Permeable Surface Calculator
Calculate the impact of replacing asphalt with permeable surfaces.
Water Saved
29.7m³
per year
Reduction
84%
less runoff
Area
37 m²
400 pi²
Est. Cost
$7,200
to $11,200
Runoff Comparison
Permeable Surface Options
| Surface | Permeability | Cost/sq ft |
|---|---|---|
| Permeable Pavers | 85% | $18-$28 |
| Gravel / Crushed Stone | 95% | $3-$8 |
| Grass Pavers (grid) | 90% | $12-$20 |
| Porous Concrete | 80% | $15-$25 |
| Natural Lawn | 70% | $2-$5 |
Note
Costs are estimates for the Montreal area. Actual prices may vary based on site conditions.
Ready to replace your asphalt?
We install permeable surfaces: pavers, gravel, and more. Free estimate.
514-900-3867How to use this tool
Enter the area of impervious surface you want to replace, such as an asphalt driveway or concrete patio. Select the replacement material: permeable pavers, gravel, porous concrete, or grass pavers. The calculator estimates the runoff reduction percentage, annual stormwater diverted from sewers, and the approximate cost difference compared to traditional impervious installation.
Why it matters
Replacing impervious surfaces with permeable materials is one of the most impactful residential actions for stormwater management. In Montreal, aging combined sewers can overflow during heavy rain, sending untreated water into the St. Lawrence River. Every square metre of permeable surface helps: it allows rainwater to infiltrate the ground rather than running into storm drains, recharges groundwater, reduces basement flooding risk, and can lower the urban heat island effect by retaining moisture.