GLOSSARY
Roof Inspection and Leak Detection Glossary
61 terms in plain English, from flashing and ponding to thermography and underlayment.
- 61 terms
A
- Algae
- Microscopic growth that forms dark streaks on damp roofs, most often on shaded or north-facing slopes. It is mostly cosmetic but can speed wear in severe cases.
- Attic Ventilation
- The flow of air through an attic, usually in at the eaves and out at the ridge, that removes heat and moisture from beneath the roof.
B
- Base Flashing
- Metal or membrane that turns up a wall or curb at the edge of a roof to seal the joint between roof and wall.
- Blistering
- Raised bubbles on a roof surface, caused by trapped moisture or air. On shingles it can mean granule loss; on flat roofs it can mean trapped moisture.
- Built-Up Roof
- A flat roof made of alternating layers of asphalt and reinforcing felt, often topped with gravel or a coating.
C
- Cap Sheet
- The top layer of a modified bitumen roof, usually surfaced with granules to protect against sun and weather.
- Capacitance Meter
- A tool that measures moisture by detecting changes in electrical properties of roofing materials.
- Capital Planning
- Budgeting years ahead for roof repair and replacement using condition ratings and expected remaining life.
- Coping
- A cap on top of a parapet wall that sheds water and protects the wall edge.
- Counter-Flashing
- Flashing that overlaps base flashing to shed water over it, often set into a wall or chimney.
- Cricket
- A small peaked structure built behind a chimney or curb to shed water around it instead of letting it collect.
- Curb
- A raised frame on a roof that supports equipment such as a skylight or rooftop unit and is flashed into the roof.
D
- Decking
- The structural sheets or boards, often plywood or OSB, that cover the rafters and carry the roofing material.
- Delamination
- Separation of the layers of a material, such as plies in a roof membrane or the surface from the mat in a shingle.
- Dormer
- A small structure that projects from a sloped roof, often with a window, creating extra joints that need flashing.
- Drip Edge
- Metal flashing along the roof edge that directs water away from the fascia and into the gutter.
- Drone Survey
- Inspecting a roof by flying a camera-equipped drone to capture images of surfaces, seams and details.
E
- Eave
- The lower edge of a roof that overhangs the wall.
- Electronic Leak Detection
- A method that uses a low-voltage electrical field across a membrane to find openings, even tiny ones, in a flat roof.
- EPDM
- A synthetic rubber membrane used on flat roofs, usually black, with seams joined by tape or adhesive.
F
- Fascia
- The board that runs along the roof edge, to which gutters are usually attached.
- Flashing
- Thin metal or membrane used to direct water away from joints, such as around chimneys, valleys, walls and penetrations.
G
- Granules
- The small mineral particles on the surface of asphalt shingles that protect against sun and add color. Loss of granules is a sign of wear.
H
- Hail Bruise
- A round, soft impact spot on a shingle where granules were knocked off and the mat may be cracked beneath.
I
- Ice Dam
- A ridge of ice at the roof edge that can back water up under shingles when snow melts and refreezes.
- Infrared Thermography
- Using a thermal camera to see temperature differences that can reveal wet insulation under a roof surface.
K
- Kick-Out Flashing
- A bent piece of flashing at the end of a roof-to-wall joint that directs water into the gutter instead of behind the siding.
M
- Modified Bitumen
- A flat roofing material made of asphalt with polymers added, installed in sheets by torch, adhesive or cold process.
- Moisture Survey
- A systematic scan of a roof, using thermal, capacitance or other tools, to map where moisture is in the insulation and deck.
N
- Nuclear Moisture Gauge
- A specialized instrument sometimes used by licensed operators to estimate moisture in roof insulation. Many inspectors prefer other methods.
P
- Parapet
- A low wall that extends above the roof edge on a flat roof, requiring flashing and sound coping to stay watertight.
- Penetration
- Anything that passes through a roof, such as a vent pipe, chimney, skylight or conduit, each needing flashing or sealing.
- Pipe Boot
- A rubber or metal collar that seals the opening around a vent pipe where it passes through the roof. Rubber collars often crack with age.
- Pitch
- The steepness of a roof, usually expressed as inches of rise per twelve inches of run.
- Ponding
- Water that stays on a flat roof for an extended time after rain, often a sign of drainage or structural issues.
- PVC Membrane
- A single-ply roofing sheet with heat-welded seams, valued for chemical resistance.
R
- Rake
- The sloped edge of a roof along a gable end.
- Remaining Life
- An estimate of how many more years a roof is likely to perform, based on its age, materials, condition and exposure.
- Ridge Cap
- The shingles or metal that cover the peak where two roof slopes meet.
- Roof Age
- The number of years since the current roofing was installed, one factor in estimating remaining life along with condition.
- Roof Cement
- A sticky asphalt-based sealant used for small repairs, which often fails if used as a long-term fix.
- Roof Condition Report
- A written record, usually with photos, that summarizes a roof’s condition, defects and recommended actions.
- Roof Deck Moisture
- Water within the roof deck that can cause softening, rot and fastener corrosion.
- Roof Penetration Flashing
- Flashing designed to seal around objects that pass through a roof surface.
- Roof Warranty
- A document from a manufacturer or installer describing what repairs or replacements they will cover and for how long. Terms vary and conditions apply.
S
- Scupper
- An opening through a parapet wall that lets water drain off a flat roof.
- Seam
- The joint between two sheets of roofing membrane or metal panels, a common place for leaks if poorly made or aged.
- Shingle Creasing
- A horizontal fold in a shingle caused by wind lifting it, which can crack the mat and lead to loss.
- Skylight Curb
- The raised frame that a skylight sits on, flashed into the surrounding roof.
- Soffit
- The underside of the roof overhang, often vented to allow air into the attic.
- Soft Metals
- Gutters, vents and flashings that dent easily and help show hail size and direction after a storm.
- Standing Seam
- A metal roof system with raised seams that interlock, with fasteners hidden under the panels.
- Step Flashing
- Individual pieces of flashing layered with shingles along a sidewall to seal the joint between roof and wall.
T
- Thermal Imaging
- Photographing surface temperatures to find hidden moisture, missing insulation or air leaks.
- TPO
- Thermoplastic polyolefin, a white single-ply roofing membrane with heat-welded seams used widely on commercial roofs.
U
- Underlayment
- A protective layer beneath the roofing material that adds a second barrier against water.
V
- Valley
- The inside angle where two roof slopes meet, carrying a lot of water and prone to leaks and debris.
- Vapor Barrier
- A layer that limits moisture movement through a roof or ceiling assembly.
W
- Water Test
- A controlled test where water is applied in stages to different roof areas while someone watches inside to trace a leak.
- Wet Insulation
- Insulation that has absorbed moisture, losing its performance and often hiding a leak source in flat roofs.
- Wind Uplift
- Suction force that pulls on roofing as wind passes over it, strongest at edges, corners and ridges.
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