Edit: I talked to a developer about the cottage impervious area scenarios, and was told that Bellevue’s Fire Department is requiring a 20′ wide driveway. For comparison, the Model Ordinance states that private driveways shall not be required to be wider than 12 feet unless there are code/life safety issues, and I think the Seattle rule is also that driveways be 12′ wide. Bellevue’s rules are in the Transportation Design Manual and there is a 20′ minimum for streets in subdivisions, a 10′ minimum for single family lots, and a 16′ paved minimum for a residential shared driveway. There is a second draft attached to the agenda for the June 24th meeting that provides the clarification that the joint driveway rules apply where there are 2 to 6 residential units on 1 or 2 lots. Sadly, this means that the scenario for cottages below doesn’t actually work, and I will have to recalculate this from scratch. I won’t remove it for now because it gives a sense of what the cottage rules might allow on a lot that’s 10′ wider than the scenario, even if the percentages will be all different. End Edit
I was in strong agreement with Mayor Robinson’s take on the cottages at the May 13th meeting that the version which would have allowed them to be 38’ tall would have too many stairs for aging in place. It is certainly an improvement that the Council voted at their June 10th meeting to cap cottage height at 24’ – compared to 22’ for Seattle cottages – though that is probably still taller than most Bellevue residents were imagining when they responded that cottages were the most popular middle housing type in the 2022 survey.
It’s also possible, however, to make cottages entirely flat, and here is an example of how the cottage loopholes could be used to put a second single family home on a lot. This would not optimize use of the FAR (it would only use 0.45 FAR, which is under the amount allowed for a single family house), but it would maximize use of the lot coverage and impervious surface loopholes. The footprint of these low cottage structures would be 36% larger than allowed for a single family house and 21% larger than would be possible for other middle housing, and the impervious area (driveways, walkways, and patio hardscape) could be about double as much as would be allowed for single family homes or other middle housing.
In order to qualify as cottage housing, the driveway would need to be counted as part of the “common open area” – the cottages would lose 12.5 sqft each from the corners so that a 15’ square could fit over the driveway and into that space, and 25% of that 15×15’ square would need to be landscaped.
Another key enabling factor is that this scenario works on a slope, so that there would be porch where the daylight basement might otherwise be, and this porch needs to be about 46% of the footprint of each cottage. In Bellevue’s proposed draft, there is no requirement that the porch face a road or a common open area or a neighboring porch – though requirements like this are common in other places that have cottage rules.
Here are four scenarios, all on the same R-5 lot
***********Single Family house ***********
R-5 minimum lot width 60’
Lot size 110 x 60 = 6600
FAR 0.5 – up to 3300 sqft
Buildable area 90 x 50
Lot coverage 40% – up to 2640 sqft, so footprint could be 50 x 52.8′
Partial second floor, maybe a daylight basement that doesn’t count against FAR
Impervious area limited to 15% above the 40% – 990 sqft
Pervious/landscaped area 45%, Tree code requirement 13 credits
50% minimum greenscape in front yard
Driveway 10 x 40’ would leave 590 sqft for patio/hardscape
*********** Pair of Cottages with Long Driveway ***********
(See feasibility caveat about driveway width above)
R-5 minimum lot width 60’
Cottage maximum size 1800 sqft each (1500 sqft + 300 sqft of bonus area)
Lot size 110 x 60 = 6600
Buildable area 90 x 50, footprints 45 x 40′ and 10’ separation
Lot coverage 54.5%
Porch area 25%
Impervious area 30.5% 2013
Driveway 10x 92’
Walkway 45 x 8
More patio/hardscape 733 sqft
Pervious/landscaped area 15% Tree code requirement 5 credits
FAR 0.55 (0.45 FAR and 600 sqft of bonus floor area)
*********** Pair of Cottages with Long Driveway and AADUs underneath ***********
(See feasibility caveat about driveway width above)
R-5 minimum lot width 60’
Cottage lot coverage 1800 sqft each, 10’ separation
Lot size 110 x 60 = 6600
Buildable area 90 x 50
Lot coverage 54.5%
Porch area 25%
Impervious area 30.5% 2013
Driveway 10 x 100’
Walkway 45 x 8
More patio/hardscape 653 sqft
Pervious/landscaped area 15% Tree code requirement 5 credits
FAR 1.1 (0.45 FAR, 1200 sqft of bonus floor area, 3000 sqft of AADU)
Building height is a limiting factor at 24’
*********** Pair of Stacked flats with Driveway and AADUs ***********
(See feasibility caveat about driveway width above)
R-5 minimum lot width 60’
Lot size 110 x 60 = 6600
Buildable area 90 x 50
Lot coverage limited to 45%
Footprints 1485 sqft each
Impervious area limited to 15%
Driveway 10x 90’
No walkway or patio/hardscape
Pervious/landscaped area 40% Tree code requirement 10 credits
Three stories: FAR 1.35, only 0.72 FAR counts against the 1.5 FAR limit
Could be FAR 1.8 if there are 4 stories, but only 1.08 FAR would count – the rest is ADU and bonus area
Building height is a limiting factor at 32’’
Condo liability laws discourage 3+ stories
- There is a separate hard surface maximum that is 75-80% for single family and 80-85% for middle housing.
- See the relevant tables on pages 6 and 30 of the draft.
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