These are real, recurring mistakes BaseWorks sees when brought in to fix or complete another contractor's problem basement lowering project. Every one of them is avoidable.
1. Choosing the Cheapest Quote Without Checking Scope
A quote 30-40% below others is almost always missing scope — permit fees, the new slab, or a lesser concrete spec.
Fix: compare quotes line-by-line, not just the total.
2. Skipping the Permit to Save Time
Leads to stop-work orders, forced re-exposure of completed work, and resale complications.
Fix: never start excavation before permit approval, full stop.
3. Choosing Bench Footings for a Legal Suite Without Checking Room Sizes
Loses 12-24 inches of floor width per wall, which can make rooms fail OBC minimum size requirements.
Fix: have the engineer confirm room-by-room compliance before choosing the method. See our bench footings vs. underpinning guide.
4. Not Verifying WSIB and Liability Insurance
Homeowner becomes liable for injuries or property damage if the contractor is uninsured.
Fix: request current WSIB clearance and $5M liability proof before signing.
5. Underestimating the Waterproofing Scope
Lowering exposes new foundation wall area that needs waterproofing — skipping this leads to leaks within 1-2 years.
Fix: bundle waterproofing into the same project rather than doing it later.
6. Ignoring Party Wall Requirements on Semi-Detached Homes
Skipping neighbour notification can halt the project mid-construction and create legal disputes.
Fix: confirm the contractor's engineer includes party wall notification in the permit package.
7. Not Budgeting a Contingency
Unexpected soil conditions or utility relocations are common — homeowners with zero buffer face difficult mid-project decisions.
Fix: budget 10-15% contingency above the fixed-price quote.
8. Finishing the Basement Before Confirming Final Inspection Sign-Off
Drywalling over unapproved work creates major problems if an inspector later requires access.
Fix: wait for final structural sign-off before finishing work begins.
Frequently Asked Questions
Skipping the permit is the most expensive mistake, since fixing it after the fact can mean re-exposing completed structural work for retroactive engineering review, plus potential stop-work orders and resale complications. What would have cost a few thousand dollars in permit fees can turn into tens of thousands in remediation.
Yes, in most cases, but remediation is significantly more expensive than doing it correctly the first time. Common fixes include re-engineering and redoing bench footings that don't meet room size requirements, or bringing unpermitted work up to code retroactively with an engineer's full re-assessment.
Request current WSIB clearance and $5M liability insurance proof, confirm they manage the full permit process themselves, ask for 2-3 references from similar Toronto projects, and get everything in a written fixed-price contract before work begins. See our full guide on questions to ask an underpinning contractor for the complete vetting checklist.
Ask directly: "What happens if the permit gets rejected?", "Can you show me your bay sequencing plan?", and "What's your concrete specification in MPa?" A contractor who can't answer these clearly, or who deflects, is a red flag worth taking seriously before signing anything.