Agenda - Planning Commission - 08/08/2005

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?loarArea t?otia (?,4t?), The model here is similar but requires more care because floor area is a more precise measure and directly involves the potential of multiple floors. The need to consider height is even more critical because FAR does not distinguish between ground- and upper-floor expansion. Using FAR may be a better tool for regulating teardowns in neighborhoods with a mix of housing st/les, where the homes were built by differ- eot developers but are similar in size. I-[eight. Hei§ht ts aD important element in neighborhoods where the number of sro- des and roof pitches are defining features. Dramatic changes in hei§ht can be a problem. It is likely that in neighborhoods with ranch, Cape Cod, or split:level housing st/les the maximum hei§ht established by zoning dis- trict regulations is substantially higher than the height of the existing building stock, The standards should be amended to respect existing character. Even in nei§hborhoods with two-story houses, the original homes may have [ow roof pitches-5/t2, for exam- pie. With end §abies, adding z5 feet to the rear of a 2z~-foo{-wide house would raise the roof from five feet to a little more than el§bt feet. If the remodeling involved a change in roof pitch to 9/t2, the roof hei§ht would needy triple, from five feet to more than t4.6 feet. While the three-foot change would be merely noticeable, a 9.6-foot change is simi- lar to adding a story. Building Volume Ratio (BVR), 8~R is the most flexible of the re§uladons because chon§es are tracked automatically, forcing the architect to make trade-offs. In §eneral, BVR is not recommended as a primary regulatory tool for teardowns in existing neighborhoods because it requires detailed explanation and a change in the re§ulation format most familiar to residents. The one exception is the community where historic development patterns create sig- nificant size gradients, For example, in many New England seaport towns, captain's houses transition quick(y to small, historic Cape Cods- ail within a few blocks. While it is possible to divide the nei§hborhood into smaller sections with overlays desi§nating areas of varying 8VRs, this may result in mapping battles with homeowners wanting to move the overlay boundaries for personal gain. Thus, building volume can be tied to a radius around the lot so overlay district lines need not be drawn. ADDITIONAL/~EASURE5 In older neighborhoods with mature trees, house size is by no means the only determi- nant of community character. The saplin§s planted during the development of older sub- divisions may now be as tall as 6o feet, adding to both the economic and aestheti'c value of the neighborhood. Vegetation is equally important in determining character. A strict requirement to preserve front-yard vege- ration will help preserve that. character. Communities with at-risk neighborhoods have two additional volume measures where the increase in floor area or BVR is offset by an increase in landscape volume ratio. Landscape Valume Ratio (LVR). LVR measures soft vegetative volume. In mature residential communities this is as important as building volume because streets are likely to be lined with mature trees and the lots cov- ered with mature landscaping. In many older neighborhoods landscape volume may be larger than building volume, A'teardown is likely to result in a loss of mature vegetation. The LVR provides a means of measuring this etement of neighborhood character. Site Volume Ratio ($VR). SVR combines the two volume measures (BVR and LVR) and is calculated by subtracting the BVR from the LVR. Thus, a positive SVR indicates a land- scape volume greater than the building vol- ume. A negative value indicates building vol- ume as the dominant value. The SVR ts a means of calculating the existing community character by taking into account both the buiidin§ and the landscapin§. The SVR offers some flexibility in that it rewards the landowner who preserves existin§ trees and plants new ones with more volume. Landowners who remove exist[n§ trees to make room for expansions are subject to reduced building volumes. Once teardowns begin, tea/down proponents value regulatory flexibility. If a community's character can be retained, teardown opponents are less likety to be as adamant. The precision and flexibility of the SVR makes it easier to demonstrate the impact of various options. For example,a family may want a house with to-foot ceilin§s and a roof pitch, but the house exceeds the SVR. The relative impact of different ceiling heights or roof pitches can be instantly calculated, making trade-offs between roof, ceilings, and floor areas easier to understand. Perhaps only one room needs the higher ceiling, and the roof pitch can be retained to meet the lions. Also, adding four 12-foot-high ever- §teen trees might avoid resizin§ one room. REGULATIONS TO PRF..~ERVE COMMUNI'rf CHARACTER Identifying at-risk neighborhoods by calculating the floor area permitted within the setbacks and comparing it with existing and proposed new homes in residential d/strict5 around the community also helps planners determine deck placement and the location of other outdoor elements who's.the.building pad is full The first step is to do a maximum floor area calculation based on setbacks and then compare it to average bui[din§s, on the block. Using Did buildin§ permits or plans will make the task much easier, The second step is to compare maximum height re§ulatJons with what already exists in the neighborhood. The difference between pos- sible and existing hei§hts represents a poten- tial. character problem forthe neighborhood if teardowns occur. If the difference ts slight, and unless there are unique architectural or histori- cal characteristics involved, the impact from teardowns will be minimal. The third step is to consider the building possibilities within the setbacks. For exam. pie, is there room for decks or other outdoor accessory structures common to the neigh- 206 ZONINGPRACTICE 6.05 M~ERICAN ~LANNINO ASSOCIATION J page