Seattle’s 75/80 Rule for Lot Subdivision
As Platted Now
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.
Original Plat Map showing all 4000 square foot lots.
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.
For the city of Seattle’s building departments, DPD, own documentation on Single Family Zoning, here is a handy PDF File created by DPD. singlefamilydpds021570
Cliff notes for Seattle’s Single Family Zoning:
Single Family Zoning
A lot Zoned SF5000, simply means Single Family – one house per 5000 Square feet of land. Likewise SF7200 would be one house per 7200 square feet of land or lot size. Remember there are acceptations to every rule.
For SF5000, SF 7200, and SF9600 the following apply
Setbacks (in most cases):
- 5′ yard setback is required
- 20′ front setback
- 20% of lot depth for the rear setback
Building height is limited to 25′. BUT, narrow lots height can increase to 30′. Sloped lots you are allowed sloping lot derivatives and can add an additional 5′. Steep pitched (Greater then 4:12 pitch) another 5′ is granted.
- One space per dwelling unit, unless lot is less then 3000 sqft, then zero parking.
- Parking must be within the structure OR the rear or side yard. Special circumstances will allow for parking in the front yard.
- Parking entrance preferred from the alley.
- If access to parking is off then street then one 10′ curb cut is allowed per 80′ of street
In some neighborhoods, RSL, Residential Small Lot, is allowed:
- RSL – One house on a 2500 square foot lot
- RSL/T Tandum houses – two on a 5000 square foot lot
- RSL/C Cottage Housing – four houses on a 6400 square foot lot.
If you have any questions regarding zoning for your lot, please don’t hesitate to contact us.