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2 1 2 W K I N Z I E • S U I T E 3 0 0 • C H I C A G O , I L L I N O I S • 6 0 6 5 4 P H O N E : 3 1 2 5 2 7 2 5 0 0 • F A X : 3 1 2 2 6 8 7 4 1 8 M E M O R A N D U M Date: August 20, 2009 To: Roger Millar, Director, Missoula Office of Planning and Grants From: Kirk Bishop Subject: Hillside Height In recent weeks, I have been working with Laval and Tom to understand and respond to various points of view on the issue of regulating/measuring building heights in hillside protection areas. It is my understanding that three basic approaches have been discussed, as follows: 1. The so-called “tabletop method” contained in the planning board recommended draft zoning ordinance. Under this method, building height is measured from the lowest point where the building line meets existing or finished grade (whichever is lower) to the highest point of the subject building, excluding chimneys and similar features (see illustration, below). 30 ft 10% slope 15% slope 25% slope Hillside Height Measurement “Table Top” Option Side view - 5,400 sq ft lot 90 X 60’ Two-level 50 x 45’ house (4,500 sq ft+ ) 90 ft lot length 30 ft 50 ft 30 ft 50 ft 50 ft Existing grade Building Envelope - imaginary plane that extends between the uphill and downhill points ---PAGE BREAK--- – 2 – August 20, 2009 2. The “envelope” method, under which all portions of a building (except for chimneys and other minor exceptions) must fit within the envelope created by two imaginary, parallel, planes—one generally following the ground slope beneath the building and one located 30–35 feet above that lower plane (see illustration, below). 3. The “tapered envelope” method, which is identical to the “envelope” method except that the top imaginary plane tapers down on the uphill end rather than running parallel to the lower plane (see illustration, p. Our original draft ordinance recommended use of the so-called “tabletop” method for all properties—flat lands, hillsides and everything in between. This recommendation was based on our belief that the new ordinance should include a uniform, predictable, reasonable and transparent formula for regulating and measuring building height. We continue to believe that the building height measurement method presented in Sec. 22.110.060 of the proposed ordinance is the right approach…citywide. It will, we believe, be easiest to measure and administer. It is transparent, predictable and intuitive in that it treats all parts of the building the same, except for minor vertical projections such as chimneys and antennas (as opposed to the current approach of measuring only halfway up a pitched roof, as if the top portion of the roof was invisible). While this recommended approach is certainly not liberal, it does seem reasonable. It will require that some buildings on some sites be “stepped” to follow the slope of the site and may pose an obstacle to some building types/designs in hillside areas, but existing (5-foot) allowance for additional building height for steeply pitched roofs and the ever-present possibility of obtaining relief through the zoning variance process should help mitigate those concerns. 30 ft 10% slope d d h i h 15% slope 25% slope Hillside Height Measurement Envelope Option Side view - 5,400 sq ft lot 90 X 60’ Two-level 50 x 45’ house (4,500 sq ft+ ) 90 ft lot length 30 ft 50 ft 30 ft 50 ft 50 ft Existing grade Building Envelope - imaginary plane that extends between the uphill and downhill points ---PAGE BREAK--- – 3 – August 20, 2009 30 ft 10% slope 15% slope 25% slope Hillside Height Measurement Tapered Envelope Option Side view - 5,400 sq ft lot 90 X 60’ Two-level 50 x 45’ house (4,500 sq ft+ ) 90 ft lot length 30 ft 50 ft 30 ft 50 ft 50 ft Existing grade Building Envelope - imaginary plane that extends between the uphill and downhill points 24 ft 24 ft 24 ft • Existing: one story daylight basement • 2320 sq ft main floor, 840 sq ft garage • zone RR-I, 30 ft height limit (6/12 roof pitch) Hillside Height Measurement 16% Slope Example 35 ft Title 20: •Hillside standards apply •Structure fits within new measurement technique 30 ft Table Top Envelope Tapered Envelope Existing grade ---PAGE BREAK--- – 4 – August 20, 2009 Title 19: Envelope Method • Existing: Split level, daylight basement • 2940 sq ft main floor + two 600 sq ft garages • zone RLD-2, 30 ft height limit (6/12 roof pitch) Hillside Height Measurement 11% Slope Example 30 ft Title 20: •No longer required to apply hillside standards •Building height remains 30’ Title 20: Table-top method 24 ft Tapered Envelope Method