HABITABLE SPACE STANDARDS FOR EXISTING ELEMENTS WITHIN ONE AND TWO FAMILY DWELLINGS

ARB-ENB-15.13

 

TOPIC: Residential Construction - UBC/3/#3 & CABO/3/#1

 

CODE: Structural Specialty Code: 1998 Edition

One & Two Family Dwelling Specialty Code: 1996 Edition

 

REVISED: March 1, 1999

 

REFERENCE: Chapter 3 - One & Two Family Dwelling Specialty Code

Chapter 3 - Structural Specialty Code

 

SUBJECT: Habitable Space Standards for Existing Elements within One and Two Family Dwellings

 

QUESTION: Are there any alternative standards which are acceptable when nonhabitable space is being converted to habitable space, or when the habitable use of a space is changing within an existing one or two family dwelling?

 

RESPONSE: This Code Guide establishes the minimum acceptable standards for changing a space to habitable space or for changes in the habitable use of a space. These standards only apply to existing elements in existing one and two family dwellings and does not apply to new construction (additions or new buildings). When designs for alterations comply with the provisions of this code guide, no administrative appeal will be required.

 

 

In habitable areas with flat ceilings, a minimum ceiling height of 6 feet 8 inches will be allowed provided that beams, heating ducts, pipes, etc may project as low as 6 feet from the finished floor. Such encroachments below 6 feet 8 inches and which are more than 2 feet from walls, shall not occupy more than 10 percent of the room area.

In bathrooms with a sloped ceiling, the ceiling height over tubs/showers and in front of toilets and basins must be at least 6 feet 8 inches.

 

An existing stairway providing access to new habitable space must be at least 30 inches wide and must have headroom of not less than 6 feet 2 inches.

 

The existing stairway must have a tread run no less than 9 inches and a riser height no greater than 9 inches. A maximum variation of 3/8 inch will be allowed between the largest and smallest rise and/or run.

 

Existing "winder" stairs, which are triangular in shape, are allowed.

 

 

Every habitable room, which does not have artificial illumination as allowed in the Exception to CABO Section 303.1, must have windows with a glass area equal to not less than 6.8 percent of the room's floor area. In basement rooms, the area of the glass in windows must not be less than 5 percent of the floor area.

 

 

Habitable rooms not provided with mechanical ventilation as per either Exception 1 or 2 of CABO Section 303.1 must have a window opening directly to the outside, with an opening area equal to at least 2.5 percent of the room's floor area.

 

 

Areas converted to bedrooms shall comply with emergency egress requirements.

 

Where an existing window is to be used for emergency egress, the window must have an opening width of at least 20 inches, an opening height of at least 24 inches and an opening area of at least 5 square feet. The window must have a sill height of no more than 44 inches above the floor.

 

Where the existing sill height of the window to be used for emergency egress is between 44 inches to 56 inches, a permanent single step, no higher than 12 inches, and extending the full width of the window, may be permanently installed provided there is a minimum of 6 feet from the top of the step to the ceiling. Windows with a sill height in excess of 56 inches shall not be used for emergency egress.

 

 

Existing double glazed windows, or storm windows over existing single glazed windows, will be accepted.

 

Where wallboard, lath and plaster and other finishes are removed from an existing exterior wall, exposed cavities must be insulated. Existing concrete exterior walls must be furred out with 2 by 4 inch framing. If there is existing insulation in the exposed cavities it can be retained provided it has a thermal value of R-11 or better. Where no existing insulation was found in exposed cavities or new cavities are created by furring out of walls, insulation of not less than R-15 value shall be installed.

 

Where finishes are removed from an existing ceiling, and in attics and garages being converted to living space, exposed areas of ceilings must be insulated to current code standards, where practical. Where ceiling height is a problem, a minimum of R-15 insulation will be accepted in existing 2 by 4 rafter spaces. Minor dormer additions may be constructed and insulated to match existing construction.

 

All roof insulation must be ventilated.

 

Updates July 1, 1996 edition

Replaces Code Guide UBC /12/#2 & CABO/2/#4

Revised March 1, 1999

Filed for inclusion in PPD September 29, 2004