Excavation Services for House Extension
Excavation Chanthier: Experts in House Extension
Are you planning to expand your house? Excavation Chanthier is your ideal partner for precise and efficient excavation services. We cover all your needs for expansion projects, guaranteeing solid foundations and carefully prepared land.
Our company has the RBQ license, a quality guarantee, and can operate in the following sectors: Longueuil, Greater Montreal, the North Shore of Montreal, Laval, Repentigny, Lanaudière.
Our Excavation Services for House Extension
Site Preparation: We prepare your land for expansion by ensuring precise excavation, creating a stable base for your new constructions.
Foundations: Solid foundations installation, adapted to the specificities of your expansion project, guaranteeing a durable structure.
Debris Management: Debris removal and site cleaning after excavation, ensuring a space ready for construction.
Why Choose Excavation Chanthier?
Expertise and Precision: Our experienced team uses advanced techniques for impeccable results.
Safety and Reliability: We respect all safety standards, ensuring work without risk for you and your property.
Personalized Service: Solutions adapted to each project, specifically meeting your needs.
For a successful home extension, trust Excavation Chanthier. Contact us today for a free consultation and a personalized quote. We serve Greater Montreal, including the South and North Shores.
House Extension Excavation Montreal - FAQ Guide
Planning a house extension in Greater Montreal? Excavation is the critical first step that determines your project’s success. These frequently asked questions address the most common concerns homeowners have about house extension excavation costs, permits, contractors, and foundation requirements.
Quick FAQ Summary
Is this excavation quote too high or reasonable?
Do I need a structural engineer for my house extension?
What permits do I need for excavation and house extension?
How do I find a qualified excavation contractor?
Can my existing foundation support a house extension?
Is this excavation quote too high or reasonable?
This is the most common question in Montreal homeowner forums—and for good reason. House extension excavation represents one of the largest single costs in any addition or basement expansion project. Unfortunately, there’s significant quote variation across contractors, making it difficult to know if you’re getting fair pricing or being overcharged.
Current Montreal excavation pricing (2024-2025):
| Excavation Type | Average Cost | Cost Range | Typical Volume |
|---|---|---|---|
| Basic excavation (per m³) | $125-$200/m³ | Low complexity, easy access | – |
| Complex excavation (per m³) | $250-$500/m³ | Difficult access, clay soil, tight spaces, shoring required | – |
| Full basement excavation | $60,000-$120,000 | Includes excavation, foundation work, waterproofing, backfill | 100-200 m³ |
| Basement underpinning | $60,000-$100,000+ | Lowering existing basement floor depth | Specialized work |
| Crawl space to basement conversion | $80,000-$150,000 | Includes underpinning, new foundation walls, waterproofing | 50-100 m³ |
What’s included in a complete house extension excavation quote:
A properly detailed quote should itemize these costs separately:
1. Site preparation and demolition:
- Removing existing structures, decks, patios
- Tree and shrub removal if necessary
- Relocating utilities (hydro, gas, water, telecommunications)
- Typical cost: $5,000-$15,000
2. Excavation work:
- Actual earth removal (priced per cubic meter)
- Shoring and temporary supports if required
- Protection of adjacent structures
- Typical cost: $125-$500/m³ depending on complexity
3. Soil disposal and trucking:
- Loading excavated material
- Trucking to approved disposal sites
- Disposal/dumping fees
- Typical cost: $40-$80/m³
4. Foundation work:
- Formwork installation
- Rebar placement and tying
- Concrete pouring (footings and walls)
- Foundation waterproofing and drainage membrane
- Weeping tile (French drain) installation
- Typical cost: $30,000-$60,000 for standard basement
5. Backfilling and grading:
- Compacted backfill around new foundation
- Final grading to ensure proper drainage away from house
- Typical cost: $3,000-$8,000
6. Site restoration:
- Topsoil replacement
- Seeding or sodding
- Driveway or walkway repairs
- Typical cost: $2,000-$6,000
Major cost variables that affect your house extension excavation quote:
1. Soil type:
Clay soil: Montreal’s infamous clay soil significantly increases excavation difficulty and cost. Clay is heavy, sticky, requires proper shoring to prevent cave-ins, and is expensive to dispose of. Expect +30-50% cost increase.
Rocky soil: Bedrock or significant rock content requires hydraulic breakers or rock saws. Can increase costs by +50-100% or more.
Sandy/gravel soil: Easiest to excavate but requires additional shoring and drainage considerations. Near baseline cost.
2. Site access:
Backyard excavation with no direct access: Requires smaller equipment, hand digging, or conveyor systems to remove soil over/around house. Can increase costs by +40-60%.
Narrow lot or tight spaces: Limited equipment maneuverability increases labor hours. Expect +20-35% cost increase.
Direct street access with large equipment: Most efficient scenario. Baseline cost.
3. Excavation depth:
Shallow excavation (under 1.2m): Minimal shoring requirements. Lower cost.
Standard basement depth (2.0-2.4m): Requires proper shoring and safety measures. Standard pricing applies.
Deep excavation (over 2.4m): Requires engineered shoring systems, additional safety measures, and specialized equipment. Increases cost by +25-40%.
4. Existing foundation condition:
New construction or extension only: No existing foundation complications. Baseline cost.
Underpinning required: Excavating beneath existing foundations while keeping house stable. Major cost increase of $60,000-$100,000+ as standalone cost.
Foundation repairs needed before excavation: Cracks, water infiltration, or structural issues must be addressed first. Variable costs: $10,000-$50,000+.
5. Utility complications:
No utilities in excavation area: Baseline cost.
Utilities requiring temporary relocation: Hydro, gas, water, or telecommunications lines in excavation path. Utility company involvement, temporary disconnections, and reconnections required. Can add $3,000-$15,000 to project.
Major utility conflicts requiring permanent relocation: Can add $10,000-$30,000+ depending on complexity.
Example: Real Montreal house extension excavation cost breakdown
Project: 800 sq ft (74 m²) basement excavation under existing single-storey house in Laval
Soil type: Montreal clay
Access: Backyard only, narrow side yard passage
Depth: 2.2m (standard basement)
Foundation: Underpinning required (existing shallow footings)
Complete cost breakdown:
- Excavation (120 m³ @ $280/m³): $33,600
- Soil disposal (120 m³ @ $65/m³): $7,800
- Underpinning work: $78,000
- New foundation walls and footings: $42,000
- Waterproofing and drainage: $8,500
- Backfill and grading: $5,200
- Site restoration: $3,800
- Utility temporary relocation: $4,200
- Engineering and permits: $6,500
Total project cost: $189,600
Key insight: Notice that actual excavation ($33,600) represents only 18% of total project cost. The underpinning, foundation work, and associated costs dominate the budget. This is typical for Montreal basement extensions.
Red flags that indicate an unreliable or inflated house extension excavation quote:
- Single lump sum with no itemization: Legitimate contractors provide detailed breakdowns showing excavation, disposal, foundation work, materials, and other costs separately.
- Price significantly below market (more than 30% lower): Either the contractor doesn’t understand the scope, plans to cut corners, or will hit you with change orders later.
- Verbal estimate only: All legitimate quotes should be in writing with detailed specifications and exclusions.
- No mention of permits or engineering: These are mandatory for house extension excavation. If the quote doesn’t include them, costs will appear artificially low.
- Unusually high upfront deposit requested (more than 15%): Standard practice in Quebec is 10-15% deposit maximum. Higher requests are red flags for financial instability or fraud.
- No RBQ license verification offered: Every excavation contractor must hold valid RBQ licensing (categories 2.4 or 2.5). If they resist providing license numbers, walk away.
- Pressure to sign immediately: Legitimate contractors understand you need time to compare quotes and make informed decisions.
How to properly compare multiple house extension excavation quotes:
Step 1: Ensure identical scope across all quotes. Each contractor should quote the same specifications: excavation depth, foundation design, waterproofing type, drainage specifications, backfill requirements, and site restoration expectations.
Step 2: Compare itemized costs individually. Don’t just look at total price. Compare excavation rate per m³, disposal costs, foundation costs, and other line items separately. This reveals where contractors differ in approach or pricing.
Step 3: Verify what’s included vs. excluded. Some quotes exclude permits, engineering, utility relocations, or site restoration. Identify all exclusions and get supplementary quotes for excluded items to calculate true total cost.
Step 4: Assess quality differences. Lower quotes might use thinner foundation walls, cheaper waterproofing, or less robust drainage systems. Verify specifications match Code minimums or exceed them.
Step 5: Check contractor qualifications and insurance. Get copies of:
- Current RBQ license (categories 2.4 or 2.5 required)
- $2 million minimum liability insurance certificate
- CNESST confirmation (if hiring workers)
- References from 3+ similar Montreal projects completed within past 2 years
Step 6: Understand payment terms. Standard structure is: 10-15% deposit, 25-30% at excavation completion, 25-30% at foundation completion, 25-30% at final completion with 10% holdback for deficiencies (released 30 days after completion).
Important consideration: The cheapest quote is rarely the best value. Montreal’s clay soil, older housing stock, and strict Code requirements make house extension excavation technically demanding. Choose contractors based on:
- 40% – Technical competence and experience with similar projects
- 30% – Detailed specifications and thoroughness of quote
- 20% – Price competitiveness within reasonable market range
- 10% – Communication quality and professionalism
Do I need a structural engineer for my house extension?
Short answer: Yes, it’s mandatory for permit approval in Quebec.
This question appears repeatedly in Montreal homeowner forums, often from people hoping to save $3,000-$8,000 in engineering fees. The reality: structural engineering is not optional for house extension excavation projects. Quebec’s Construction Code and municipal bylaws require professional engineering stamps for any work involving foundations or structural modifications.
When structural engineering is legally required for house extension excavation:
Quebec Construction Code Chapter I, Building (2020 edition) requires professional engineering for:
- All foundation designs: New foundations, foundation extensions, or foundation modifications must be designed and sealed by a licensed structural engineer (Ordre des ingénieurs du Québec – OIQ member).
- Underpinning or foundation reinforcement: Any work that involves excavating beneath existing foundations or altering load-bearing capacity.
- Load-bearing wall modifications: Removing or altering walls that support upper floors or roofs.
- Second-storey additions: Evaluating whether existing foundations can support additional load.
- Structural connections: Connecting new extensions to existing structures.
Bottom line: If your house extension involves any excavation work that affects or interacts with your foundation, you need a structural engineer. No exceptions.
What a structural engineer does for your house extension excavation project:
Phase 1: Initial assessment and feasibility ($1,500-$3,000)
The engineer visits your property to:
- Inspect existing foundation condition (cracks, settling, water damage)
- Evaluate soil type and drainage conditions
- Review proposed extension plans with you
- Identify major concerns or deal-breakers (inadequate foundation, severe settling, soil problems)
- Provide preliminary feasibility assessment
- Recommend soil testing if required
Deliverable: Written feasibility report outlining major concerns, recommended approach, and preliminary cost implications for foundation work.
Phase 2: Detailed design and specifications ($3,000-$8,000)
If project proceeds, engineer produces:
- Foundation design drawings: Detailed plans showing footing dimensions, depths, reinforcement specifications, foundation wall thickness, and construction details
- Structural calculations: Load analysis proving foundation capacity meets Code requirements with safety factors
- Specifications document: Concrete strength requirements (typically 30 MPa minimum), reinforcement specifications (rebar sizing and spacing), waterproofing requirements, drainage specifications (weeping tile details)
- Shoring requirements: If excavating near existing structures, engineer designs temporary shoring systems to prevent collapse
- Professional seal and stamp: All drawings and calculations bear engineer’s seal, making them legally binding documents for permit applications
Deliverable: Complete construction document package ready for permit submission and contractor bidding.
Phase 3: Construction oversight (optional but recommended: $1,500-$3,000)
Many engineers offer site visit packages during construction:
- Foundation inspection before concrete pour (verifying formwork, rebar placement, depth)
- Mid-construction progress inspections
- Final inspection and sign-off for occupancy permit
Deliverable: Site inspection reports documenting compliance with design specifications, plus final certification letter for occupancy permit application.
Cost range for structural engineering services (Montreal 2024-2025):
| Service Type | Typical Cost | What You Get |
|---|---|---|
| Basic foundation design | $3,000-$5,000 | Simple extension, no complications, standard soil conditions |
| Complex foundation design | $5,000-$8,000 | Underpinning required, challenging soil conditions, or complex structural connections |
| Soil testing | $1,500-$3,000 | Geotechnical analysis by soil testing laboratory (separate from structural engineer) |
| Site inspection services | $500-$800 per visit | Engineer site visits during construction for compliance verification |
| Second-storey addition evaluation | $4,000-$8,000 | Comprehensive structural assessment of existing foundation’s capacity for additional load |
Why you can’t skip the structural engineer (beyond legal requirements):
1. Permit denial without engineering stamps:
Montreal, Laval, and all Greater Montreal municipalities will refuse permit applications lacking professional engineering documents. No stamp = no permit = illegal construction.
2. Insurance implications:
Your homeowner’s insurance may refuse claims related to unpermitted or improperly engineered work. If foundation failure occurs, you’re personally liable for all damages and repairs.
3. Resale complications:
Future buyers’ mortgage lenders scrutinize house additions. Unpermitted or inadequately documented work triggers red flags, potentially killing deals or forcing you to obtain retroactive permits (expensive and sometimes impossible).
4. Catastrophic failure risk:
Montreal’s clay soil and freeze-thaw cycles create unique foundation challenges. Undersized footings, inadequate depth, improper reinforcement, or poor drainage can lead to:
- Foundation heaving or settling
- Structural wall cracks
- Chronic water infiltration
- Complete foundation failure requiring emergency repairs ($50,000-$150,000+)
5. Code compliance assurance:
Quebec’s Construction Code is complex and constantly updated. Structural engineers remain current with:
- Frost depth requirements (minimum 1.5m in Montreal region)
- Concrete strength specifications for our climate
- Waterproofing standards for clay soil conditions
- Seismic considerations (Quebec is seismically active)
- Snow load calculations for roof structures
How to find a qualified structural engineer for house extension excavation:
Step 1: Verify OIQ membership.
All structural engineers in Quebec must be members of the Ordre des ingénieurs du Québec (OIQ). Verify membership at: oiq.qc.ca (public registry search).
Step 2: Look for residential specialization.
Not all structural engineers work on residential projects. Look for engineers with:
- Specific residential foundation design experience
- Familiarity with Montreal clay soil conditions
- Experience with underpinning and foundation rehabilitation
- Knowledge of local municipal requirements
Step 3: Ask for references.
Request contact information for 3-5 recent residential clients with similar projects (house extensions, basement excavations, or underpinning work). Verify:
- Project was completed successfully
- Permits were obtained without issues
- Construction proceeded smoothly following engineer’s designs
- Engineer was responsive during construction if site visits were included
Step 4: Get clear fee structure.
Request detailed proposal outlining:
- Scope of services included
- Timeline for deliverables
- Fee structure (fixed price or hourly rate)
- What’s excluded (site visits, revisions, additional services)
- Payment schedule
Step 5: Review deliverables commitment.
Ensure engineer commits to providing:
- Signed and sealed foundation drawings
- Structural calculations
- Specifications document
- Letter of compliance or certification for permit submission
When to hire your structural engineer (project timeline):
Timing is critical for efficient project flow:
Ideal timeline:
- Planning phase: Hire engineer BEFORE finalizing architectural plans. Engineers can identify structural impossibilities or expensive complications early, saving design revision costs.
- Design development: Engineer works alongside architect (if you’re using one) to ensure architectural vision is structurally feasible and economical.
- Pre-bidding: Complete engineering documents BEFORE requesting contractor quotes. Contractors need detailed foundation specifications to provide accurate pricing.
- Permit application: Submit complete engineering package with permit application. Missing or incomplete engineering causes permit delays (weeks or months).
- Construction phase: If including site inspection services, engineer visits at key milestones: foundation excavation completion, pre-concrete pour inspection, and final inspection.
Common mistake: Hiring engineer too late in the process. Some homeowners finalize architectural plans, get contractor quotes, then discover the structural engineer requires expensive foundation work that wasn’t budgeted. This creates costly redesigns or forces project cancellation.
Pro tip from Montreal contractors: The $3,000-$8,000 you spend on structural engineering typically saves you $10,000-$30,000 in construction costs. How? Engineers optimize foundation designs for your specific conditions—preventing over-building (wasting money on unnecessarily robust foundations) and under-building (causing failure). They also prevent permit delays and rejected inspections that halt construction and rack up contractor standby charges.
What permits do I need for excavation and house extension?
Permit requirements for house extension excavation in the Greater Montreal area are strict, municipality-specific, and absolutely mandatory. Working without proper permits results in stop-work orders, fines up to $20,000, forced demolition of unpermitted work, and permanent records on your property title that complicate future sales.
Core permits required for house extension excavation (all municipalities):
1. Transformation permit (Permis de transformation):
Required for any structural modification to your house, including:
- Adding square footage (extensions)
- Basement excavation or expansion
- Foundation work
- Second-storey additions
- Structural wall modifications
2. Excavation permit (Permis d’excavation):
Separate permit specifically for earthwork and excavation activities. Required for:
- Excavation deeper than 0.5m (typical municipal threshold)
- Excavation within 1.5m of property lines
- Any excavation requiring shoring or support systems
Note: Some municipalities combine these into a single permit; others require separate applications. See municipality-specific details below.
Municipality-specific permit requirements and costs:
| Municipality | Permit Type | Base Cost | Processing Time | Special Requirements |
|---|---|---|---|---|
| Montreal | Transformation permit + Excavation permit (separate applications) | $265 minimum + $9.80 per $1,000 of work value (minimum $161) | 4-6 weeks (longer if Public Consultation required) | PIIA approval required for heritage areas, Front yard setback restrictions apply |
| Laval | Combined construction permit (includes excavation) | $290 base + $11 per $1,000 of work value | 4-6 weeks | Site plan required, Compliance with specific zoning bylaws |
| Longueuil | Transformation permit + Excavation authorization | $350 base + variable based on project scope | 3-5 weeks | Archaeological assessment if in designated zone |
| West Island municipalities (DDO, Beaconsfield, Pointe-Claire, etc.) | Construction permit (includes excavation) | $300-500 base + percentage of construction value | 3-4 weeks | Often stricter setback requirements, Tree preservation bylaws may apply |
| North Shore municipalities (Rosemère, Blainville, Boisbriand, etc.) | Construction permit + Excavation permit | $250-400 + percentage calculation | 3-5 weeks | Environmental protection zones common, Stricter drainage requirements |
| South Shore municipalities (Brossard, Saint-Hubert, Candiac, etc.) | Combined renovation/construction permit | $300-450 + project value percentage | 4-6 weeks | Wetland protection regulations, Flood zone considerations |
Important: Permit costs shown are base municipal fees only. Your total permit costs will include:
- Municipality fees (as shown in table)
- Régie du bâtiment du Québec (RBQ) fees if required
- Professional fees for permit application preparation by architect or engineer
- Potential revision fees if initial application is incomplete or rejected
Required documentation for permit applications (comprehensive checklist):
Mandatory documents for all municipalities:
1. Completed permit application form
- Municipality-specific form (download from municipal website)
- Property owner information and authorization
- Contractor information (RBQ license number required)
- Estimated construction value
2. Site plan (Plan d’implantation)
- Drawn to scale (typically 1:100 or 1:200)
- Property boundaries and dimensions
- Existing structures with dimensions
- Proposed extension location and dimensions
- Setbacks from property lines (front, side, rear)
- Existing and proposed grading/drainage
- Location of utilities (water, sewer, electrical, gas)
- Driveway and walkway locations
3. Architectural drawings
- Floor plans showing existing and proposed layout
- Elevations (all sides of house showing extension)
- Cross-sections showing relationship to existing structure
- Construction details and specifications
- Dimensions and room labels
- Window and door schedules
4. Structural engineering drawings (MANDATORY)
- Foundation design drawings with footing details
- Structural calculations (load analysis)
- Specifications for concrete strength, reinforcement, waterproofing
- Engineer’s seal and signature on all pages
- Engineer’s OIQ membership number
5. Certificate of Location (Certificat de localisation)
- Recent survey by licensed land surveyor
- Shows existing structures, property lines, easements
- Must be dated within 10 years (some municipalities require more recent)
- If unavailable, new survey required ($1,500-$3,000)
6. Contractor licenses and insurance
- RBQ license certificate (categories 2.4 or 2.5 for excavation)
- Proof of liability insurance ($2 million minimum)
- CNESST confirmation if hiring workers
Special circumstances requiring additional approvals:
1. Heritage areas or PIIA zones (Montreal):
If your property is in a heritage district or Plan d’implantation et d’intégration architecturale (PIIA) zone, you need additional approval from the Comité consultatif d’urbanisme (CCU). This process:
- Adds 4-8 weeks to timeline
- May require public consultation
- Restricts exterior design choices to maintain neighborhood character
- Can result in design modifications or denials
2. Neighboring property considerations:
If excavating within 3 meters of property line or neighbor’s foundation:
- Notification required: Must formally notify adjacent property owners
- Neighbor consent: Some municipalities require written consent from affected neighbors
- Pre-construction survey: Document existing condition of neighbor’s property to protect yourself from false claims
3. Environmental considerations:
Wetlands or waterways: If your property is near wetlands, streams, or within flood zones, expect:
- Environmental impact assessment requirements
- Provincial permits from Ministère de l’Environnement
- Extended timelines (add 8-12 weeks)
Protected trees: Many municipalities have tree protection bylaws. Removing trees may require:
- Separate tree removal permit
- Compensation (planting replacement trees or paying fees)
- Arborist assessment in some cases
4. Servitudes (easements) on your property:
Check your property deed for easements (utility corridors, drainage, access rights). Construction in easement zones requires:
- Authorization from easement holder (utility company, municipality, or neighbor)
- Possible relocation of utilities
- Additional approvals and delays
Critical requirement: Info-Excavation call (mandatory 3 days before digging):
What is Info-Excavation?
Info-Excavation is Quebec’s mandatory one-call utility locate service. Before ANY excavation work begins—even minor digging—you or your contractor MUST call Info-Excavation at least 3 business days in advance.
Why it’s critical:
- Legal requirement: Provincial law (Loi sur le bâtiment) requires the call. Failure results in fines and personal liability.
- Safety: Prevents strikes on buried utilities (gas, electrical, water, telecommunications). Hitting a gas line can cause explosions; electrical lines can kill.
- Financial protection: If you call Info-Excavation and follow marked utility locations, you’re protected from liability for utility damage. If you don’t call, you’re personally responsible for repair costs (can exceed $50,000 for major utility damage).
How it works:
- Call 1-800-663-9228 or visit info-ex.com at least 3 business days before excavation start date
- Provide your address and describe excavation location and scope
- Receive confirmation number (keep this—inspectors will ask for it)
- Wait for utility companies to mark underground lines with colored flags or paint:
- Red = Electric
- Orange = Telecommunications
- Yellow = Gas
- Blue = Water
- Green = Sewer
- Excavate carefully around marked utilities. Use hand digging within 1 meter of marks.
Cost: FREE (funded by utility companies)
Validity period: Marks are valid for 30 days. If construction extends beyond 30 days, you must call again for re-marking.
Permit application timeline (realistic expectations):
Standard timeline for straightforward projects:
- Application submission: Day 0
- Initial review: 1-2 weeks (checking completeness of application)
- Technical review: 2-3 weeks (verifying Code compliance, reviewing engineering)
- Inspector questions/clarifications: 1-2 weeks (back-and-forth if issues identified)
- Permit issuance: 4-6 weeks total from submission
Extended timeline scenarios:
- Incomplete application: Add 2-4 weeks for revisions and resubmission
- Heritage area/PIIA review: Add 4-8 weeks for CCU review and possible public consultation
- Environmental approvals needed: Add 8-12 weeks for provincial permits
- Neighboring property disputes: Variable delays (can stall projects for months)
Pro tip: Submit permit applications in fall or winter. Spring and summer are peak construction seasons, causing permit office backlogs and longer processing times.
Permit inspections during construction:
Once construction begins, you’ll need municipal inspections at key milestones. Failing inspections halts work until issues are corrected.
Required inspection stages for house extension excavation:
1. Excavation inspection (before concrete pour):
- Inspector verifies excavation depth matches approved plans
- Checks footing dimensions
- Ensures proper compacted base
- Verifies shoring if required
- Must PASS before pouring concrete footings
2. Foundation formwork and rebar inspection (before concrete pour):
- Inspector checks formwork alignment and bracing
- Verifies rebar sizing, spacing, and placement per engineer’s drawings
- Confirms adequate rebar coverage
- Checks weeping tile and drainage installations
- Must PASS before pouring foundation walls
3. Waterproofing inspection:
- Verifies proper waterproofing membrane application
- Checks drainage board installation
- Confirms weeping tile connections
4. Backfill inspection:
- Ensures proper compaction
- Verifies grading slopes away from foundation
- Checks final site conditions
5. Final inspection:
- Overall project compliance with approved plans
- Safety verification
- Required before occupancy
How to request inspections:
Your contractor typically handles inspection requests, but as property owner, you should:
- Request inspections at least 48 hours in advance
- Be present during inspections if possible
- Get copies of inspection reports
- Understand that failed inspections mean work stops until corrections are made and re-inspection passes
Consequences of unpermitted house extension excavation work:
Many homeowners are tempted to skip permits to save money and time. This is extremely risky in Quebec:
Legal consequences:
- Stop-work orders: Municipality can halt construction immediately upon discovery
- Fines: $500-$20,000+ depending on municipality and violation severity
- Court orders: You may be ordered to obtain permits retroactively or demolish unpermitted work
- Criminal charges: In extreme cases involving safety violations
Financial consequences:
- Insurance voidance: Homeowner’s insurance may deny claims related to unpermitted work
- Resale complications: Buyers’ lenders often refuse mortgages on properties with unpermitted additions. You may be forced to:
- Obtain retroactive permits (expensive, sometimes impossible if work doesn’t meet current Code)
- Demolish unpermitted work
- Accept significantly reduced sale price
- Lose the sale entirely
- Demolition costs: If work cannot be brought into compliance, you’ll pay to demolish it PLUS original construction costs = total loss
Safety and liability consequences:
- No engineering oversight: Unpermitted work lacks professional engineering, increasing failure risk
- No inspections: Critical construction errors go undetected until catastrophic failure
- Personal injury liability: If unpermitted work causes injuries (collapse, fire, etc.), you’re personally liable with no insurance coverage
Reality check from Montreal lawyers: The $3,000-$5,000 you “save” by skipping permits can turn into $50,000-$150,000 in losses when problems arise. Permits aren’t optional red tape—they’re legal requirements protecting your investment and everyone’s safety.
How do I find a qualified excavation contractor?
This question reveals homeowners’ biggest fear: hiring an incompetent or fraudulent contractor who ruins their project. The Montreal area has excellent excavation contractors, but also has operators who lack proper licensing, cut corners on safety, or disappear mid-project. The cost of hiring the wrong contractor can exceed $100,000 in corrective work, legal fees, and project delays.
Absolute minimum qualifications (non-negotiable):
1. Valid RBQ license:
Category requirements for excavation work:
- Category 2.4 (Excavation et terrassement): Earth excavation, grading, backfilling
- Category 2.5 (Entrepreneur en fondations): Foundation construction
Verify licenses yourself:
- Visit: pes.rbq.gouv.qc.ca
- Search by company name or license number
- Verify license is active (not suspended or revoked)
- Check license categories match your project scope
- Verify authorized representative signing your contract holds the license
Red flag: Contractor refuses to provide RBQ license number or claims they “work under someone else’s license.” This is illegal. Only licensed contractors can perform or contract for work in their categories.
2. Adequate liability insurance:
Minimum coverage required:
- $2 million general liability insurance
- Request Certificate of Insurance (COI) naming you as additional insured
- Call insurance company directly to verify coverage is active
- Verify coverage includes excavation and foundation work specifically
Why this matters: If contractor damages your property, neighbor’s property, or utilities, adequate insurance protects you from personal liability. Without it, you’re personally responsible for damages even though you didn’t cause them.
3. CNESST registration (if hiring workers):
If contractor employs workers, they must be registered with Commission des normes, de l’équité, de la santé et de la sécurité du travail (CNESST). Request:
- CNESST registration number
- Confirmation that worker’s compensation premiums are current
Why this matters: Without CNESST coverage, if a worker is injured on your property, you may be held financially responsible for their medical costs, lost wages, and disability benefits.
How to evaluate contractor qualifications beyond basic licensing:
1. Experience with similar projects:
Not all excavation contractors have experience with house extension excavation. Specifically ask:
- “How many residential basement excavations have you completed in the past 2 years?”
- “Have you done projects involving underpinning or foundation work on occupied houses?”
- “Do you have experience with Montreal’s clay soil conditions?”
- “Can you provide references from similar projects?”
Ideal answer: Contractor regularly performs residential excavation in Montreal area, has specific underpinning experience if your project requires it, and can provide 3-5 references from projects completed within past 2 years.
2. Equipment ownership vs. rental:
Ask what equipment contractor owns vs. rents. Contractors who own excavation equipment typically:
- Have more experience and stability
- Can respond quickly if issues arise
- Have lower overhead (not paying daily rental fees)
- Are more likely to be full-time professional excavation companies
Note: Specialized equipment rental is normal (rock breakers, large cranes, etc.). But if contractor doesn’t own basic excavators and dump trucks, question their experience level.
3. Direct employees vs. subcontractors:
Ask if excavation work will be performed by contractor’s employees or subcontractors. Key considerations:
- Direct employees: Better quality control, direct supervision, clearer accountability
- Subcontractors: Can be excellent, but adds complexity. Verify subcontractors also have proper licenses and insurance
Red flag: General contractor with no excavation license hiring unlicensed “subcontractors.” This is illegal circumvention of licensing requirements.
4. Safety record and practices:
Ask about contractor’s safety program:
- “Do you have a written safety program?”
- “What safety training do your workers receive?”
- “Have you had any serious incidents or CNESST complaints?”
- “How do you handle shoring and cave-in prevention?”
Ideal answer: Contractor takes safety seriously with documented programs, regular training, and no significant incident history. House extension excavation involves serious cave-in risks—contractor must demonstrate competence in shoring and excavation safety.
Reference checking (the right way):
Request 3-5 references from projects completed within past 2 years. Older references may not reflect current quality or business practices.
Questions to ask references:
Project execution:
- “Did contractor complete project on time? If delayed, what were reasons and how was it handled?”
- “Was final cost close to original quote? If not, were change orders justified and documented?”
- “How was contractor’s communication during project? Responsive to questions and concerns?”
- “Did contractor’s crew show up consistently and work full days?”
Quality and professionalism:
- “Are you satisfied with quality of excavation and foundation work?”
- “Have you experienced any issues since completion (water infiltration, settling, cracks)?”
- “How did contractor handle site cleanliness and debris removal?”
- “Did contractor respect your property and minimize disruption?”
Problem resolution:
- “Were there any problems during construction? How did contractor handle them?”
- “Did contractor fix any deficiencies promptly?”
- “Would you hire this contractor again?”
- “Any advice or cautions based on your experience?”
Warning signs in reference responses:
- Hesitation or reluctance to recommend
- Mentions of unresolved deficiencies or ongoing problems
- Communication difficulties or unresponsiveness
- Significant cost overruns without clear justification
- Major delays without reasonable explanations
Red flags that indicate unreliable or fraudulent contractors:
Immediate disqualifiers (walk away):
- No RBQ license or expired license: Illegal to operate without valid license. You’ll have no recourse through RBQ complaint process if problems arise.
- Pressure to skip permits: “We can save you time and money by not getting permits.” This makes YOU criminally liable for unpermitted work.
- Cash-only payments: “Pay cash and save the taxes.” This is tax fraud, provides no paper trail for recourse, and suggests contractor operates outside legal system.
- Large upfront deposits (over 15%): Quebec standard is 10-15% deposit maximum. Larger requests indicate financial instability or fraud risk.
- No written contract: “We’ll work on a handshake.” Verbal contracts are unenforceable for projects over $3,000 in Quebec.
- Reluctance to provide insurance certificates: Every legitimate contractor readily provides current insurance documentation.
- No physical business address: Only has cell phone number and email. Legitimate businesses have verifiable locations.
Serious warning signs (investigate further):
- Quote significantly lower than others (30%+ below): Either contractor doesn’t understand scope, plans to cut corners, or will hit you with change orders.
- Vague or incomplete quote: Lacks detailed breakdown of work, materials, timeline, payment schedule, or exclusions.
- Can’t provide recent local references: Only offers references from years ago or outside the region.
- Negative online reviews mentioning: Abandoning projects mid-work, demanding extra payments beyond contract, poor quality, unresponsiveness, or RBQ complaints.
- High-pressure sales tactics: “This price is only good if you sign today.” Legitimate contractors understand you need time to decide.
- Unwilling to answer detailed questions: Evasive about experience, equipment, employees, or project approach.
Getting and comparing quotes (best practices):
How many quotes to obtain:
Recommendation: 3-5 detailed quotes from qualified contractors.
- Fewer than 3: Insufficient for price comparison
- More than 5: Diminishing returns; becomes difficult to evaluate thoroughly
What to request from each contractor:
1. Site visit and assessment: Legitimate contractors ALWAYS visit site before quoting. Refuse quotes from contractors who haven’t seen your property.
2. Detailed written proposal including:
- Complete scope of work description
- Itemized cost breakdown (excavation, disposal, foundation work, backfill, etc.)
- Materials specifications (concrete strength, rebar sizing, waterproofing products)
- Timeline with key milestones
- Payment schedule tied to completion milestones
- What’s explicitly excluded from quote
- Warranty terms for workmanship and materials
- How change orders will be handled and priced
3. Supporting documentation:
- Copy of current RBQ license
- Certificate of Insurance
- CNESST confirmation if applicable
- References list with contact information
Comparing quotes effectively:
Step 1: Verify identical scope
Ensure all contractors quoted the same work. Pay attention to:
- Excavation depth and dimensions
- Foundation specifications (footing size, wall thickness)
- Concrete strength grades
- Waterproofing type and coverage
- Drainage system specifications
- Backfill and grading approach
Step 2: Compare line items individually
Don’t just compare total prices. Review each cost component:
- Excavation rate per m³
- Disposal costs
- Foundation materials and labor
- Timeline differences
Step 3: Evaluate quality indicators
Lower price doesn’t always mean better value. Consider:
- Materials quality (30 MPa vs 35 MPa concrete makes difference)
- Waterproofing thoroughness (membrane only vs membrane + drainage board + weeping tile)
- Warranty terms (1 year vs 5 year workmanship warranty)
- Contractor experience and reputation
Step 4: Clarify exclusions
Identify what each quote excludes:
- Permits and engineering fees
- Utility relocations
- Unexpected rock removal
- Site restoration beyond basic grading
Get supplementary quotes for excluded items to calculate true total cost for each contractor.
Contract essentials (protect yourself legally):
Never begin work without a comprehensive written contract. Quebec law requires written contracts for renovation work over $3,000, but even for smaller projects, written agreements protect both parties.
Essential contract clauses:
1. Parties and property:
- Your name and contact information as property owner
- Contractor’s business name, RBQ license number, address
- Property address where work will be performed
2. Scope of work:
- Detailed description of all work included
- Reference to approved plans and specifications
- Materials specifications
- Clear list of exclusions
3. Price and payment terms:
- Total contract price
- Payment schedule tied to completion milestones
- Maximum 10-15% deposit
- 10% holdback until final completion and deficiency correction
- How additional work (change orders) will be priced and approved
4. Timeline:
- Projected start date
- Substantial completion date
- Key milestone dates
- Provisions for weather delays or unforeseen conditions
5. Permits and Code compliance:
- Who obtains permits (typically contractor)
- Confirmation that all work will comply with Quebec Construction Code
- Responsibility for failed inspections
6. Insurance and liability:
- Contractor maintains adequate insurance throughout project
- Property owner added as additional insured
- Liability for property damage or injuries
7. Warranty:
- Workmanship warranty duration (minimum 1 year recommended)
- What’s covered under warranty
- Process for warranty claims
8. Dispute resolution:
- Process for resolving disagreements
- Mediation or arbitration provisions
- Legal jurisdiction (typically Quebec Superior Court)
9. Termination clause:
- Conditions under which either party can terminate
- Notice requirements
- How partially completed work and payments are handled
Can my existing foundation support a house extension?
Short answer: Only a structural engineer can determine this definitively.
This is the question that causes the most project cancellations and budget shocks. Homeowners budget for excavation and extension construction, then discover their existing foundation requires $50,000-$100,000 in reinforcement or underpinning work. Montreal’s unique challenges—older houses with shallow foundations, problematic clay soil, and strict modern Code requirements—make foundation evaluation absolutely critical before committing to any house extension excavation project.
Why Montreal houses frequently need foundation work for extensions:
1. Age and construction standards:
Most Montreal houses were built before 1980 using standards that seem inadequate today:
- Shallow foundations: Many older houses have footings only 3-4 feet deep—inadequate by modern standards requiring minimum 5 feet (1.5m) below grade for frost protection
- Unreinforced concrete: Older foundations often lack steel reinforcement (rebar), making them weaker and more prone to cracking
- Thinner walls: 6-8 inch thick foundation walls were common; modern Code requires 8-10 inches minimum depending on depth and soil conditions
- No waterproofing: Older houses typically have no foundation waterproofing, just parged exterior finish
2. Montreal’s problematic clay soil:
Montreal sits on extensive clay deposits. Clay soil causes foundation problems:
- Expansive properties: Clay swells when wet, shrinks when dry. This constant movement stresses foundations
- Poor drainage: Clay is nearly impermeable, causing water to pool around foundations rather than draining away
- Frost heave: Clay holds moisture that freezes in winter, pushing foundations upward (heaving)
- Settlement: Clay compresses under load, causing uneven settling over decades
3. Modern Code requirements vs. historical standards:
Quebec Construction Code 2020 imposes requirements that existing foundations often don’t meet:
- Minimum frost depth: 1.5m (5 feet) below finished grade in Montreal region
- Footing width: Must be calculated based on soil bearing capacity and loads (typically 24-36 inches wide for two-storey structures)
- Reinforcement: Mandatory rebar in footings and foundation walls
- Waterproofing: Comprehensive dampproofing or waterproofing systems required
- Drainage: Perimeter drainage (weeping tile) mandatory
When you add an extension, the entire system—old and new portions—must meet current Code. This often means retrofitting existing foundations to modern standards.
4. Signs your foundation may not support an extension:
Before even consulting an engineer, look for these warning signs:
1. Visible foundation damage: Vertical cracks wider than 1/4 inch, horizontal cracks (very serious), stair-step cracks in block foundations, bowing or bulging walls.
2. Water infiltration: Wet basement walls, efflorescence (white mineral deposits), mold or mildew, musty odors.
3. Evidence of movement: Sloping floors (check with level), doors and windows that stick or won’t close properly, gaps between walls and ceiling or floor, cracks in interior drywall above doors and windows.
4. Foundation settling: Older houses often show signs of settling—uneven floors, cracks in interior walls, sticking doors and windows.
When you’ll definitely need foundation work for your house extension:
Adding a second storey: Your existing foundation must support significantly more weight. Most single-storey foundations weren’t designed for multi-storey loads. Expect foundation reinforcement or replacement.
Lateral extensions (adding to the sides or back): New extension foundations must match or exceed the depth of existing foundations. If extending an old house with shallow foundations, you’ll need deeper foundations for the new section.
Basement extensions (digging down): This requires underpinning—excavating beneath existing foundations while keeping your house stable. This is complex, expensive work requiring specialized contractors.
Crawl space conversion to full basement: Similar to basement extensions, you’ll need underpinning to lower the floor and often foundation replacement to create adequate ceiling height.
What a structural engineer evaluation includes for house extension excavation:
Visual inspection:
- Foundation wall condition
- Existing crack patterns
- Signs of movement or settling
- Water damage or efflorescence
- Current foundation type and depth
Measurements:
- Foundation footing width and depth
- Wall thickness
- Current load-bearing capacity
Soil analysis:
Often requires geotechnical testing from a specialized soil laboratory to determine:
- Soil bearing capacity
- Clay composition and stability
- Water table levels
- Recommendations for foundation design
Load calculations:
Engineer determines if existing foundation can handle:
- New extension weight
- Snow loads
- Live loads (occupancy)
- Safety factors required by Code
Your foundation options for house extension excavation:
| Option | Description | Cost Impact | Timeline |
|---|---|---|---|
| 1. Existing foundation is adequate | Rare, but possible if foundation is new and you’re adding lightweight single-storey | Minimal | – |
| 2. Foundation reinforcement | Strengthen with additional concrete, steel supports, extended footings | $15,000-$35,000 | 2-3 weeks |
| 3. Underpinning | Excavate beneath existing foundation, pour new deeper footings, reinforce | $60,000-$100,000+ | 4-5 weeks |
| 4. Complete replacement | Demolish and replace failing foundation sections with new reinforced concrete | $40,000-$80,000+ | 3-4 weeks |
Critical warning signs your foundation needs work before house extension excavation:
- Vertical cracks wider than 1/4 inch: Indicates significant structural movement
- Horizontal cracks: More serious than vertical; suggests foundation wall failure
- Bowing or bulging walls: Emergency situation—foundation is failing
- Water infiltration: Compromises foundation integrity over time
- Uneven floors: Foundation settling or failure
- Doors and windows sticking: House shifting due to foundation issues
The Montreal clay soil factor in house extension excavation:
Quebec’s Régie du bâtiment specifically cautions homeowners about clay soil risks. Before any house extension excavation:
- Hire a geotechnical specialist or soil laboratory
- Get soil bearing capacity analysis
- Understand pressure resistance of your specific soil
- Plan for proper shoring during excavation to prevent cave-ins
Warning: Skipping these steps on clay soil can literally cause your house to collapse during excavation. Not worth the risk.
Your action plan for house extension excavation:
Step 1: Hire a structural engineer experienced with Montreal house extensions ($3,000-$8,000 investment).
Step 2: Get soil analysis if recommended (typically $1,500-$3,000).
Step 3: Review engineer’s recommendations and get detailed cost estimates for required foundation work.
Step 4: Factor foundation work costs into your total budget BEFORE committing to the extension.
Reality check: Many homeowners discover foundation work costs $50,000-$100,000 on top of their expected house extension excavation costs. This surprise can make or break project feasibility. Know your foundation situation early in the planning process.
Bottom line: Don’t guess about your foundation’s capacity. The cost of a structural engineering evaluation is tiny compared to catastrophic failure during or after construction. Your family’s safety and your financial investment depend on getting this right.
Information current as of October 2025. Municipal regulations may change. Always verify requirements with your specific municipality before beginning work.