Residential drafting in Happy Valley, Oregon
Happy Valley is the newest housing stock in our Oregon coverage. Most of it is recent master planned construction with large footprints, and the houses are frequently built out close to the maximum lot coverage the zone allows.
That is the central constraint. On a lot where the house already uses most of the allowance, a new detached building may not fit even though the yard looks generous. Interior conversion or an attached addition is often the only workable path, and establishing that early saves a design cycle.
Sites are steeply graded in places, terraced with large retaining walls to capture views. Slope brings engineering, drainage, and access questions, and hillside wind exposure affects shear wall detailing.
ADU standards
Setback, size, and parking rules for an accessory dwelling unit in Happy Valley.
| Maximum size, attached | No more than 50 percent of the house's gross habitable floor area (HVMC 16.44.050(B)(4)) |
|---|---|
| Maximum size, detached | 50 percent of the house or 1,000 sq ft, whichever is less (HVMC 16.44.050(B)(4)) |
| Measuring the house | An attached garage is excluded from the house's floor area for this calculation (HVMC 16.44.050(B)(4)) |
| Setbacks | The underlying residential zone standard (HVMC 16.44.050(B)) |
| Reduced setback | 3 ft side or rear, available only at 200 sq ft or less and 14 ft or under (HVMC 16.44.055(C)(1)(b)) |
| Height, detached | The higher of 50 percent of the house's height or 26 ft (HVMC 16.44.050(B)(3)) |
| How many | One per parcel (HVMC 16.44.050(B)(1)) |
The size rule here is stricter than the state floor and stricter than the neighboring cities. The unit is capped at half the house's gross habitable floor area, and a detached unit is additionally capped at 1,000 square feet (HVMC 16.44.050(B)(4)). On a 1,600 square foot house that means an 800 square foot maximum, not 1,000.
The house's attached garage is excluded when calculating that 50 percent, which makes the allowance smaller than a quick measurement suggests.
There is a three foot reduced side or rear setback, but it only applies to a structure of 200 square feet or less and no taller than 14 feet (HVMC 16.44.055(C)(1)(b)). That is a garden studio, not a dwelling with a kitchen and a bathroom, so most projects take the district setbacks.
For short term rental, Happy Valley requires the property to be the owner's primary residence.
Planning office: Happy Valley Planning Division
Sources: Happy Valley Municipal Code 16.44.050, 16.44.055. Ordinance 592, adopted June 2025. ORS 197A.425. Last checked August 2026.
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