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City of Mill Valley Residential Design Guidelines

The City developed these Residential Design Guidelines to facilitate appropriate and environmentally sensitive development review. As design proposals take shape all interested parties shall use these Guidelines to better communicate concerns, set expectations and meet goals within organized, clear and balanced parameters.

Design is a complex process balancing many issues. These Guidelines try to balance the immediate wishes and rights of a homeowner/builder with long-term responsibilities to the community and environment. They reflect a commitment to the sustainability of Mill Valley. These Guidelines are based on an approach that takes into consideration the interrelationship of individual houses with the neighborhood; the relationship of one neighborhood to another, and with the way each of these components affect the environment. The Guidelines convey the idea that the whole is greater than the sum of its parts.

These Guidelines implement the goals and policies of the Mill Valley General Plan. They also supplement the Mill Valley Municipal Code, which contains more technical and specific development standards. They are not intended to be rigid regulations, nor are they intended to promote a particular type of design. Variations from these guidelines may be appropriate when weighed against other considerations. Compliance with any particular guideline does not override the intended balance that an appropriate solution should reach.

The guidelines are listed and then described in more detail below. For a PDF version of the guidelines, click here

Slope Design Guidelines
Guideline 1 - Integration with Topography
Guideline 2 - Relationship of Building Size to Slope                                                

Flora and Fauna Design Guidelines
Guideline 3 - Protection of Existing Vegetation & Habitat
Guideline 4 - Plant Material & Compatibility with Setting
Guideline 5 - Minimizing Water Use
Guideline 6 - Privacy and Views
Guideline 7 - Tree Replacement
Guideline 8 - Fences
Guideline 9 - Minimizing Fire Hazards 

Soils and Grading Design Guidelines
Guideline 10 - Minimizing Grading, Offhaul, Excavation & Erosion
Guideline 11 - Retaining Walls
Guideline 12 - Minimizing Landscape Terracing                 

Drainage Design Guidelines
Guideline 13 - Site and Building Drainage

Building Design Guidelines
Guideline 14 - Energy Conservation Measures
Guideline 15 - Sustainable Design Principles
Guideline 16 - Fire Resistant
Guideline 17 - Scale, Mass and Height
Guideline 18 - Color
Guideline 19 - Windows, Roofs, Skylights and Roof Mounted Equipment
Guideline 20 - Driveways
Guideline 21 - Parking Standards, illustration  (See 20.60 Section of the municipal code for additional details)
Guideline 22 - Exterior Lighting

Description of Guidelines

SLOPE DESIGN GUIDELINES:
Guideline 1 - Integration with Topography
New residential buildings and additions to existing residential buildings constructed on sloping land should be designed to relate to the existing landforms in order to minimize the building’s mass and bulk and integrate the building with the site (for example, step with the slope).

Guideline 2 - Relationship of Building Size to Slope
Slope conditions can exaggerate height, bulk and mass. A building shall be in scale with its surroundings. Special attention shall be given to minimize the height, bulk and mass on steep sites. When a lot has steep slopes, F.A.R. may be substantially reduced to mitigate impact. (See Mill Valley Municipal Code Section 20.66.045)

Guideline 3 - Protection of Existing Vegetation and Habitat
Development plans shall maximize the amount of land retained in its natural state. Where appropriate, residential projects should be designed to preserve, protect, and restore native site vegetation and habitat. Particular consideration should be given to protection of systemic groups of native vegetation such as established groves, sapling clusters or riparian zones. Construction activities including grading, stripping, compaction, parking, storage of materials, and wash-out are discouraged in the drip circle of a significant tree or an area group of vegetation or riparian zone. Protected trees are to be clearly marked and temporary fencing shall be used to delineate any significant areas.

Guideline 4 - Plant Material Selection and Compatibility with Setting
Landscape designs should incorporate the existing native vegetation and integrate new native planting with the existing planting, where appropriate. Landscape plans for residential development should be compatible with the character of the site. Plans should focus on restorative efforts to replenish native species and complement preserved existing vegetation. In more natural locations, the design should be integrated with the natural setting. Landscape plans for residential development should include a mix of fast and slow growing plant materials. Trees that tend to break in high winds should not be planted. Plants that are pyrophytic or tend to spread rapidly crowding out natives should not be planted.

Guideline 5 - Minimizing Water Use
To the extent possible with other design considerations, drought tolerant planting selections and designs are encouraged. Landscape plans shall comply with the current water conservation regulations of the Marin Municipal Water District and should include water conserving irrigation systems, such as drip irrigation, low flow sprinklers and automatic controls. While irrigation will probably be required initially in order to establish the new plants, the plant material should be selected so that once established, much of the major site landscaping could survive on rainfall. Turf areas should be minimized, because of their high water and chemical requirements.

Guideline 6 - Privacy and Views
Development should include appropriate landscaping to maximize privacy between residences. Landscape plans should provide appropriate planting to screen or soften any undesirable light pollution or views from off-site. Landscape plans should include appropriate planting to soften the appearance of new construction as seen from off-site locations. Screening landscaping should not substitute for good architectural design. Landscape plans should take into consideration the future impact the new planting may have in obstructing views from existing adjacent and distant dwellings. Landscape plans should include appropriate screening for unattractive views of building and site elements, including but not limited to, building foundations, deck supports, trash collection or parking areas, that cannot be mitigated through architectural design. Applicants are not required to unreasonably compensate for inadequate landscaping on adjacent sites.

Guideline 7 - Tree Replacement
When approved for removal and/or lost during construction activities, trees that define the nature of the site, not determined to be dead or diseased, should be replaced as appropriate as a part of an approved landscape plan. Replacements should be as approved and/or directed by a city arborist, certified arborist or landscape architect to aid in soil stability, provide necessary canopies and/or screening, and enhance the unique visual landscape character of Mill Valley.

Guideline 8 - Fences
Fences are discouraged within the public right-of-way and exterior yard setbacks and where they change the existing neighborhood character. Fences should be designed and located to neither block vehicle and pedestrian sight lines nor inhibit collectively the “through neighborhood” travel of wild animals. Fences should be setback from community amenities such as streets, trails, creeks, intermittent waterways, and open space or parks. Fences should be designed to be compatible with that of the residential buildings and aesthetically attractive or transparent.

Guideline 9 - Minimizing Fire Hazards
Plant materials should be selected to minimize fire hazards to residential buildings. The landscape plans should be reviewed by the Fire Department and appropriate “greenbelting” landscaping should be incorporated into the plan. Plants that are pyrophytic, such as Acacia, Scotch Broom and Eucalyptus, should not be planted (a list of pyrophytic and fire resistant plants is available from the Planning Department).

SOILS and GRADING DESIGN GUIDELINES:
Guideline 10 - Minimizing Grading, Offhaul, Material Import, Excavation and Erosion:
Projects should be designed to minimize cut and fill areas and material import and offhaul. Material import and offhaul are discouraged especially in locations of limited or difficult access. In particular, projects that include new basements should be designed to minimize net cut offhaul and material import. The preferred basement has a cut of no more than 100 cubic yards and a ceiling height of 7 ½ feet. However, a larger or smaller basement may be allowed depending on the nature of the site and the amount of offhaul.

Special care should be taken to final grade all disturbed areas to a natural appearing configuration. Where grading is necessary and retaining walls can be avoided, site terracing should be utilized so that no vertical cut exceeds 5 feet and no horizontal step is less than 3 feet. Due to the larger surface and sub-surface disruption caused by site terracing and/or grading, revegetation of these areas is required. Grading should be minimized near or within the dripline of significant or designated protected trees.

Guideline 11 - Retaining Walls
Low retaining walls are encouraged where their use would minimize uphill cutting. Large single plane retaining walls shall be avoided. Wherever possible, stacked and stepped landscaping elements should be utilized in lieu of planar walls. The maximum height of any single plane retaining wall exposed to public view should not exceed eight feet. Cut banks higher than eight feet shall have stepped retaining walls. Concrete walls exposed to public view shall be textured and/or colored to match adjacent soil or plant color or have an approved architectural finish.

Guideline 12 - Minimizing Landscape Terracing
Landscape designs should not rely on extensive terracing of land to accommodate uses such as pools, sizable lawns, tennis courts or patio areas. Land terracing may be considered where it will integrate development with the topography in a more satisfactory way than raised platforms and decks.

DRAINAGE DESIGN GUIDELINES
Guideline 13 - Site and Building Drainage
Storm water runoff shall be maintained in its natural path. To the greatest extent possible, impervious surfaces shall be minimized and mitigated. Each site should be final graded so that no concentrated water caused by improvements flows onto an adjacent property, but instead is dissipated for natural percolation or directed toward a street or storm drainage facility. Stormwater facilities will be designed to divert surface water away from cut faces or sloping areas of recent excavation. Flow retarding devices, such as detention ponds and re-charge berms, are encouraged where practical to limit the volume and rate of storm water runoff. Changes in hydrology and site drainage should be minimized within the dripline of significant or designated protected trees. Buildings, particularly in hillside locations, should be designed to minimize impact on or alteration to natural drainage and absorption rate patterns. To the extent possible with other design considerations, building designs should not degrade rainwater or run-off, inhibit groundwater absorption and underground flow, or accelerate or otherwise concentrate any re-directed flows.

BUILDING DESIGN GUIDELINES
Guideline 14 - Energy conservation measures
Buildings should be designed to meet or exceed the current California Energy Commission standards. The use of methods to reduce energy consumption is encouraged. Design and location of solar panels should be consistent with other design considerations.

Guideline 15 - Application of Sustainable Design Principles
Development should be efficient. To the extent consistent with other design considerations, designs should be creative and innovative in their use of materials and methods to minimize resource consumption. Materials should be considered which protect the natural environment from long-term harm. To the extent possible, materials should be used which are long-lived and use minimal energy in their manufacture, have high recycled content, and minimal non-renewable material content. Building materials and finishes should minimize the visual impact of the development. Large areas of building materials that reflect light towards existing homes should be avoided.

Guideline 16 - Fire Resistant
Buildings should be designed to be fire defensive. Designs should minimize risk of fire by a combination of both architectural and landscape attributes, including, but not limited to, the use of fire resistive building material, fire sprinklers, noncombustible roofing, and defensible landscaping space.

Guideline 17 - Scale, Mass and Height
All buildings should be designed to avoid monumental or massive buildings that are out of scale with their setting and detract from the neighborhood character. Buildings should not have large expanses of a material on a single plane. Sizable roof overhangs (exceeding the requirement for sunscreening), decks and upper story cantilevers should be avoided if the resulting building form unnecessarily increases the bulk of the construction. Buildings should be located and designed to minimize the obstruction of any ridge silhouette when viewed from off-site locations.

Guideline 18 - Color
Buildings and site work should utilize colors that minimize the visual impact of development, blend with the existing land forms and vegetative cover, are compatible with others in the neighborhood, and do not attract attention to themselves. All colors shall be selected to minimize contrast and glare.

Guideline 19 - Windows, Roofs and Skylights and Roof Mounted Equipment
Window and skylight size, placement and design should be selected to maximize the privacy between adjacent properties. To the extent consistent with other design considerations, the placement and size of windows and skylights should minimize light pollution and/or glare. All roofs shall consist of non-combustible, non-reflective materials chosen to be compatible with the surroundings. All roof penetrations and roof mounted equipment shall be compatible with the roof color. Where visible from off-site locations, skylights should be flat lens.

Guideline 20 - Driveways
Driveways should be designed to provide safe access, ease of grade, minimize grading and/or retaining walls, and protect water quality. To minimize collection and concentration of pollutants, consideration, when feasible, should be given to design driveways so they drain onto adjacent turf or groundcover areas, or other permeable landscape, in order to disperse and cleanse pollutants. The maximum slope of new residential driveways should not exceed 25 percent and all driveways with greater than 15 percent slope should include a non-slip finish. Driveways and walkways should be designed to follow as closely as practical the natural contours of the property. Driveways constructed of permeable materials are encouraged. The use of brick or unit pavers on sand, or concrete only under wheels, is encouraged for flat sites. All driveway designs will require review and approval by the Fire Department.

Guideline 21 - Parking
As provided in Municipal Code section 20.60.090, all new homes shall have a minimum of two on-site parking spaces plus one on-site space for guest parking when on-street parking is not available along the immediate frontage of the property, and one on-site space for each roomer. One of these spaces may be of compact car size. Care should be taken not to locate parking in a manner that might allow vehicle chemicals to contaminate natural run-off. All garages with less than a 20 foot setback from the edge of the street should have automatic doors.

Guideline 22 - Exterior Lighting
Appropriate night lighting may be provided for security and safety. Both construction and permanent exterior lighting should be designed to conserve energy and to eliminate glare or annoyance to adjacent properties or public areas. Primary light sources should be shielded and directed downward. Lamps should be of a minimal wattage and have a warm light color.

Last updated: 11/3/2015 9:17:52 AM