Signing an interlock paving contract without understanding the fine print can lead to costly disputes, substandard workmanship, and long-term pavement failure. Whether you’re installing a new driveway, patio, or walkway in Ottawa, your contract is your only legal protection against shortcuts and inferior materials.
This comprehensive interlock contract checklist will help Ottawa homeowners identify essential clauses, spot red flags, and ensure their investment is protected from base depth issues to warranty coverage.
Why Your Interlock Contract Matters
In Ottawa’s freeze-thaw climate, proper interlock installation is critical. Without a detailed contract specifying base depth, drainage, and compaction standards, contractors can cut corners that lead to:
- Sinking and settling pavers within the first year
- Water pooling and ice buildup in winter
- Cracked or shifted stones from frost heave
- Voided warranties due to vague language
- Disputes over project scope and materials
A well-written contract protects both parties and ensures your interlock project meets Ottawa’s climate demands and industry standards.
Essential Contract Elements: Your Complete Checklist
1. Project Scope with Specific Dimensions
Your contract must include exact measurements, not estimates. Require total square footage, length and width dimensions, any curved sections with detailed drawings, and location of borders or accent bands.
Example clause: “Project includes 450 square feet of interlocking pavers in a herringbone pattern, measuring 20 feet wide by 22.5 feet long, with a charcoal border course as shown in attached diagram.”
2. Base Depth Specification
This is the most critical clause. Ottawa contractors should specify minimum base depths:
- Driveways: 10-12 inches of compacted granular base
- Patios and walkways: 6-8 inches of compacted base
- Pool decks: 6-8 inches minimum
Sample base depth clause: “Base preparation will include excavation to a minimum depth of 10 inches below finished grade. Base will consist of 8 inches of 3/4-inch clear crushed limestone (OPSS Granular A) and 2 inches of concrete sand bedding layer. All base layers will be compacted in 2-inch lifts to 95% Proctor density.”
Never accept vague language like “appropriate base” or “standard depth.” These terms are unenforceable and allow contractors to use insufficient materials.
3. Base Material Specification
Not all stone is created equal. Your contract should specify 3/4-inch clear crushed limestone (OPSS Granular A or equivalent), crushed angular stone (not rounded river rock), and concrete sand for bedding layer (not masonry sand).
Red flag: Contracts that don’t specify base material or use terms like “gravel” are insufficient. Gravel doesn’t compact properly and leads to settlement.
4. Compaction Standard: 95% Proctor Density
Base material must be compacted to prevent settling. Require compaction in 2-inch lifts, 95% Proctor density standard, and use of a plate compactor or roller compactor.
Example clause: “All granular base layers will be compacted using a vibratory plate compactor in maximum 2-inch lifts to achieve 95% Standard Proctor Density (ASTM D698).”
5. Drainage Plan with Specific Slope
Proper drainage is essential in Ottawa’s climate. Your contract must include minimum 2% grade (1/4 inch per foot) away from structures, drainage direction specification, catch basin or drain locations if required, and weeping tile for problem areas.
Sample drainage clause: “Finished surface will slope at a minimum grade of 2% (1/4 inch per foot) away from the house foundation, directing water toward the front yard lawn area. A 4-inch perforated weeping tile will be installed along the foundation side, connected to the existing storm drain.”
Poor drainage causes ice buildup, water pooling, and erosion under the pavers. Don’t accept a contract without a drainage plan.
6. Geotextile Fabric Placement
Geotextile fabric prevents soil migration into the base layer. Your contract should specify placement between subgrade soil and granular base, overlap of fabric seams by at least 12 inches, and fabric weight (non-woven landscape fabric, minimum 4 oz per square yard).
7. Edge Restraint Specifications
Edge restraints prevent pavers from spreading and shifting. Require plastic spike edging, aluminum edge restraint, or concrete curb on all perimeter edges, secured to base with spikes every 12 inches.
8. Polymeric Sand Type and Application
Polymeric sand locks pavers together and prevents weed growth. Specify polymeric sand (not regular mason sand), swept into joints and activated with water mist, and color matched to complement paver color.
9. Sealing Timing and Product
Some contractors include sealing, others don’t. If included, specify timing (wait 90 days after installation for polymeric sand to cure), sealer type (water-based or solvent-based), and number of coats (typically 1-2 coats).
10. Warranty Clause (Materials + Workmanship)
A comprehensive warranty is your long-term protection. Look for minimum 2-5 years workmanship warranty covering settling, shifting, and drainage issues, pass-through of manufacturer warranty (typically 25-year limited), specific coverage for repairs to base and re-leveling, and clear exclusions (snow plow damage, vehicle abuse, homeowner modifications).
Sample warranty clause: “Contractor warrants workmanship for a period of 5 years from completion date. Warranty covers settling exceeding 1/4 inch, base failure, drainage problems caused by improper installation, and paver shifting. Warranty does not cover damage from snow removal equipment, vehicle impacts, or homeowner excavation.”
11. Payment Schedule
A fair payment schedule protects both parties. Standard structure: 10-30% deposit upon contract signing, 40-50% mid-project upon base completion and paver delivery, and 20-40% final payment upon completion and homeowner approval.
Red flag: Contractors demanding 50% or more upfront, or full payment before completion, pose a risk. Never pay in full until you’ve inspected the finished work.
12. Timeline with Weather Delays Clause
Ottawa’s weather is unpredictable. Your contract should include specific or “on or about” start date, completion timeframe in working days (e.g., 5-7 days), and weather delay extensions for rain, extreme heat, or cold.
13. Change Order Process
Projects sometimes require modifications. Establish a clear process requiring written approval for all changes, updated pricing before work begins, and documentation of timeline impacts.
14. Cleanup Responsibility
Don’t assume cleanup is included. Specify removal of all excess materials and debris, sweeping of pavers and adjacent surfaces, disposal of excavated soil, and restoration of any disturbed landscaping.
Red Flag Clauses to Watch For
Some contract language is designed to protect contractors at your expense. Be wary of these problematic clauses:
Overly Restrictive Warranty Voids
Red flag language: “Warranty is void if homeowner uses any snow removal service, applies de-icing salt, or parks vehicles on surface.”
Why it’s problematic: These conditions make the warranty essentially useless for a driveway. You need to use your driveway normally.
Better language: “Warranty excludes damage from snow plow blade impacts or excessive salt application (more than manufacturer recommendations).”
No Settling Responsibility
Red flag language: “Some settling is normal and expected. Contractor is not responsible for any settling or sinking.”
Why it’s problematic: This clause allows contractors to walk away from improper base preparation.
Better language: “Minor settling up to 1/4 inch is normal. Settling exceeding 1/4 inch within the warranty period will be corrected by contractor at no charge.”
Vague Material Descriptions
Red flag language: “Standard paving stones” or “appropriate base materials.”
Why it’s problematic: Leaves room for inferior products or cheaper alternatives.
Better language: Specify exact paver brand, color, thickness, and base material specifications.
Front-Loaded Payment Schedule
Red flag language: “50% deposit required to schedule project, 50% due upon material delivery.”
Why it’s problematic: You have no leverage if quality or timeline issues arise after payment.
Better structure: Maximum 30% deposit, 40% mid-project, 30% upon completion.
Warranty Exclusions to Negotiate
While some warranty exclusions are reasonable (direct impact damage, natural color fading, homeowner excavation, acts of nature), others can be negotiated including allowance for moderate salt use per manufacturer specs, vehicle traffic exclusions limited to heavy commercial vehicles only, coverage for excessive settling beyond normal 1/4 inch, and drainage issues caused by improper grade.
Questions to Ask Before Signing
Before committing to a contract, ask your contractor:
- “Can you add the specific base depth to the contract?” – If they refuse, consider it a red flag.
- “How will you handle drainage on my property?” – They should have a site-specific answer.
- “What compaction equipment do you use?” – Look for plate compactor or roller.
- “Is your warranty transferable if I sell my home?” – Adds value to your property.
- “Do you carry liability insurance and WSIB coverage?” – Ask for proof of both.
- “What happens if it rains during installation?” – Understand their weather protocol.
- “Can I see references from projects completed 3-5 years ago?” – Long-term performance matters.
Contract Review Checklist
Use this checklist before signing any interlock contract in Ottawa:
- Exact square footage and dimensions specified
- Base depth specified (10 inches for drives, 6-8 inches for patios)
- Base material type (OPSS Granular A or equivalent)
- Compaction standard (95% Proctor density)
- Drainage plan with slope percentage
- Geotextile fabric included
- Edge restraint type specified
- Polymeric sand specified
- Paver brand, color, and thickness
- Workmanship warranty (minimum 2 years)
- Fair payment schedule (max 30% deposit)
- Realistic timeline with weather clause
- Change order process defined
- Cleanup responsibilities listed
- Contractor license and insurance proof
If you can’t verify 12 or more of these elements, request contract revisions before signing.
Why Base Depth and Drainage Matter Most in Ottawa
Ottawa experiences 100+ freeze-thaw cycles per winter. When water infiltrates an inadequate base, it freezes and expands, creates frost heave lifting pavers, then thaws creating voids in the base material. Pavers settle into these voids creating uneven surfaces. This cycle repeats 100+ times per winter, accelerating damage.
A proper 10-inch compacted base with 2% drainage slope prevents water accumulation, eliminating the freeze-thaw cycle’s destructive effects. This is why your contract must specify both elements – they work together to ensure long-term performance.
Working with Interlock Experts
At Interlock Experts, transparency is our foundation. Every contract we provide includes:
- Detailed base depth specifications (minimum 10 inches for driveways)
- OPSS Granular A crushed limestone base material
- 95% Proctor compaction standard with vibratory equipment
- Site-specific drainage plan with slope calculations
- 5-year workmanship warranty covering settling, drainage, and base failure
- Fair payment schedule (25% deposit, 40% mid-project, 35% completion)
- Realistic timelines with weather contingency clauses
- Material specifications including paver brand, color, and thickness
We believe you should never have to guess what you’re paying for. Our contracts are written in plain language, and we walk every client through each clause before signing.
Need help reviewing an interlock contract, or want to see how our proposals compare? We offer free contract reviews for Ottawa homeowners, even if you’re working with another contractor.
For detailed project pricing and contract examples, visit our pricing page. To discuss your specific project and get a transparent proposal, visit our contact page or call us directly at +1 613 981 0199.
Learn more about our comprehensive interlock installation services, including driveways, patios, walkways, and repairs, on our services page.
Protect Your Investment with a Strong Contract
Your interlock contract is more than paperwork – it’s your protection against substandard work, costly repairs, and legal disputes. By ensuring your contract includes specific base depth clauses, detailed drainage plans, and comprehensive warranties, you’re investing in long-term performance and peace of mind.
Don’t sign a contract you don’t fully understand. Ottawa’s climate demands precision, and your contract should reflect the same attention to detail that goes into a properly installed interlock surface.
Ready to get started with a contractor who puts everything in writing? Contact Interlock Experts today at +1 613 981 0199 for a detailed proposal with no hidden terms, no vague language, and complete transparency from start to finish.