Reference
Plain-language definitions of building envelope and roofing terms, from air barriers and flashing to ASTM E1105 water testing, WUFI and roof moisture surveys.
Roof and wall reports, test results and repair proposals come with their own vocabulary. This glossary explains the terms building owners, facility managers and architects most often meet — roofing systems and their parts, how walls and windows keep out water and air, the tests used to check them, and the process of designing, building and assessing the building enclosure — in plain language.
A field water check for installed curtain walls, storefronts and sloped glazing, in which water from a specified nozzle is directed along joints and framing members to look for leaks. Unlike ASTM E1105 it does not apply an air pressure difference, which makes it quicker to run on many locations.
How Inspec helps:Building envelope testing
The materials and joints that together stop uncontrolled air from flowing through the building enclosure. Air carries heat and moisture with it, so gaps in the air barrier cause energy loss, drafts and condensation; continuity at transitions between walls, windows and the roof is what makes it work.
How Inspec helps:Building enclosure design
A standard field test method for measuring air leakage through installed exterior windows and doors. A test chamber is sealed over the unit, a pressure difference is applied, and the air flow needed to hold it is measured.
How Inspec helps:Building envelope testing
A standard field test method for water penetration of installed windows, skylights, doors and curtain walls. Water is sprayed on the exterior while an air pressure difference is applied across the assembly, and the interior side is watched for leaks.
How Inspec helps:Building envelope testing
River rock or concrete pavers laid over a loose roof membrane to hold it down by weight instead of adhesive or fasteners. Ballast shields the membrane from sunlight and traffic, but the structure must be able to carry it, wind can scour it from corners and edges, and it hides the membrane, which makes leaks harder to trace.
The roof membrane, or a compatible flashing sheet, turned up the face of a wall, curb or other vertical surface where it meets the roof. It closes the joint between the roof and the vertical surface and is normally protected at its top edge by counterflashing.
Waterproofing applied to foundation walls, slabs and other construction below ground, where it may face water under pressure from the surrounding soil. Positive-side systems go on the face that meets the water, negative-side systems on the interior face, and because the membrane is buried, it is far easier to get right during construction than to repair later.
How Inspec helps:Waterproofing consulting
A raised, often spongy area of a roof membrane where the layers have separated and trapped air or moisture between them. Blisters grow as the trapped air and moisture expand in the heat, and once broken they can let water into the roof.
How Inspec helps:Roof failure analysis
A test that uses a calibrated fan, set into a door or other opening, to pressurize or depressurize a building or part of one and measure how much air leaks through its enclosure. Combined with smoke or infrared imaging, it also helps find where the leaks are.
How Inspec helps:Building envelope testing
The physical separator between a building's interior and the outdoor environment: roof, walls, windows, doors and below-grade construction. It has to control water, air, heat and vapor while carrying its own structural loads.
How Inspec helps:Building envelope consulting
A quality-focused process that checks, from design through construction, that the building enclosure will meet the owner's performance requirements. It typically combines design review, submittal review, mock-ups, field testing and construction observation, so that problems are caught before they are built in.
How Inspec helps:Building enclosure commissioning
Another name for the building enclosure, and the more common one in everyday use. The two terms are generally used interchangeably; some building scientists prefer "enclosure" because it describes a system that separates the inside from the outside rather than simply wrapping the building.
How Inspec helps:Building envelope consulting
A low-slope roof made of several plies of reinforcing felt laminated together with hot asphalt or coal-tar pitch, usually finished with a flood coat and embedded gravel. The multiple plies give redundancy, and the gravel protects the bitumen from sunlight, weather and foot traffic.
How Inspec helps:Roof condition assessment
A bitumen used instead of asphalt between the plies of some built-up roofs, surfaced with gravel. It softens and flows in warm weather, which lets small cracks close on their own and suits it to dead-level roofs, but it is only appropriate on roofs that are flat or very nearly so and repairs need compatible materials.
How Inspec helps:Roof condition assessment
Water that forms when warm, moist air meets a surface below its dew point. Inside walls and roofs it can wet insulation and sheathing, corrode metal and support mold, and it is often mistaken for a leak — telling the two apart matters because the fixes are different.
How Inspec helps:Moisture intrusion analysis
Periodic site visits by a design professional or consultant to observe whether the work generally follows the contract documents, and to report what they find. It is not continuous supervision, and the contractor remains responsible for construction means, methods and quality.
How Inspec helps:Construction observation and administration
The cap on top of a parapet or freestanding wall, made of metal, stone or precast concrete and shaped to shed water off the wall top. Open joints, loose fasteners or missing sealant at the coping can let water straight into the wall below.
A small sample cut through the roof assembly down to the deck and then patched. It shows what layers the roof contains, the type and thickness of the insulation, and whether it is wet — information that thermal images and drawings cannot confirm on their own.
How Inspec helps:Roof moisture analysis
A piece of flashing, usually metal, fixed to or set into the wall above the base flashing and lapped down over its top edge. It sheds water over the base flashing while letting the roof and wall move independently of each other.
A small ridged area built up on a roof to divert water around an obstruction, such as a curb or chimney, or toward the drains in the valleys between them. On low-slope roofs crickets are usually formed with tapered insulation.
A non-load-bearing exterior wall, usually aluminum framing with glass or panel infill, hung from the building structure and often spanning several floors. It carries its own weight and wind loads back to the structure, and its performance depends on its gaskets, sealants, internal drainage and the joints at its edges.
How Inspec helps:Exterior wall and window consulting
The temperature at which air holds as much water vapor as it can and water begins to condense. Any surface in a building assembly that is colder than the dew point of the air reaching it will collect condensation.
A white, powdery or crystalline deposit on masonry, stone or concrete, left when water moving through the material dissolves salts and then evaporates at the surface. It is usually harmless in itself, but it shows that water is moving through the wall.
How Inspec helps:Facade consulting
A family of test methods that use a low- or high-voltage electrical current to find breaches in a roof or waterproofing membrane, because current passes through a hole where the intact membrane insulates. It can locate small defects precisely, but whether it works depends on the membrane and on what lies beneath it.
How Inspec helps:Roof moisture analysis
A synthetic rubber single-ply membrane (ethylene propylene diene monomer) that stays flexible through hot and cold weather. Its sheets are joined with tape or adhesive rather than welded, so seams, laps and flashings are where leaks most often start.
How Inspec helps:Commercial roof inspection
A survey of the condition of a building's systems — enclosure, structure, and often mechanical and electrical — that identifies deficiencies and estimates when repairs or replacements will be needed. Owners use it to prioritize work and build a multi-year capital plan.
How Inspec helps:Facility condition assessments
An open wrinkle along the edge of a lapped felt or membrane that has lifted into a shape like a fish's mouth. The opening breaks the seal of the lap and gives water a direct path into the roof.
How Inspec helps:Roof failure analysis
The pieces of membrane, metal or other material that seal the joints and transitions in a roof or wall — at walls, curbs, penetrations, edges and changes of plane. Flashings are where different materials and trades meet, which is why so many leaks begin at them.
How Inspec helps:Commercial roof inspection
Classifications that FM Approvals and UL assign to roof assemblies tested for performance such as fire resistance, wind uplift or hail. A rating applies to the tested assembly as a whole — deck, insulation, attachment and membrane together — so substituting a component can mean the roof no longer matches it; insurers and codes may require a particular rating.
An engineering investigation into why a building component leaked, deteriorated or failed. It draws on document review, site observation, testing and, where needed, openings into the construction, and its findings support repair design, insurance claims or dispute resolution.
How Inspec helps:Forensic building investigation
A calculation of how heat and moisture move through a wall or roof assembly over time, using real climate data and material properties. It predicts whether moisture will accumulate or dry out, and is used to choose materials and layer order before construction or to understand a problem after it.
How Inspec helps:Hygrothermal modeling (WUFI)
A thermal-imaging scan of a low-slope roof, usually after dark following a sunny day, when wet insulation holds heat longer than dry insulation and shows as warmer areas. The suspect areas are then confirmed with core cuts or moisture meters and mapped so that only wet material needs to be removed.
How Inspec helps:Roof moisture analysis
Imaging surface temperatures with a thermal camera to reveal what the eye cannot see, such as missing insulation, air leakage, thermal bridges and wet materials. It needs a meaningful temperature difference to work, and an experienced interpreter, because reflections and surface finishes can mislead.
How Inspec helps:Thermal imaging for building inspections
A roof that is flat or nearly flat, as on most commercial, institutional and industrial buildings. Because water drains slowly across it, a low-slope roof depends on a continuous waterproof membrane rather than overlapping pieces that shed water by gravity.
How Inspec helps:Commercial roof inspection
A full-size sample of a wall, window or roof assembly built before, or at the start of, production work. It is used to confirm appearance, sequencing and details, and is often tested for water and air leakage so that problems are fixed once rather than repeated across the building.
How Inspec helps:Building enclosure commissioning
Factory-made roofing rolls of asphalt modified with polymers (SBS or APP) around a reinforcing mat, usually installed in two or more plies with a cap sheet surfaced in mineral granules. Sheets can be torch-applied, hot-mopped, set in cold adhesive or self-adhered, and the quality of the laps depends heavily on installation.
How Inspec helps:Roof condition assessment
Any unwanted water entering a building or its assemblies, whether from rain leaks, rising groundwater, plumbing or condensation. Finding the true source matters more than stopping the visible symptom, because water often travels a long way from where it enters to where it appears.
How Inspec helps:Moisture intrusion analysis
The part of an exterior wall that extends above the roof line. Parapets are exposed to weather on both faces and the top, so their coping, flashings and masonry are frequent sources of water entering the roof and the wall.
A survey of a parking lot, drive or road that records the type, severity and extent of distresses such as cracking, rutting, potholes and raveling, often summarized as a numerical condition index. It shows which areas need routine maintenance, rehabilitation or full reconstruction, and when.
How Inspec helps:Pavement engineering and consulting
A waterproofed structural deck over occupied or parking space that is covered by pavers, concrete topping, soil or landscaping. The waterproofing is buried under the finished surface, so drainage, flashing at edges and penetrations, and testing before it is covered are critical.
How Inspec helps:Waterproofing consulting
Water that stays on a roof well after rain has stopped and conditions would normally have dried it. Ponding adds weight to the structure, can shorten the life of some membranes and makes any leak worse; it usually points to deflection, blocked drains or inadequate slope.
How Inspec helps:Commercial roof inspection
A thermoplastic single-ply membrane (polyvinyl chloride) with heat-welded seams. It resists grease and many chemicals, which suits it to roofs near restaurant exhausts and some industrial processes, but it must be kept separated from asphalt and other materials it is not compatible with.
How Inspec helps:Commercial roof inspection
A wall design with an air space between the outer cladding and the water-resistive barrier behind it. Water that gets past the cladding drains down the cavity and out, and the space lets the wall dry, rather than relying on the outer face to be perfectly watertight.
How Inspec helps:Exterior wall and window consulting
The general term for putting a new roof on an existing building, either by recovering over the old roof or by tearing it off and replacing it. The right choice depends on the condition of the existing roof, how much of it is wet, the structure and what the building code allows.
How Inspec helps:Roof consulting
A systematic evaluation of a roof's membrane, flashings, drainage, insulation and deck, recorded so that its condition can be compared over time. It usually leads to a recommendation to maintain, repair, recover or replace, and helps owners plan and budget for that work.
How Inspec helps:Roof condition assessment
Installing a new roof membrane, often with a cover board or new insulation, over an existing roof that is left in place. Building codes restrict when a recover is allowed, for example where the existing roof is wet or deteriorated or has already been recovered, so the existing roof has to be surveyed first.
How Inspec helps:Roof condition assessment
Removing the existing roof down to the deck and installing a new roof system. It costs more than a recover but exposes the deck for inspection and repair, removes wet insulation, and allows drainage to be redesigned.
How Inspec helps:Roof consulting
An opening through a parapet or roof edge that drains water off the roof, often into a gutter or downspout. Scuppers serve either as the primary drainage or as overflows that relieve the roof if drains become blocked.
A joint between building components filled with an elastic sealant, usually over a backer rod, and sized to accommodate movement. Sealant joints fail when the sealant loses adhesion to the surfaces, tears within itself, or simply ages out, and they need periodic inspection and replacement.
How Inspec helps:Exterior wall and window consulting
The overlap where one sheet of roofing meets the next, and the joint sealing them together — taped, adhered, heat-welded or set in bitumen, depending on the system. Seams and laps depend on workmanship and are among the most common sources of roof leaks.
How Inspec helps:Commercial roof inspection
A low-slope roof covering made of one layer of factory-made sheet, joined at the seams in the field. The common types are EPDM rubber and the thermoplastics TPO and PVC, and they can be fully adhered, mechanically fastened or held down with ballast.
Pieces of concrete, masonry or stone flaking, popping or breaking away from the surface. Common causes include freeze-thaw cycles in saturated material and corrosion of embedded steel, which expands as it rusts; on a facade, spalling can also become a falling-debris hazard.
How Inspec helps:Facade consulting
A metal roof of steel, aluminum or copper panels joined by raised interlocking seams and held down by concealed clips rather than exposed fasteners. The raised seams shed rain and snow and the clips let panels move with temperature; leaks usually start at penetrations, trim and flashings, and the roof needs enough slope for the panel profile.
How Inspec helps:Commercial roof inspection
A lighter glazed framing system, typically installed between the floor and the structure above at ground level entrances and shop fronts. It relies more on sealant and on a properly flashed sill than a curtain wall does, and it is prone to leaks when used in more exposed locations than it was designed for.
How Inspec helps:Exterior wall and window consulting
A stormwater best management practice: a structural feature, such as a detention basin, bioswale or permeable pavement, or an operational practice that controls the amount and quality of runoff leaving a site. Many BMPs must be inspected and maintained regularly to keep working and to meet permit requirements.
How Inspec helps:Stormwater inspections and management
The design team's review of the contractor's shop drawings, product data and samples for general conformance with the design. For the enclosure it is where incompatible materials, missing details and substitutions are most cheaply caught.
How Inspec helps:Construction observation and administration
Rigid roof insulation boards manufactured with a built-in slope, laid in a planned layout to move water toward drains, scuppers or gutters on a roof deck that is flat. It is a common way to reduce ponding when a roof is replaced.
How Inspec helps:Roof condition assessment
A path of more conductive material — such as a steel stud, slab edge, balcony or window frame — that passes through or around the insulation. Thermal bridges lose heat, create cold spots on interior surfaces, and can lead to condensation and mold.
How Inspec helps:Building enclosure design
A flashing membrane or metal built into a masonry or cavity wall — at its base, at shelf angles, over lintels and under sills — to collect water in the wall and direct it out through weeps. Missing, damaged or poorly lapped through-wall flashing is a common cause of leaks and masonry deterioration.
How Inspec helps:Facade consulting
A thermoplastic single-ply membrane (thermoplastic polyolefin), typically white, whose seams are heat-welded into one continuous sheet. Its reflective surface reduces heat gain, and formulations differ between manufacturers, so seam welds and flashing details depend on installation quality.
How Inspec helps:Commercial roof inspection
The movement of water vapor through materials from areas of higher vapor pressure to lower, typically from warm and humid toward cool and dry. Its direction can reverse with the seasons, and in summer sun can drive moisture stored in wet cladding such as brick inward.
How Inspec helps:Hygrothermal modeling (WUFI)
A material that slows the diffusion of water vapor through an assembly, used to keep vapor from reaching surfaces cold enough for it to condense. Where it belongs, and how restrictive it should be, depends on the climate, the interior conditions and the rest of the assembly — a vapor retarder on the wrong side can trap moisture.
How Inspec helps:Hygrothermal modeling (WUFI)
The layer behind the cladding that stops water that gets past the cladding and directs it back out, usually a sheet membrane, fluid-applied coating or coated sheathing. It must be lapped and flashed so water drains outward at windows, penetrations and the base of the wall, and it often doubles as the air barrier.
How Inspec helps:Exterior wall and window consulting
A small opening that lets water drain out of a wall cavity, window frame or glazing system. Weeps work together with flashings and must be kept clear; blocked or missing weeps can trap water inside the wall.
A glazed wall made of units that span from one floor slab to the next, installed floor by floor, with the slab edges covered by trim or panels. It is common on residential and mixed-use towers, and the joints at each slab edge are critical to keeping water and air out.
How Inspec helps:Exterior wall and window consulting
The upward suction wind creates as it flows over and around a roof, which tries to peel the roof system off the building. The forces are highest at corners and perimeters, so attachment is usually increased there, and wind damage tends to start at edges.
How Inspec helps:Roof failure analysis
A widely used family of hygrothermal simulation software developed by the Fraunhofer Institute for Building Physics. It models heat and moisture transport through building assemblies hour by hour under real weather, going well beyond simple dew-point calculations.
How Inspec helps:Hygrothermal modeling (WUFI)