Seattle’s 75/80 Rule for Lot Subdivision
We just tried to purchase a 12,000 square foot lot zoned SF 5000, one house per 5000 square feet of land. When it was originally platted in the 1930’s it was platted as three 4000 square foot lots. But, somebody built a house straddling two of the lots in the 1960’s. We had a meeting with DPD, took all the neighbors lot sizes to the meeting, and the decision was made since the house is straddling two lots, the two 4000 square foot lots have been combined. So we are left with one 4000 square foot lot, and one 8000 square foot lot. The question is, can we re-subdivide the lots back to the original 4000 square foot lots? Answer, No. See below.
DPD has a 75/80 rule that will allow you to short plat lots into parcels less then 5000 square feet. (SMC 23.44.010 B.1.a)
1) The new lot/lots created must be 75 percent of the general minimum lot area for the zone.
2) At least 80 percent of the mean area of the lots on the same block face and within the same zone.
5000 square foot lot x 75% = 3750 square foot lot is the smallest allowed.
IF 80 percent the mean of the neighbors lots is 3750 or less.
Neighbors lots: 5000, 4400, 4000, 6000, 5300, 5500, 4000 = 34,200/ 7 lots = 5520 * 80% = 4,886 square feet is the smallest allowed on this block.