Custom home building glossary

Also called ALR

A British Columbia land designation protecting agricultural capability. On ALR land, residential use is subordinate to farming: house size can be constrained, additional dwellings require Agricultural Land Commission approval, and subdivision is generally refused.

Where this trips people up. It covers most of Abbotsford and a large share of the Okanagan’s rural land. Confirm a parcel’s status before making an offer — this is the most common expensive assumption made by buyers new to those markets.

GreenbeltOak Ridges MoraineBuilding on ALR land →

The continuous layer in a wall, roof or floor assembly that stops air moving through it. Continuity matters more than material — every penetration is a leak unless deliberately sealed.

Where this trips people up. Airtightness is workmanship, not product. The pre-drywall walkthrough is the last moment you can see whether the penetrations were actually sealed.

Vapour barrierAir changes per hour at 50 PaThermal bridgeThe pre-drywall walkthrough →

Also called ACH50, Airtightness

A measure of building airtightness: how many times the interior volume of air leaks out per hour when the house is pressurised or depressurised to 50 pascals. Measured by blower-door test.

Where this trips people up. This is the number that makes "energy efficient" checkable. Ask a builder for blower-door results from houses they have already finished, not for an adjective.

Blower-door testAir barrierEffective R-valueEnvelope and performance →

A placeholder sum written into a building contract for an item that has not been selected yet — tile, plumbing fixtures, lighting, millwork. When the actual item is chosen, the difference is added to or credited against the contract price.

Where this trips people up. Allowances are the most common reason a custom home finishes above its contract price. A builder pricing competitively has an incentive to set them low, because a lower total wins the job and the overrun arrives later. Ask whether each figure is supply-only or supplied-and-installed — that distinction alone moves allowances substantially.

Change orderFixed-price contractContingencyAllowances and change orders →

Authorisation from the road authority for a new or altered driveway access onto a public road, typically covering the culvert and the apron where the driveway meets the road.

Private sewage system

A delivery model in which an independent architect retained by the client holds the design, and the builder is engaged to price and execute it.

Where this trips people up. Keeps design advocacy independent of the party performing the work. Strongest where the site is difficult, the brief unusual, or the detailing unforgiving.

Design-buildContract administrationWorking with an architect →

Also called Design guidelines, Restrictive covenant

Requirements registered on title or imposed by a developer governing design in a subdivision — minimum floor area, roof form, exterior materials, garage orientation, landscaping and completion deadlines.

Where this trips people up. Where registered on title they are enforceable, and the design review committee approves your drawings before the municipality sees them. That is a sequential dependency, not a parallel one, and it is the most commonly underestimated item in an estate-community schedule.

Heritage conservation districtDevelopment permitBuilding in a controlled estate community →

A British Columbia compliance path setting escalating energy performance requirements verified by energy modelling and airtightness testing, rather than by prescriptive assembly tables.

Where this trips people up. The required step varies by municipality and rises over time. Practically it means an energy advisor is on the team from schematic design rather than added at permit.

Blower-door testAir changes per hour at 50 PaNet Zero Ready

Solid rock beneath surface soil. Where shallow, excavation requires rock removal — hammering or blasting — which is a substantial and highly variable cost.

Where this trips people up. Common across southern Vancouver Island, the North Shore and much of Halifax Regional Municipality. Establish depth with a test pit before the offer conditions expire; it is the most common source of budget shock in those markets.

Geotechnical reportBuilding on a rock lot →

A test that pressurises or depressurises a house with a calibrated fan to measure how much air leaks through the envelope, producing an airtightness result.

Where this trips people up. Required before occupancy in jurisdictions using the BC Energy Step Code. Elsewhere it is optional, which makes a builder who tests voluntarily worth noticing.

Air changes per hour at 50 PaBC Energy Step Code

The approval authorising construction to begin, confirming the design meets the building code. Issued after any required land-use approval.

Development permitOccupancy permit

A written amendment to a building contract that alters scope, price or schedule after signing. Both parties sign it, and it should be priced before the work is performed rather than after.

Where this trips people up. A verbal change is the most common source of a dispute at possession. Every change order should state its schedule impact as well as its cost — a change that costs little and delays four weeks is not a small change.

AllowanceContingencyAllowances and change orders →

Testing, adjusting and documenting building systems so they operate as designed — measuring and balancing ventilation flows, verifying controls, and recording the result.

Where this trips people up. Ask for commissioning reports as a deliverable at possession. Equipment that was installed but never balanced is a common and invisible failure.

Heat recovery ventilatorDeficiency list

The municipal body in Ontario that hears minor variance and consent applications. Most genuinely custom designs in the GTA pass through it.

Where this trips people up. Applications are public and objections are common. Ask any prospective designer or builder what your local Committee has actually approved in the last twelve months, and treat a vague answer as informative.

VarianceOntario Land Tribunal

An Ontario watershed-based agency regulating development near watercourses, valleys, wetlands and hazard land. A permit is required within its regulated area.

Where this trips people up. On a valley-adjacent parcel the conservation authority’s regulated area, not the zoning bylaw, usually determines the building envelope. Check before an offer closes.

Riparian setbackFloodplainOak Ridges Moraine

Also called Builders lien, Mechanics lien

A statutory claim registered against a property’s title by a contractor, subcontractor, supplier or worker who has not been paid for work or materials supplied to that property.

Where this trips people up. It attaches to the improved land, not to the party who failed to pay — which means you can pay your builder in full and still face one. That is exactly what the statutory holdback exists to limit.

HoldbackStatutory declarationLiens and holdback →

Also called Draw mortgage

A loan that finances construction by advancing funds in stages against verified progress, then typically converts to a conventional mortgage at completion.

Where this trips people up. It works nothing like a purchase mortgage. Understand the draw schedule, the inspection trigger for each advance, who carries interest during construction, and how the holdback interacts with it — before signing the building contract, not at the second draw.

DrawHoldbackInterest during constructionDraw and financing planner →

A reserve held against unforeseen costs. The builder may carry one inside a fixed price; the owner should hold a separate one of their own and treat it as already spent.

Where this trips people up. A buyer without contingency ends up value-engineering the finishing package to pay for a foundation problem. Note also that unspent contingency inside a builder’s fixed price usually does not come back to you — ask.

AllowanceEscalation clause

An insulation layer outboard of the framing, uninterrupted by structural members, so nothing bridges through it.

Thermal bridgeEffective R-value

An architect’s involvement during construction: site reviews, answering queries, certifying draws, assessing whether work conforms to the documents, and close-out.

Where this trips people up. The phase most often cut from an architect’s scope, and the one that makes them your advocate during construction. Ask explicitly whether a fee includes it and how many site reviews.

Architect-ledDrawWorking with an architect →

A contract under which the owner pays documented actual costs plus a builder’s fee. Transparent and well suited to work with unknown existing conditions, because it handles uncertainty without requiring a fully defined scope.

Where this trips people up. Where the fee is a percentage of cost, a more expensive project pays the builder more. Prefer a fixed fee where you can negotiate it, and define precisely what counts as a cost versus what sits inside the fee — supervision, site vehicles, small tools and overhead are the usual grey areas.

Fixed-price contractGuaranteed maximum priceCost-plus vs. fixed price →

A home designed for a specific client and a specific site, as distinct from a production or semi-custom home adapted from a builder’s existing plan set.

Where this trips people up. Used generously. Many builders describe adapting a plan set as custom, which is a legitimate product but a different one. Ask how much of the portfolio is repeated plans.

Spec homeDesign-build

An amount retained under the building contract until the deficiency list is complete. It is contractual, and separate from the statutory lien holdback.

Where this trips people up. Buyers routinely conflate the two. They have different purposes, different sources and different release conditions, and both clocks have to run before all the money goes.

HoldbackDeficiency listDeficiencies and possession →

Also called Punch list, Snag list

The itemised record of incomplete or defective work identified at the pre-possession walkthrough, with a target date against each item.

Where this trips people up. It is a contractual document, not a note. Numbered, located, photographed, dated and acknowledged in writing — a verbal commitment at possession is the least reliable promise in the project.

Deficiency holdbackOccupancy permitDeficiencies and possession →

Municipal authorisation to remove an existing structure, generally requiring confirmed utility disconnects and, on older buildings, a hazardous materials survey.

Where this trips people up. In a heritage district a demolition permit may be refused. Establish the building’s heritage status before you buy a teardown.

Designated substance surveyHeritage conservation district

A delivery model in which the builder holds the design, either in-house or through a designer they engage, giving a single point of accountability for both design and construction.

Where this trips people up. The trade-off is that your design advocate and the party pricing the work are the same party. That is not a reason to avoid it; it is a reason to choose it deliberately.

Architect-ledContract administrationBuilder or architect first? →

An assessment identifying hazardous materials — most commonly asbestos, and lead in older finishes — before demolition or renovation, so they can be removed safely and lawfully.

Where this trips people up. Assume one is needed on any pre-1990 house. Discovering asbestos mid-demolition stops the job and costs far more than the survey would have.

Demolition permit

Also called Development charge, Off-site levy

A municipal charge on new development toward the cost of infrastructure serving it. Payable at permit and varying enormously between municipalities.

Soft costsBuilding permit

Also called DP

A land-use approval confirming a proposed development complies with the applicable planning rules. It is separate from and usually precedes a building permit.

Where this trips people up. Where a development permit is discretionary it is advertised, neighbours may object, and refusal or appeal can add many months. On an inner-city rebuild the approval, not the construction, is usually the schedule risk.

Building permitVarianceLand use bylaw

Also called Progress advance

A stage payment released by a construction lender after an inspection confirms a defined amount of work is in place. Construction mortgages advance in draws rather than as a single lump sum.

Where this trips people up. Because the advance follows the work, you carry the gap between money spent and money advanced. That gap plus the holdback is your peak cash requirement, and it usually peaks mid-build.

HoldbackConstruction mortgageDraw and financing planner →

Also called Right of way

A registered right allowing another party to use part of a property for a defined purpose — commonly utilities, drainage or access.

Where this trips people up. An easement across the middle of a parcel can eliminate the building envelope you had in mind. Check title during the conditional period.

Real Property ReportArchitectural controls

The thermal resistance an assembly actually achieves once thermal bridging through framing is accounted for, as opposed to the nominal rating of the insulation product alone.

Where this trips people up. The most common way an envelope claim misleads without anyone lying. Ask which figure a builder is quoting.

Thermal bridgeContinuous insulationEnvelope and performance →

A contract provision allowing the price to rise if material or labour costs increase beyond a defined threshold during construction.

Where this trips people up. On a two-year project this is a live risk rather than boilerplate. Ask what triggers it, whether it is capped, and whether it can operate without your written approval.

Fixed-price contractChange order

Soil that changes volume significantly with moisture — swelling when wet and shrinking when dry. The seasonal movement can damage conventional foundations, flatwork and finishes.

Where this trips people up. The defining structural condition in Winnipeg and Saskatoon, where piled foundations with void form are standard practice rather than an upgrade. Landscape irrigation practice after possession genuinely affects the foundation.

Piled foundationVoid formGeotechnical reportBuilding on expansive clay →

A Canadian programme of construction and landscape practices reducing wildfire risk — non-combustible cladding and roofing, enclosed soffits, ember-resistant vents and defensible space around the building.

Wildland-urban interface

Also called Stipulated sum, Lump sum

A contract setting one price for a defined scope of work. The builder carries the risk that the work costs more than estimated, and includes contingency for that risk in the price.

Where this trips people up. The certainty only covers the scope in the documents, and on a custom home the documents are rarely complete enough to define everything. Fixed-price custom contracts frequently finish above the contract price through allowances and change orders, without anyone acting dishonestly.

Cost-plus contractGuaranteed maximum priceAllowanceCost-plus vs. fixed price →

Also called FCL

The minimum elevation at which habitable floor space may be built on flood-prone land. Meeting it can require fill, a raised foundation, or a design that puts nothing of value at grade.

FloodplainBuilding on the Fraser Valley floor →

Land subject to flooding, mapped by the relevant authority. Development within it is restricted, and where permitted is typically subject to a flood construction level.

Where this trips people up. Flood mapping is public and specific to a parcel. On river-adjacent land in Calgary, Edmonton and the Fraser Valley it can determine what may be built at and below grade.

Flood construction levelConservation authority

Also called FAR, Floor space index, FSI

The ratio of a building’s total floor area to the area of the lot it sits on. A common zoning control on how much house a parcel can carry.

Where this trips people up. What counts toward the ratio varies by municipality — basements, garages and covered outdoor space are treated differently in different places. Confirm the local definition rather than assuming.

Land use bylawVariance

Also called Soils report

An engineer’s assessment of subsurface conditions — soil type, bearing capacity, water table, bedrock depth, slope stability — and what they mean for foundation design.

Where this trips people up. Inexpensive relative to what it prevents. On expansive clay, sensitive marine clay, steep slopes or suspected rock it is the highest-value item in a conditional period.

Expansive claySlope stability reviewBedrock

A reinforced concrete beam spanning between piles or piers at or near ground level, carrying wall loads to the piles rather than to the soil beneath it.

Piled foundationVoid form

An Ontario land protection framework restricting development across a defined area of countryside, farmland and natural systems around the Greater Golden Horseshoe.

Where this trips people up. A large rural parcel inside the Greenbelt is not automatically buildable. Confirm designation and permitted uses before you buy.

Oak Ridges MoraineConservation authority

The design snow load specified for a location, driving structural design of the roof and the framing beneath it.

Where this trips people up. Varies enormously across Canada. In Fernie and comparable mountain markets it is the defining engineering constraint, and a roof form that works on the prairies can be a liability there.

Snow sheddingBuilding under heavy snow load →

Goods and Services Tax applies to newly constructed housing in Canada. It does not apply to most resale housing, which makes build-versus-buy comparisons misleading if it is left out.

Where this trips people up. Ask explicitly whether a quoted price is GST-inclusive. Rebate provisions exist and depend on price thresholds and use — confirm the current rules with the Canada Revenue Agency or your accountant.

Soft costs

Also called GMP

Cost-plus with a ceiling. Costs are billed open-book as incurred, but the total is capped — below the cap the owner pays actual cost, and above it the builder absorbs the overrun.

Where this trips people up. Check that the ceiling is tight enough to constrain anything. A GMP set well above a realistic estimate is a fixed-price contract with extra paperwork. Negotiate savings sharing below the cap, or the builder has no reason not to spend to it.

Cost-plus contractFixed-price contractCost-plus vs. fixed price →

Also called HRV, ERV

A balanced mechanical ventilation unit that exhausts stale air and supplies fresh air while recovering heat from the outgoing stream. Standard in airtight Canadian construction.

Where this trips people up. Commissioning is the part that gets skipped. An uncommissioned unit with unbalanced flows is a box in the mechanical room, not a ventilation system — ask for the commissioning report.

Air changes per hour at 50 PaCommissioning

Also called HCD

An area designated for its heritage character, with published guidelines governing design, alteration and demolition within it.

Where this trips people up. Demolition of a contributing building may be refused outright. Establish a property’s status before making an offer — it determines whether your plan is possible at all, and it is public information.

Architectural controlsBuilding in a heritage district →

Also called Statutory holdback, Lien holdback

A percentage of each payment retained for a defined period under construction lien legislation. It is the fund unpaid subcontractors and suppliers can claim against, and it limits an owner’s exposure to paying twice.

Where this trips people up. The percentage and the period vary by province and several have changed with prompt-payment reform — confirm both with a construction lawyer rather than relying on a figure from a guide. Releasing early, as a favour, can forfeit the protection.

Construction lienDeficiency holdbackStatutory declarationLiens and holdback →

Interest accruing on the amounts advanced while the house is being built, before the loan converts to a conventional mortgage. It rises through the project as the outstanding balance grows.

Where this trips people up. It is not simply rate × total × time. Early draws accrue for longer than late ones, so the figure follows the actual balance rather than an average. Rarely in anyone’s first spreadsheet.

DrawConstruction mortgage

Also called Zoning bylaw

The municipal instrument setting what may be built on a parcel: permitted and discretionary uses, height, setbacks, site coverage and floor area.

Where this trips people up. On a constrained lot the bylaw envelope, not your brief, determines what fits. Get a rough massing study inside it before you buy rather than after.

VarianceDevelopment permitFloor area ratio

Also called Enclosure, Weather-tight

The stage at which a house is framed, roofed, and has windows and exterior doors installed, so the interior is protected from weather.

Where this trips people up. In cold markets, reaching lock-up before freeze-up is worth substantial money — it lets interior trades work through winter without hoarding and heating.

DrawGround snow load

A home built to a performance standard such that adding renewable generation would offset its annual energy consumption, without that generation being installed.

Where this trips people up. Certification buys third-party verification rather than performance in itself — the same standard can be built to without certifying. Worth it if you want independent confirmation.

BC Energy Step CodeAir changes per hour at 50 Pa

Mandatory coverage in most Canadian provinces protecting a new home’s buyer against defects, structured in tiers that lengthen for more fundamental components.

Where this trips people up. The framework, administrator, periods and builder licensing all differ by province. Confirm with the provider that YOUR address is enrolled — not merely that the builder holds an account.

Deficiency listHoldbackWarranty province by province →

A landform north of Toronto protected by its own conservation plan, which restricts development on designated land across York, Durham and Peel.

Where this trips people up. It covers a great deal of the attractive rural land north of the GTA. Together with conservation authority jurisdiction it governs most rural parcels there, and either can prevent development.

GreenbeltConservation authority

Municipal confirmation that a building is safe and lawful to occupy, issued after final inspections. Usually required before possession.

Building permitDeficiency list

Also called OLT

The provincial tribunal that hears appeals of Ontario planning decisions, including refused or contested minor variances.

Where this trips people up. An appeal can add a year or more. Budget carrying cost for the contested case even when you expect the uncontested one.

Committee of AdjustmentVariance

Also called Perc test

A soil test measuring how quickly water drains, used to determine what kind of private sewage system a parcel can support and where the field can go.

Where this trips people up. The result determines system type and cost, and the field location constrains house siting. Do not finalise a site plan before the sewage design is understood.

Private sewage systemWell yieldAcreage servicing →

A foundation transferring load through piles to stable ground below the zone of seasonal soil movement, rather than bearing on soil near the surface.

Expansive clayVoid formGrade beam

Also called Precon

A paid phase in which a builder is engaged during design to price the work and advise on constructability, before any construction contract is awarded.

Where this trips people up. Underused because it means paying a builder before awarding them the job. Usually the best money in the process — a constructability problem found during design costs a drawing revision; the same problem at tender costs a redesign.

Design-buildArchitect-led

Also called Septic system

On-site wastewater treatment and disposal for a parcel with no municipal sewer connection. Type and design follow from soil conditions and are set by a certified designer.

Where this trips people up. In Alberta these are designed and installed under the provincial Standard of Practice. System type — conventional field, mound, packaged treatment plant, holding tank — can differ several-fold in cost.

Percolation testWell yieldAcreage servicing estimator →

A naturally occurring radioactive gas that can accumulate indoors. The Alberta Building Code requires rough-in for a sub-slab depressurisation system in new homes.

Where this trips people up. Rough-in is not mitigation. Testing after occupancy is inexpensive and is the only way to know whether the system needs to be activated.

A wall assembly with a drained and vented cavity behind the cladding, so water that gets past the outer surface can drain away and the assembly can dry.

Where this trips people up. Standard practice on the BC coast, and the region’s response to the leaky-condo era. Ask any Lower Mainland or Vancouver Island builder to describe their assembly layer by layer.

Vapour barrierAir barrierBuilding on the wet coast →

Also called RPR, Survey

A legal survey document showing the location of improvements relative to property boundaries, commonly with a municipal compliance stamp.

Where this trips people up. Confirms what is actually where, which is not always what title or an old sketch suggests. Encroachments discovered late are expensive.

Easement

A required separation between development and a watercourse, protecting the stream and its bank. In British Columbia it is assessed under the Riparian Areas Protection Regulation.

Where this trips people up. A creek within the regulated distance can substantially constrain siting even on a large parcel.

Conservation authorityFloodplain

Assessment of whether ground near a slope or top of bank can safely support development. Typically requires a geotechnical report and can dictate setback, foundation design and buildable area.

Where this trips people up. The defining constraint on Edmonton river-valley lots and on steep North Shore and Okanagan hillside parcels. Resolve it as a condition of purchase, not after.

Geotechnical reportTop of bankBuilding near a river valley →

How and where snow slides off a roof. A design consideration in heavy-snow markets, because shed snow has to land somewhere safe.

Where this trips people up. Shedding onto an entrance, a deck, a mechanical vent or a neighbour’s property is a real and common design failure. Ask where the snow goes.

Ground snow load

Project costs that are not construction labour or materials: design and engineering fees, permits and levies, consultants, financing costs, legal fees and insurance.

Where this trips people up. Soft costs are real costs and are almost never inside a builder’s per-square-foot rate. Budget them as their own line rather than assuming they are covered.

GST on new housingDevelopment levy

Also called Quick possession, Standing inventory

A home a builder constructs on their own initiative to sell on completion, rather than for a specific client. The opposite of custom, and a different product entirely.

Custom home

A sworn statement from a builder confirming that subcontractors and suppliers have been paid to a given date. Commonly required at each draw.

Where this trips people up. It does not guarantee no liens, but it converts non-payment from an oversight into a documented misrepresentation. A builder who resists providing one is telling you something.

Construction lienHoldbackDraw

A path of higher heat conduction through an assembly — typically framing, headers, plates and rim joists — that bypasses the insulation between them.

Where this trips people up. Thermal bridging is why a wall’s effective R-value is meaningfully lower than the insulation’s nominal rating. Continuous exterior insulation is the usual response.

Effective R-valueContinuous insulation

The upper edge of a valley or ravine slope. Setbacks are commonly measured from it rather than from the property line.

Slope stability reviewRiparian setback

Also called Vapour retarder

A layer controlling moisture diffusion through an assembly. Distinct from an air barrier, which controls air movement — the two are often the same material but they do different jobs.

Where this trips people up. In climates with hot humid summers and cold winters the vapour drive reverses seasonally. A wall detailed for one direction only can trap moisture.

Air barrierRainscreen

Also called Minor variance, Relaxation

Permission to depart from a specific zoning requirement — height, setback, coverage — where the departure is considered minor and consistent with the intent of the by-law.

Where this trips people up. Routine in some markets and contested in others. In the GTA a minor variance goes to the Committee of Adjustment, is public, and can be appealed to the Ontario Land Tribunal, which adds substantial carrying cost on expensive land.

Committee of AdjustmentDevelopment permitLand use bylaw

A collapsible material placed beneath grade beams to create a gap, giving expansive soil somewhere to swell without lifting the structure above it.

Piled foundationExpansive clayGrade beam

The sustained rate at which a drilled well produces water, usually expressed in gallons per minute. It determines whether a well can serve a given house.

Where this trips people up. Not predictable from a neighbour’s well. On a bare parcel it is not knowable until someone drills, which is why the honest estimate is a range and why water is the first question on any acreage purchase.

Private sewage systemPercolation testAcreage servicing estimator →

Also called WUI, Wildfire interface

The zone where development meets wildland vegetation, carrying elevated wildfire risk. It influences material choice, landscape design and, increasingly, insurance.

Where this trips people up. Across much of the BC interior this has become an insurance question as well as a design one. Establish coverage and premium for a specific parcel before committing.

FireSmart