Home Improvement Glossary
Plain-English definitions for 47 terms you\'ll encounter when reading cost guides, contractor quotes, and insurance claims. Each entry links to the relevant cost guide where the term appears in practice.
A
ACV (Actual Cash Value)
An insurance settlement method that pays the depreciated value of damaged property, not the cost to replace it. For a 15-year-old asphalt roof damaged by hail, ACV pays roughly half what a new equivalent roof costs. Compare with RCV (Replacement Cost Value).
See: Storm Damage Insurance Claim Guide · Foundation Damage Insurance Claim
Architectural shingle
A multi-layer asphalt shingle with random heavier "lower layer" patches creating a dimensional, three-dimensional appearance. Replaced 3-tab shingles as the residential standard around 2010. Lifespan 25-30 years; premium variants reach 50 years.
Asphalt overlay (re-roof)
Installing new asphalt shingles directly over existing shingles without tear-off. Saves $1-$2 per sqft but reduces new roof lifespan 5-10 years, hides underlying deck damage, and is prohibited by code in many jurisdictions after a single existing layer.
B
Bowing wall
A basement foundation wall pushed inward by lateral soil pressure. Indicates an active structural problem; if unaddressed, can lead to wall collapse. Repaired with carbon fiber straps (under 2 inches of bow) or wall anchors (severe).
C
Carbon fiber strap
A 4-6 inch wide strip of carbon fiber fabric epoxied vertically across a bowed foundation wall to provide tensile strength. Prevents further inward movement but doesn't straighten existing bow. Best for walls bowed less than 2 inches. Cost: $400-$800 per strap, 4-12 needed per wall.
Class 4 impact rating
A UL 2218 impact resistance rating designating shingles that withstand a 2-inch steel ball dropped from 20 feet without cracking. Often qualifies homeowners for 10-25% insurance discount in hail-prone regions.
See: Architectural Vs 3 Tab Shingles · Asphalt Vs Metal Roof
ColorPlus
James Hardie's factory-applied baked-on finish in 700+ colors with 15-year limited warranty against fading, chipping, or peeling. Premium of $1.50-$3/sqft over field-painted Hardie. Significantly outperforms site-painted finishes for color longevity.
Control joint
An intentional groove cut or formed in concrete slabs at planned intervals (typically every 8-12 feet) to concentrate cracking at the joint rather than randomly across the slab. A 4-inch slab typically gets joints cut 1 inch deep within 6-12 hours of pour.
D
Decking (roof)
The structural plywood or OSB layer between roof rafters and shingles. Modern code requires minimum 7/16" thickness (1/2" is standard). Damaged decking must be replaced before installing new shingles; typically 5-15% of an aging roof needs partial replacement during reroofing.
Drip edge
A metal flashing installed along roof eaves to direct water away from the fascia board. Required by current building code. Replacement during a roof tear-off is standard; partial replacement costs $400-$1,200 for full perimeter.
E
Egress window
A basement window meeting code requirements for emergency exit: minimum opening dimensions (typically 5.7 sqft for net clear opening), height from floor, and clear well outside. Required for any habitable basement room. New egress window installation: $2,500-$5,000.
Energy Star Most Efficient
A higher tier than standard Energy Star certification, recognizing products in the top performance percentile. Required for the federal 25C tax credit on windows (not just standard Energy Star).
See: Energy Star Window Tax Credit · Ira Tax Credit Home Improvement
Expansive soil
Clay-based soil that shrinks when dry and swells when wet, causing foundation movement. Common in Texas, Oklahoma, parts of Colorado and California. Drives the majority of foundation repair claims in those regions.
F
Fiber cement
A composite siding material made from cement, sand, and cellulose fibers. Non-combustible, dimensionally stable in extreme temperatures, lasts 40-50+ years. James Hardie is the dominant US brand; Allura is the main alternative.
Fibrex
Andersen's proprietary window frame material: a blend of reclaimed wood fiber and PVC. Performs better than pure vinyl in temperature extremes; backbone of Andersen's 100 Series and Renewal product lines.
See: Andersen Windows Series Comparison · Andersen Vs Pella Vs Marvin
Flashing
Sheet metal pieces installed at roof transitions (chimneys, vents, valleys, wall intersections) to prevent water from entering. Approximately 40% of all roof leaks originate at failed flashing — typically the first roof component to need repair.
Frost line
The maximum depth at which ground water freezes in a region. Building footings must extend below this line to prevent frost heave. Frost line ranges from 0 inches (Florida) to 60+ inches (North Dakota). Affects foundation costs significantly.
See: Foundation Repair
H
Helical pier
A steel shaft with helical (screw-shaped) plates welded near the bottom, driven into the ground using hydraulic torque equipment until reaching stable load-bearing soil. The most common modern foundation underpinning method. Cost: $1,500-$2,500 per pier installed.
See: Foundation Pier Installation Cost · Settling Foundation Repair Cost
Hydrostatic pressure
Pressure from groundwater pushing against basement walls and foundation. The most common cause of basement leaks and bowing walls. Addressed by exterior drainage (best), interior drainage tile, or wall reinforcement.
See: Basement Waterproofing Cost · Bowing Basement Wall Repair Cost
I
Ice dam
A ridge of ice forming at the edge of a roof in winter, blocking melted snow from draining and forcing water back under shingles. Causes leak damage to flashing, decking, and ceilings. Repair: $400-$1,500; prevention through proper attic insulation and ventilation.
J
J-channel
A J-shaped vinyl trim piece installed around windows, doors, and at roof intersections to receive the end of siding panels. Holds the cut edge of siding cleanly. Replaced or supplemented during siding replacement.
See: Vinyl Siding Installation · Vinyl Siding Labor Cost Per Square
Joist
A horizontal framing member supporting a floor or ceiling. Floor joists typically span 12-20 feet between supports. In foundation repair, sagging joists may require sistering (adding new joists alongside) or full replacement.
L
Lap siding
Horizontal siding planks overlapping the row below, creating the traditional clapboard look. Available in vinyl, wood, fiber cement (Hardie HardiePlank), and engineered wood. The dominant US residential siding style.
Low-E coating
A microscopically thin metallic coating on window glass that reflects infrared heat while allowing visible light to pass. Standard on quality residential windows; required for the 25C tax credit. Roughly 30-50% reduction in heat transfer through the glass vs uncoated.
M
Mudjacking
A method of lifting settled concrete slabs by injecting a sand-cement slurry under the slab through small holes. Slower cure than polyurethane foam alternative; cheaper material. Cost: $500-$1,500 per affected slab area.
See: Concrete Slab Crack Repair · Settling Foundation Repair Cost
N
NFRC label
A standardized window energy performance label from the National Fenestration Rating Council, showing U-factor, SHGC, Visible Transmittance, Air Leakage, and Condensation Resistance. Required for Energy Star and IRA tax credit eligibility verification.
P
Pier and beam
A foundation type using vertical piers (concrete or wood) supporting horizontal beams that carry floor joists. Common in older US homes (pre-1960). Repair typically involves shimming, replacing piers, or sistering beams.
Polyurethane injection
A foundation crack repair method using expanding polyurethane foam injected under pressure. Foam expands to fill irregular gaps and remains flexible — ideal for active (still-moving) cracks. Compare with epoxy injection which bonds rigidly. Cost: $500-$1,800 per crack.
Prorated warranty
A warranty that pays declining percentages of replacement cost as the product ages. Typical pattern: full coverage years 1-5, then declining linearly. Most "lifetime" residential warranties (shingles, vinyl siding, windows) are prorated after year 5-10.
See: Vinyl Siding Lifespan · Architectural Vs 3 Tab Shingles
R
R-value
A measure of thermal resistance — higher numbers indicate better insulation. Standard fiberglass batt insulation in walls: R-13 to R-21. Insulated vinyl siding adds R-2 to R-5. Insulated garage doors range R-6 to R-18. Higher R-values reduce energy use.
See: Insulated Vinyl Siding Cost · Insulated Garage Door Cost
RCV (Replacement Cost Value)
An insurance settlement method paying the cost to replace damaged property with new equivalent, without depreciation deduction. Premium of 10-25% over ACV coverage. Standard for most modern homeowners policies; ACV is the older alternative.
Roof square
A roofing industry unit of measurement equal to 100 square feet of roof surface. Used for material quantification and labor pricing. A typical 2,200 sqft home has 22-25 squares of roof depending on slope and complexity.
See: Roof Replacement
S
Sealcoating
Application of a protective coating to asphalt driveway surfaces, blocking UV penetration and water infiltration. Extends asphalt lifespan 5-10 years. Recommended every 3-5 years. Cost: $0.15-$0.25/sqft pro; $0.05-$0.10/sqft DIY.
Section 25C credit
The federal Energy Efficient Home Improvement Credit covering 30% of qualified cost for windows ($600/yr), doors ($500/yr), insulation, HVAC, and heat pumps ($2,000/yr separate cap). Overall annual cap: $1,200 base + $2,000 heat pump.
See: Ira Tax Credit Home Improvement · Energy Star Window Tax Credit
Section 25D credit
The federal Residential Clean Energy Credit covering 30% of qualified cost for solar PV, geothermal heat pumps, battery storage (3+ kWh), wind, and fuel cells. NO annual cap; unused credits carry forward to future tax years.
Sheathing
The plywood or OSB layer covering wall studs or roof rafters, providing structural rigidity and a nailing surface for exterior finishes. Modern code requires minimum 7/16" thickness for both walls and roof.
Slab foundation
A concrete foundation poured directly on grade (not on a raised structure). Common in the South and warm climates. Cheaper than basement or crawl space foundations but more difficult to access for plumbing/electrical repair.
Soffit
The underside of a roof overhang (the eave). Often vented to allow attic airflow. Damage to soffit (rot, animal entry) is common in older homes. Replacement: $5-$15 per linear foot.
See: Roof Replacement
Step flashing
A series of L-shaped metal pieces installed at the intersection of a roof slope and a vertical wall (chimney sides, dormer walls). Each piece tucked under one shingle row, creating a stair-step pattern. Improper step flashing is the #1 cause of wall-to-roof leaks.
Sump pump
A pump installed in a basement sump pit to remove groundwater that collects there. Standard residential capacity 1/3 to 1/2 horsepower. Lifespan 7-10 years. Battery backup add-on essential for areas with power outages.
T
Tear-off
Removal of existing roof shingles and underlayment down to the deck before installing new roofing. Industry standard for replacement; allows deck inspection and proper installation. Adds $1-$2/sqft over overlay (which is increasingly restricted by code).
Torsion spring
A tight steel coil mounted on a horizontal shaft above a garage door, storing energy through twisting tension to counterbalance the door's weight. Dominant modern residential design. Standard 10,000-cycle springs last 4-7 years in typical use.
See: Torsion Vs Extension Spring · Garage Door Spring Lifespan
U
U-factor
A window energy rating measuring heat transfer through the entire window assembly (glass + frame). Lower numbers indicate better insulation. Energy Star Most Efficient windows: U-factor 0.20 or lower in most climate zones.
Underlayment (roof)
A water-resistant layer installed between the roof deck and shingles. Modern installs use synthetic underlayment (lasts longer than felt). Ice and water shield (a self-adhering rubberized membrane) is installed in valleys and at eaves in cold climates.
Underpinning
Foundation repair method that transfers the home's weight through unstable surface soil down to stable bearing soil using piers. The standard fix for foundation settlement. Cost: $1,500-$3,000 per pier; typical project 4-12 piers.
See: Settling Foundation Repair Cost · Foundation Pier Installation Cost
V
Valley flashing
Sheet metal installed where two roof slopes meet (forming a "valley") to direct water flow. Aluminum or steel; lasts 30-50+ years if properly installed. Replacement during roof tear-off: $600-$1,500 per valley.
W
Wall anchor (foundation)
A foundation repair method using steel anchors driven through a basement wall to anchor plates buried in stable soil 10-12 feet outside the home. Gradually pulled tight to straighten bowed walls. Cost: $400-$700 per anchor; 5-12 anchors typically needed per wall.
Cost guides by service
Definitions reflect 2026 US construction and insurance industry usage. Regional terminology may vary. See methodology for sourcing.