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A challenge to Evanston’s restrictions on decks may lead to a change in city rules that now restrict their size.

Those rules assume that decks — even ones with spacing between the deck boards — are impervious — that they add runoff into the sewer system by not letting any water that falls on them soak into the ground.

But attorney Anthony Hind, representing the owners of a home at 2327 Park Place in northwest Evanston, challenged that theory during a Zoning Board of Appeals hearing this week.

Hind, of Central Law Group in Evanston, says it’s a common-sense thing — that when dealing with decks with gaps between the slats and a pervious surface below the deck, water moves between the slats, falls to the ground within inches of where the randrops would have hit anyway, and then soak into the ground.

After hearing arguments from Hind and city staff, the ZBA voted to continue the issue until the next board meeting on Tuesday, July 21.

The city’s zoning code sets limits for the amount of impervious surface on a property — which in addition to decks is considered to include the square footage of any building as well as paved walkways and driveways and similar surfaces. The limit is 45 percent impervious surface in the R1 zone, and higher in other zones.

Other communities are split in whether they treat decks as impervious or permeable surfaces — with many, including Charlotte, N.C. and the surrounding Mecklinburg County as well as the state of Maryland saying they are permeable, while communities in other areas, like North Central Wisconsin, are split on the issue.

At least one group of academic researchers has concluded that wood decks are permeable, and they include Bruce Ferguson of the University of Georgia, who literally wrote the book on porous paving materials.

Damir Latinovic, the city’s planning and zoning administrator, says the type of surface under a deck can have a big impact on its permeability. Many decks have gravel underneath, he says, and the city code calls gravel areas impervious.

But there’s no question that different cities classify decks differently, Latinovic says, and the zoning code may need some clarification or modification.

With the code now giving a break from impervious surface rules for permeable pavers and similar products, maybe it should do so for decks as well, Latinovic added.

He said more action on the issue could happen within the next month or two.

In the meantime, Hind says he’s hoping that, with some modifications to his clients’ plans, their deck project will win approval at the next ZBA meeting without having to actually address the broader issue.

Bill Smith is the editor and publisher of Evanston Now.

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2 Comments

  1. Gravel impervious?

    Note to City Planning and zoning people… gravel is used in drainage projects all over the world – why is it different here?  Please change this silly rule. 

    Respectfully, Brian G. Becharas (who has pea gravel under his deck for better drainage!)

    1. Gravel under decks

      I agree. We have gravel under our back porch where there was formerly an open deck. I see no reasonable objection to this because it's not an impermeable surface.

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