More Thoughts on Gravel Surfaces

The Scarsdale Board of Trustees is now considering changing village code to count gravel surfaces in the calculation of lot coverage. Currently gravel driveways are considered "pervious" ... and with this change, gravel would be treated as "impervious," similarly to asphalt. We spoke to Scarsdale architect Bart Hamlin about the proposed change and here is what he shared.

Do you think this moratorium has had an effect on building projects? Renovations? Demolitions?

In answer to your immediate question - Yes, I am sure this change of requiring gravel to be counted as lot coverage will have an impact on some projects. If there is a great deal of lot coverage from walks, patios and driveway - this may actually limit your building coverage to less than allowable building coverage. In this case, not counting some of the driveway coverage because it is converted to gravel will allow you to increase your building coverage. This fact may be enough to make a renovation/addition project worthwhile. To cite a typically situation, older houses do no have family rooms. These houses often do have driveways that go to the back of the property (resulting in more lot coverage). Converting some of that driveway to gravel (and therefore not count towards lot coverage) had allowed the building footprint to be increased thus allowing the addition of a family room to an older home.

The lot coverage regulations put limits on two different conditions:
1) total allowable lot coverage for principal building (your house) and
2) total allowable for all lot coverage including house and all other impervious coverage.

Although there is a lot of talk about how the building will get bigger if the gravel is not counted - what people have failed to describe is that there is an primary component of the regulation that limits the building coverage. So the building cannot be as big as the total allowable total lot coverage. The building footprint can only be as big as the maximum allowable building coverage.

I do not know if there is a direct correlation between lot coverage and demolition. I think the primary reason for full house demolition and removals is that renovating and updating old houses is difficult, costly and, most importantly, hard to estimate the full cost until after you do internal demolition to see the state of the structure and mechanicals. On the other hand, new buildings - including the cost of full house demolition and removal, is much more predictable which is important for a developer and home owners who wants to reduce their risk of cost overages.

If the driveway is considered impervious, approximately how many square feet does that take away from the proposed home? How much smaller does it have to be?

Back to the relationship of building coverage and total coverage. If walkway, patio and driveway coverage is very large, than the building coverage may be less than the maximum allowable. Conversely, reducing total lot coverage by making the house closer to the street and/or making the garages face the street could help reduce lot coverage of walkways and driveways. This will keep "other" coverage lower make it more likely you can obtain the max allowable building coverage, and - it will also have an effect on the entire street landscape. In other words, be careful of unintended consequences. (Note - credit to Dan Hochvert for bringing up unintended consequences in a recent discussion.)

Another factor in this related discussion of building size is the allowable floor area of the house - meaning not just the footprint but all the applicable areas of every story of the house - sometimes including basements and third floors - depending on the design. The total allowable floor area is calculated based on the lot size and a floor area ratio that varies according to what zoning district the house is located in.

One other thought - it is not the gravel that is impervious. Water will pass through the space between gravel stones. It is the substrate that can become impervious. It really depends on how the driveway is constructed. A more scientific process would include an understanding of different construction types and testing of the actual substrate before gravel is applied in order to know if the surface is impervious, partially impervious or pervious.

All said, there are many factors - and counting gravel as pervious or impervious is only one factor.

Deborah Goldreyer and Bart Hamlin of Hamlin Goldreyer Architects have received, for the third year in a row, the prestigious "Best of Westchester" award from the readership of Westchester Magazine. Hamlin Goldreyer are a husband and wife team that work in their Scarsdale residence in the Greenacres neighborhood. They have been providing high-end, custom residential design services for 24 years in Westchester County, Fairfield County and Long Island - with most of their projects being built in Scarsdale. This local design team was selected as one of the 12 best architectural firms in Westchester County by a panel of judges in 2012, also for Westchester Magazine. In addition to building designs, Hamlin Goldreyer provide a full range of interior design services including kitchens, bathrooms, family rooms and libraries. You can view their work at their website - ScarsdaleArchitects.com - and on Houzz.com.