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The City of Portland, Oregon

Development Services

From Concept to Construction

Phone: 503-823-7300


1900 SW 4th Ave, Portland, OR 97201

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Special Standards for Attics, Basements and Garage Conversions

To make conversions easier, the Bureau of Development Services has set up the following special standards for existing situations. These standards apply only to conversions that would increase livable space in the existing dwelling, not those that would add a dwelling unit on the property.

More information on converting attics, basements and garages to living space.
Ceiling Height in Basements, Attics and Bathrooms
In basements, existing ceiling heights lower than 6'8" will not be approved. However, beams, heating ducts, pipes, etc. may be allowed as low as 6 feet from the proposed finished floor within 2 feet of an exterior wall and not crossing a doorway or hall.

In attics and half stories, the ceiling height may be a minimum of 6'8" if it is over an area no smaller than 6' x 10', and if it is at least 5 feet high over an area no smaller than 10' x 10'.

In bathrooms with sloped ceilings, the ceiling height over tubs and showers and in front of toilets and basins shall be as follows:
  • Immediately in front of the toilet and basin, ceiling height shall be 6'6" minimum.
  • Over tubs, the ceiling height shall be a minimum of 6'6" for an area of 30" x 48" or 80 percent of the area of the tub, whichever is greater. Sloped ceilings within the tub area shall not reduce ceiling height to less than 5'9" at any point.
  • In showers, the ceiling height shall not be less than 6'6" for an area of 1.024 square inches or 80 percent of the shower area, whichever is greater. Sloped ceilings within the shower area shall not reduce ceiling height to less than 5'9" at any point.
  • Sloping ceilings of 6'2" minimum height are allowed at stairs and landings.

Emergency Egress Windows
  • Basements and sleeping rooms, which do not have a door leading directly to the outside must have a window large enough to allow escape or rescue in case of an emergency
  • The windowsill height must be 44" or less. A single step, no higher than 12" and as wide as the window, may be permanently installed in order to reduce the sill height to 44" or less, provided there is a minimum of 6 feet from the top of the step to the ceiling
  • An existing window opening used for emergency egress must have a width of at least 20", a height of at least 22" and at least 5 square feet of area that can be opened. New egress windows may have to have a larger opening area
  • View more information on windows

  • If you are building a new stairway, it will need to meet current code requirements
  • An existing stairway leading to new living space may be steeper, narrower and may have lower headroom than the current code allows However, it must be at least 30 inches wide and must have headroom of 6'2" or higher, including landings
  • The stairway must have runs no smaller than 9 inches and risers no higher than 9 inches. The steps should be relatively even. A difference of more than 3/8" between the biggest and the smallest rise or run will not be approved
  • Existing winder stairs, which are triangular in shape, are allowed. New winder stairs must meet current code
  • View more information on stairs

Insulation and Ventilation
In general, additions that increase the floor area of the house must be insulated as though for new construction.
  • New windows or doors must meet current code requirements for energy conservation.
  • Existing double glazed windows or storm windows placed over existing single glazed windows will be approved.
  • If the wallboard, lath and plaster, or other finishes are taken off the wall or ceiling, then the open areas must be insulated. Also, if the walls or ceilings can be insulated without removing finishes, then insulation will be required.
  • Existing concrete exterior walls must be furred out with framing sufficient to accommodate the required insulation. Any wood in contact with concrete must be pressure treated wood.
  • When new construction affects basement walls, they must be insulated to current code. Existing insulation in basement walls that is R-11 or greater will be approved.
  • Attic and garage ceilings must be insulated to current code. When ceiling height is a problem, R-15 minimum insulation will be approved in spaces between existing 2" x 4" rafters. Minor dormer additions may be constructed and insulated to match the existing construction.
  • If you will be raising the garage floor by installing new wood floor joists over existing concrete, then insulation and a vapor barrier must be provided in the joist space.
  • Roof ventilation is required, install the appropriate number of roof vents for your project.
  • Verify combustion air requirements for all fuel burning appliances.
  • Natural ventilation openings may be required in a quantity not less than 2.5 percent of the floor area.
Visit the Plan Review staff at the Development Services Center or call (503) 823-7310 for more information on Special Standards.