The London Basement Project Estimator
Turn one giant plumbing quote into a realistic after-grant, after-tax number. Select the items in your package, enter the pre-tax quote, and see how much the City pays versus what actually leaves your bank account.
Estimate Your Possible Out-of-Pocket Cost
Enter the eligible pre-tax amount shown for each separate quote line. The tool adds 13% HST and applies 90% and the cap to every item independently—the same distinction a bundled total misses.
Item-by-item estimate
This is a planning estimate, not City approval. Save your result and get the application checklist.
Method: for each entered item, estimated grant = the lower of 90% of the tax-inclusive eligible amount or that item's City maximum. Cosmetic restoration, unrelated waterproofing, and other ineligible work should not be entered. Sources checked July 22, 2026.
Bundle Quotes Are Hard to Read
A single $8,000 to $12,000 quote can hide three separate grant caps. This estimator rebuilds the cap total from the work you select.
HST Changes the Real Number
The homeowner sees the tax-inclusive invoice. That is why the estimator adds 13% HST before applying the 90% grant rule and hard caps.
The Red Zone Matters
Once the City grant hits the selected cap, the green bar stops growing and extra invoice increases land on the homeowner side.
Need the quote formatted correctly?
The calculator only helps if your contractor's quote is itemized the way the City expects. Get the checklist before you submit anything.
Download the Free Grant ChecklistHow the Basement Flooding Grant Math Actually Works
The City of London's Basement Flooding Grant Program can reimburse 90% of eligible construction cost up to a separate maximum for each approved work type. That means a single total from a contractor is not enough to estimate the result accurately.
The planning calculator above applies the public formula and caps item by item. The City still determines eligibility, eligible cost, approval, and final payment.
1. The 90% Rule vs. The Hard Caps
The current program provides 90% of City-accepted eligible construction costs up to strict maximum limits for each work type. If 90% of an eligible line is higher than its cap, the planning estimate stops at the cap.
- Backwater valve: $1,800.
- Sewage ejector and holding tank: $6,000.
- Sump pit and pump with existing weeping tile disconnection: $4,000.
- Additional weeping tile disconnection: $2,400.
- Storm private drain connection: $7,000.
- Storm building sewer: $3,000.
- Battery backup installed with a new sump pump: $1,400.
- Reverse-grade driveway sump pit and pump: $4,000.
2. Factoring in the Ontario HST
One of the most common questions homeowners ask is: "Does the grant cover the taxes?" Yes. The City of London calculates your 90% reimbursement based on the final, tax-inclusive total of your invoice. Our calculator automatically applies the 13% Ontario HST to your base quote to ensure your out-of-pocket estimate is accurate down to the penny.
3. Multi-Item Bundle Quotes
If your home requires both a backwater valve and a new sump pump, each part should be identifiable on the quote. Enter each eligible line separately so a capped item cannot borrow unused room from another cap.
4. How Many Quotes the Application Needs
The program by-law sets the estimate count by the quoted project amount: one estimate below $5,000, two estimates from $5,000 through $10,000, and three estimates above $10,000. The live quote reminder above follows those thresholds; confirm the current application instructions before submission.
đź“Ť Avoid a preventable problem: Submit the required itemized estimates and wait for written approval before work begins. Review the grant application rules guide before signing a contract.
Primary sources
City of London Basement Flooding Grant Program and By-law A.-7562-160. Sources checked July 22, 2026.