor from regions of high concentration to regions of lower concentration

DIMENSIONAL SHINGLE- A shingle that is textured, or laminated to produce a three-dimensional effect. Also known as Laminated and Architectural Shingles. Please be aware that there are also shingles being produced that can be classified as Dimensional but not as Laminated. These shingles are comprised of a single piece of material rather than two different materials laminated together.

DIMENSIONAL STABILITY- The ability of a material to retain its current properties and to resist a change in size resulting from exposure to temperature changes and moisture.

DORMER- Structure which projects from a sloping roof.

DOUBLE TEE- Refers usually to a pre-cast roof deck panel poured with two fins in its underside to impart flexural rigidity.

DOWNSPOUT- The metal pipe used to drain water from a roof.

DRAWING OUTLINE- A top view drawing, of a building or roof showing only the perimeter drawn to scale.

DRAIN- a device used to carry water off of a roof.

DRAWING DETAIL- A top view drawing, of a building or roof showing the roof perimeter and indicating the projections and roof mounted equipment, drawn to scale.

DRIP EDGE- A device designed to prevent water from running back or under an overhang.

DRIPPAGE- Bitumen material that drips through roof deck joints, or over the edge of a roof deck.

DRY-IN- The process of installing the underlayment in steep slope roofing; Or making a low-slope roof watertight. Does not always mean getting all of the required plies installed.

DRY LAP- A term describing the absence of bitumen between the plies of felt at the overlap in a BURM.

DRY ROT- Wood rot caused by certain fungi. Dry rot can result from condensation build-up, roof leaks that go untended, or from other problems. Dry rot will not remain localized. It can spread and damage any lumber touching the affected area.

DRY SHEET- A ply mechanically attached to wood or gypsum decks to prevent asphalt or pitch from penetrating the deck and leaking into the building below.

DUCT- A cylindrical or rectangular "tube" used to move air either from exhaust or intake. The installation is referred to as "duct work".

DUTCH LAP METHOD- Application of giant individual shingles with the long dimension parallel to the eaves. Shingles are applied to overlap adjacent shingles in each course as well as the course below.

DYNAMIC LOAD- Any moving load on a roof such as people and equipment. Wind can also be considered a Dynamic Load.

EAVE- A roof edge that extends out past the exterior wall line.

EDGE STRIPPING- Roofing material used to seal perimeter edge metal and the roof itself.

EDGE VENTING- The installation of vent material along a roof edge (e.g., Starter Vent) as part of a ventilation system. Edge vent material should be used in conjunction with other venting material (e.g., ridge vent) as it not intended for use by itself.

EFFLORESCENCE- The process by which water leeches soluble salts out of concrete or mortar and deposits them on the surface. Also used as the name for these deposits.

ELASTOMERIC- Properties of a material that will permit it to return to its original shape after being stretched.

ELASTOMERIC COATING- A coating that can be stretched to twice its dimensions and that will return to original when tension is released.

ELONGATION- The ability of a material to be stretched or lengthened.

EMBEDMENT- In roofing, to uniformly press one material into another, such as aggregate into bitumen, roofing felt into bitumen, or granules into a coating.

EMULSION- Fine particles suspended in a liquid solution.

EPDM- Ethylene Propylene Diene Monomer. A single ply membrane consisting of synthetic rubber; usually 45 or 60 mils. Application can be ballasted, fully adhered or mechanically attached.

END LAP- The amount or location of overlap at the end of a roll of roofing felts in the application.

E.V.T. EQUI-VISCOUS TEMPERATURE- The critical temperature at which asphalt reaches the viscosity most favorable to good adhesion when applied in a BUR.

EXHAUST VENT- A device used to vent air from the roof cavity with vents that are installed on or near the higher portions of the roof such as the ridge.

EXPANSION COEFFICIENT- The amount that a specific material will vary in any one dimension with a change of temperature.

EXPANSION CLEAT- A cleat designed to handle thermal movement of the metal roof panels.

EXPANSION JOINT- A device used to make up the motion of expansion and contraction. On large roofs this provision for the movement of the materials forming the walls, roof deck and roof covering is usually made by deliberately separating the building into sections, and covering separation between adjacent sections with the expansion joint to allow movement but keep out the weather. Expansion joints, unlike control joints, penetrate through the roof deck.

EXPOSURE- The portion of a material (shingle or membrane) that is not overlapped by the succeeding ply or course.

EXTRUSION- An item formed by forcing a base metal (frequently aluminum) or plastic, at a malleable temperature, through a die to achieve a desired shape.

EYEBROW- A flat, normally concrete, projection which protrudes horizontally from a building wall; Eyebrows are generally located above windows.

FAÇADE- The front of a building. Frequently, in architectural terms an artificial or decorative effort.

FACTORY MUTUAL FM- A major insurance agency who has established stringent guidelines for maximum construction integrity as it relates to fire and environmental hazards. Their specifications have become industry standards.

FACTORY SEAM- A splice/seam made in the roofing material by the manufacturer. It is preferable during installation to remove these splices from the roof system.  If a splice occurs on a shingle, it should be thrown away.

FASCIA- Any cover board at the edge or eaves of a flat, sloping, or overhanging roof which is placed in a vertical position to protect the edge of the roof assembly.

FASTENERS- A general term covering a wide variety of screws and nails that may be used for mechanically securing various components of a building.

FHA-The Federal Housing Authority. Sets construction standards
throughout the U.S.

FELT- A very general term used to describe composition of roofing ply sheets, consisting of a mat of organic or inorganic fibers unsaturated, impregnated with asphalt or coal tar pitch, or impregnated and coated with asphalt.

FERRULE- A metal sleeve used as a spacer to keep gutter from being beat up when secured to fascia with spikes.

FIBERGLASS INSULATION- Insulation composed of glass fibers used to insulate walls and roofs. It can be rigid board or blanket insulation.

FIELD OF THE ROOF- Refers to the central part of a roof away from the perimeter.

FIELD SEAM- A non-factory material seam made by joining overlapping seams together with adhesives, heat welders, or other means.

FILM- A membrane or sheeting material with a nominal thickness of 10 mils or less.

FILM THICKNESS- The thickness of a membrane or coating that is expressed in mils (thousandths of an inch).

FIN- A sharp protrusion in a roof deck that can damage roof components.

FIRE WALL- Any wall built for the purpose of restricting or preventing the spread of fire in a building. Such walls of solid masonry or concrete generally sub-divided a building from the foundations to two or more feet above the plane of the roof.

FISHMOUTH- A characteristic opening at the exposed lap edge of BUR felts due to loss of bond or wrinkling of the felt.

FLAKE- A scale like particle. To lose bond from a surface in small thin pieces. Sometimes a paint film "flakes".

FLANGE- A projection edge of a roof component such as flashings, skylight frames, pre-manufactured curbs, etc. Usually refers to the part that sits on the roof surface.

FLASHING- Connecting devices that seal membrane joints at expansion joints, walls, drains, gravel stops, and other places where the membrane is interrupted or terminated.

FLASHING BASE- The upturned edge of the watertight membrane formed at a roof termination point by the extension of the felts vertically over the cant strip and up the wall for a varying distance where they are secured with mechanical fasteners.

FLASHING CEMENT- A trowelable mixture of solvent-based bitumen and mineral stabilizers.

FLASHING COLLAR- A flashing component used to seal soil pipe vents, hot stacks or other roof penetrations.

FLASHING, COUNTER- The formed metal secured to a wall, curb, or roof top unit to cover and protect the upper edge of a base flashing and it's associated fasteners.

FLASH POINT- The critical temperature at which a material will ignite.

FLASHING, THRU-WALL- Flashing extended completely through a masonry wall. Designed and applied in combination with counter flashings to prevent water which may enter the wall above from proceeding downward in the wall or into the roof deck or roofing system.

FLAT SEAM- A seam at the junction of sheet metal roof components that has been bent at the plane of the roof.

FLOOD COAT- The surfacing layer of bitumen into which aggregate is embedded on an aggregate-surfaced built-up roof. A flood coat is applied at an approximate rate of 45 to 60 pounds per square (100 square feet).

FLOP- Cutting of felts into strips, coating the deck side with bitumen and placing (flopping) the felt onto the deck.

FLASHING, STEP- Individual small pieces of metal flashing material used to flash around chimneys, dormers, and such projections along the slope of a roof. The individual pieces are overlapped and stepped up the vertical surface.

FOLDED SEAM- In sheet metal work, a joint between sheets of metal wherein the edges of the sheets are crimped together and folded flat.

FULLY ADHERED- A completely attached (adhered) roof membrane