In general prefer a permeable surface to impervious asphalt or concrete. With impervious surfaces water will runoff into the storm drain carrying pollutants. With a permeable surface the water is redirected into the ground where it can be filtered by microorganisms and recharges aquifers. What's important is a porous base which provides stability for cars (6-inch subbase of 1 and 1/2 inch rock topped with 4-inch base of 3/4 rock). On top of that gravel or ceramic pavers can be added. Gravel can mean more maintenance when there's snow to remove. Ideal solution will depend on soil conditions + municipal by-laws.
Cost: $2,000 on avg, $5-$20/sqft
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