Planning 2012-01-26 Attachment B - Memo with Attachments

Browse Search

INFORMATIONAL MEMO Page 2 establish the grade plane from the lowest ground level around the building. Another option is to allow the grade plane to be stepped to allow the structures to better respond to the topography of sloping sites. Either of these options will result in slightly lowering the maximum height of a structure on a sloping lot. In the case of the house that sparked this discussion changing the building height measuring point from average grade plane to lowest elevation would have lowered the house by about five feet. It would not necessarily prevent the construction of a third story. Setbacks Increasing the side and rear setback distance for the second and third story of a house would be another way to reduce the impact of a house on the adjacent properties. The current LDR setbacks are 20' in the front, 10' on the second front (for corner lots), 5' on the sides and 10' in the rear. Tiered side and rear setbacks that increase by 5' per story would modulate the side elevations of the houses and reduce their bulk. The increases could have the effect of limiting the development potential of smaller or oddly shaped lots and preclude the use of stock plans by developers. Another option instead of a tiered setback is to increase the rear and side yard setbacks for the entire structure and have an even larger setback for a three story house. Under this option the rear yard setback in LDR for all houses could be increased to 15 feet and to 25 feet if the house has a third story (with a possible exception for alley accessed garages or accessory structures). The house that triggered this discussion is set back 5 to 7' from one side, 8' from the other and 65' in the back. Building Footprint The LDR zone (TMC 18.10.057) currently limits the footprint of all of the structures on a site to roughly 35% (the percentage decreases as the lot size increases). The building size can be maximized by building that footprint straight up three stories. For substandard sized lots (under 6,500 sf) there is no percentage limit, only the required structure setbacks. There have been some concerns expressed with the formula in the code. Also, there have been some concerns that the formula penalizes development on larger lots or encourages square footage to be added as another story instead of expansion of the footprint. One option may be to allow administrative approval to allow variances up to 10% of the building footprint if certain standards are met such as compatibility in scale with the adjoining homes; modulation of the fagade; and /or larger than required setbacks are provided. Floor Area Ratio (FAR) Tukwila does not currently have FAR standard, which is expressed as the total square footage of the building(s) divided by the square footage of the lot. This links the size of the building to the size of the lot regardless of the number of stories. So you can choose to have 'a larger single story structure or a taller structure with a smaller footprint. Common single family residential FARs range from .45 to .65, which would limit a house on a 6,500 sf lot to between 2,925 and 4,225 sf. Tukwila's Comprehensive Plan suggests a maximum FAR of .5 not including the basement area (CP 7.6.4). The house that triggered this discussion was on a 13,500 sf lot and had a FAR of .34. One option in lieu of having a building footprint standard is to have a graduated FAR standard similar to the building footprint standard, where the percentage decreases as the lot size increases. CONCLUSION Tukwila's single family house regulations are similar to those of nearby, similarly situated communities as seen in the table in Attachment B. The common challenges with infill development are compatibility of the size /bulk with the existing homes; the street layout and orientation of the homes where not all homes face the public street; and the architecture /style of the new homes. MD 2 10 -5 -2011 W:12011 Info Memos- counciiksing leFamDevStandards.doc in