Building Envelope Glossary

A

AAMA 501.2

A field check of storefront and curtain wall in which a calibrated nozzle sprays water at joints and seams while the inside is watched for leaks. Window and Storefront Water Testing →

AAMA 502 / 503

Field water tests for newly installed windows and doors (502) and storefront or curtain wall (503): water is sprayed on the outside while a chamber creates a pressure difference. Window and Storefront Water Testing →

Air barrier

The continuous layer of materials that stops air from moving through the envelope. Air leaks carry moisture and energy with them. Blower Door Testing →

B

Ballasted roof

A membrane held in place by stone or pavers rather than adhered; ballast must be moved to locate leaks. Electronic Leak Detection →

Below-grade waterproofing

Waterproofing at walls covered by backfill, typically at basements or subterranean parking structures.

Blower door test

A fan mounted in a doorway pressurizes or depressurizes the building to measure how much air leaks through the envelope. Blower Door Testing →

Building envelope

Everything that separates the inside of a building from the outside: roofs, walls, windows, doors, below-grade walls and the waterproofing between them. Also called the building enclosure.

C

CapEx

Capital expenditure: larger, planned spending to repair or replace building components, as opposed to routine maintenance. Property Condition Assessments →

Chamber test

A field water test where an air chamber on one side of a window creates a pressure difference while water is sprayed on the other side, like wind-driven rain. Window and Storefront Water Testing →

Cladding

Exterior wall covering such as brick masonry, lap or panel siding, stucco, EIFS, or metal panel.

Coping cap

The metal cap on top of perimeter parapet walls. If wind removes it, the membrane may peel back.

Cover board

A thin, rigid board under the membrane that protects the insulation and gives the membrane a firm surface.

Curb

The raised frame that rooftop equipment or a skylight sits on. The roof membrane turns up and is flashed against it.

Curtain wall vs. window wall

Curtain wall hangs outboard of the floor slabs (common in high-rise office); window wall sits between slabs and has more joints to maintain. Window and Storefront Water Testing →

D

Delamination

Layers separating from each other, such as a coating lifting off concrete or a membrane releasing from the board below it.

E

Efflorescence

White, salty staining on masonry; a leading indicator that water is trapped in the wall and the internal drainage system is not performing.

EIFS

Exterior Insulation and Finish System: foam insulation board covered with a thin reinforced finish that looks like stucco.

Electronic leak detection (ELD)

Testing that uses an electrical current across a roof or waterproofing membrane to find breaches, often before they leak inside. Low-voltage methods test a wet surface; high-voltage methods test a dry one. Electronic Leak Detection →

EPDM (rubber)

Usually black. Seams use adhesive tape which, while durable, is a wear item that eventually dries out and fails.

Expansion joint

An intentional gap that allows the building to move. Failed joints can leak vertically and affect multiple floors.

F

Fastener plate

The metal disc under a screw that holds insulation or membrane down to the roof deck.

Fenestration

Windows, doors, storefronts and skylights: the openings in a building's exterior walls and roof. Window and Storefront Water Testing →

Flashing

Formed metal or membrane pieces installed at edges, joints and openings to turn water outward so it drains instead of getting into the wall or roof.

I

IGU (insulated glass unit)

A double- or triple-pane glass unit within a window assembly.

Infrared thermography

A camera that shows surface temperature. Wet insulation holds heat differently than dry insulation, so likely wet areas stand out and are then confirmed by other testing. Infrared Thermography →

K

Kick-out flashing

A small angled flashing where a roof edge meets a wall. It sends water into the gutter instead of down behind the siding.

L

Low-slope roof

A roof that is nearly flat. It relies on a continuous membrane, rather than overlapping shingles, to keep water out.

M

Mock-up

A sample of a wall, window or roof assembly built and tested before full installation, so problems are fixed once instead of across the building. Construction QA Site Visits →

Moisture survey

Mapping where materials are wet with meters, infrared and test cuts, so repairs cover the real extent of damage. Infrared Thermography →

O

Overburden

Anything installed on top of a waterproofing membrane, such as pavers, soil, ballast or a green roof. It hides the membrane and makes leaks hard and costly to reach. Electronic Leak Detection →

P

Parapet

The short wall that extends above the roof at its edge.

Penetration

Anything that passes through the roof or wall, such as pipes, vents, conduit or equipment supports. Each one has to be flashed or sealed.

Pitch pocket

A sealant-filled reservoir around irregular roof penetrations. High-maintenance; sealant shrinks and cracks and typically needs attention every 3–5 years.

Property condition assessment (PCA)

A survey of a building's systems that rates their condition and estimates repair and replacement costs, often before a purchase or loan. Property Condition Assessments →

R

Roof deck

The structural surface under the roof insulation and membrane, such as wood, metal or concrete.

Rough order-of-magnitude (ROM)

An early cost range for planning, based on the observed conditions and typical pricing. It is not a contractor bid or a formal estimate. Property Condition Assessments →

S

Sandwich slab

A membrane buried beneath concrete or pavers. It cannot be reviewed without removing the surface, and leak repair costs are often many times the material cost. Electronic Leak Detection →

Scuppers and drain bodies

Roof drainage. Drains are set within the field of the roof and discharge through internal piping; scuppers are set at exterior walls and often drain to gutters.

Seal failure

Loss of the IGU seal allows moist air in and the glass fogs; the unit must be replaced.

Sealant (caulk)

The least expensive material on the building and the most common cause of failure. Quality sealant lasts roughly 7–15 years; lower-grade sealant can fail in under 5.

Service life

How long a system can be expected to keep performing, with normal maintenance, before it needs major repair or replacement. Property Condition Assessments →

Sheathing

The structural panels (usually plywood or OSB) fastened to the framing, behind the WRB and cladding.

Sill, jamb and head

The bottom, side, and top members of a window or door frame. Drainage typically occurs at the sill.

Single-ply membrane

A continuous, waterproof “skin” for the roof. TPO is the most common membrane used in low-slope roof construction.

Spray rack

A frame of nozzles that wets a window or wall evenly during a water test. Window and Storefront Water Testing →

Storefront

A framed glass wall system set between the floor and the structure above, common at ground-floor retail and lobbies. Window and Storefront Water Testing →

Stucco

A cement plaster finish applied over lath on an exterior wall.

Submittal

Product data and shop drawings the contractor sends for approval before installing. Reviewing envelope submittals catches mismatched or missing parts early. Building Envelope Design Review →

Substrate

The surface a material is installed on, such as the roof deck under a membrane or the sheathing under a coating.

T

Test cut

A small, planned opening in a roof or wall to look inside and confirm what testing showed. It is patched after. Forensic Water Intrusion Investigation →

Through-wall flashing and weeps

The wall’s internal drainage: flashing collects water behind the cladding and weeps drain it out. Missing or clogged weeps trap water in the wall.

TPO / PVC (thermoplastic)

Usually white. Seams are heat-welded, creating a monolithic sheet; reflective surfaces reduce cooling loads when kept clean.

Traffic coating

A protective coating on horizontal concrete that keeps water from reaching reinforcing steel. If neglected, rebar can corrode, expand, and crack the concrete.

Transition

Any place where one envelope material or system meets another, such as window to wall or wall to roof. Most leaks start at transitions. Construction QA Site Visits →

V

Vapor retarder

A material that slows water vapor moving through a wall or roof. Where it goes depends on the climate and the wall design.

W

WRB (water-resistive barrier)

The layer behind the cladding that keeps sheathing and interior walls dry while allowing vapor to escape. Improper installation or damage can lead to water-related damage. Construction QA Site Visits →