Code Analysis

Project Name: Snohomish Carnegie Library

Location: 105 Cedar Street, Snohomish, Washington

 

Description of Proposed Project

The Snohomish Carnegie Library is located within a designated Historic District and is a local landmark. Rehabilitation of the existing, 1910 era, concrete and wood frame Carnegie Library building to allow for a change of use for community gathering, and provide universal access. Work will include removal of an entry lobby and a portion of the addition on the south side of the Carnegie, both of which were added in 1968, and construction of a new, enclosed back exit stair. Interior spaces will be rehabilitated for community use, with provision of a new elevator and required exits, and restoration of the original main entry and exterior wall finishes. System upgrading will include heating and ventilation, plumbing and electrical, seismic and structural systems, provision of fire sprinklers and alarms, and a security system. The site will be rehabilitated with new terrace and restored landscaping. Remaining portions of the one-story 1968 south addition will be provided with a new north perimeter wall and entry. Hazardous materials will be abated as part of the necessary demolition.

 

Building Code: International Building Code, 2003 Edition

Local Authority: City of Snohomish Title 19

 

Existing Gross Areas:

Current Site: Carnegie Library: 1968 Addition: Total:

30,732 Gross Square feet (GSF) 4,585 GSF, First Floor, Mezzanine, Basement, East Stairwell 5,088 GSF (lobby, office, toilet/mech., hall and gallery) 9,673 GSF

 

Proposed Net Areas:

(Areas are measured inside 10" and 12" wide concrete walls, with 4" added for furring and insulation.)

Carnegie Library, Gross: Carnegie Library, Net: Separate 1968 Addition:

2,345 GSF, Footprint (35.92' x 60.33' + 19.58' x 9.08') 4,690 GSF, Total, Two Floors 1,902 Square feet (SF), First Floor 146 SF, Mechanical Mezzanine (no occupancy) 1,948 SF, Basement 150 SF, New Stair Addition 4,102 SF Total 3,425 SF (Entry, Hall, Toilet/Mech. Rm. and Main Space, after demolition and removal of 1,663 square feet)

Proposed Occupancy

The Carnegie Library building will have a new function, with a change of use and an occupancy group defined by the IBC: Section 303, is for Assembly Group A., "Assembly spaces for civic or social functions, recreation, food or drink consumption." A room or space used for assembly purposes for fewer than 50 persons and accessory to another occupancy shall be included in that occupancy. Assembly areas with less than 750 SF, which are accessories to another occupancy, are not assembly occupancies.

The code identifies different assembly uses in A-1, A-2, and A-3 groups:

A-1 Assembly uses, usually with fixed seating, for theaters, concerts, cinemas

A-2 Assembly uses, for food/drink consumption, such as banquet halls

A-3 Assembly uses, for recreation, art exhibits, community halls, dance halls

Section 304, B Business, may be selected for offices and classrooms above 12 th grade

A-2 and A-3 Assembly Groups both describe the proposed program. The A-3 occupancy group is for unconcentrated use, such as with tables and chairs. However, based on reviews with the Snohomish Building Code Official, an A-2 Occupancy has been selected as it is consistent with Title 19 the total proposed number of occupants, which is over 100 people.

 

Required Separation

Occupancy separations are required between different uses. However, the entire building is proposed as an A-2 Occupancy.

 

Construction Type

Construction Type is Type V (non-rated) by virtue of its wood framed roof structure (IBC Table 601). Other materials include:

Exterior: Non-combustible, 10" and 12" reinforced concrete walls

Interior: Wood framing and posts

Roof: Wood trusses (with skipped roof sheathing and clay roof tiles)

Flooring: Wood at First Floor

 

Allowable Area Calculations

Table 503 indicates that A-3 occupancy is allowed in one-story buildings of up

to 40' tall, and up to 6,000 SF for Construction Type V. The Carnegie Library is an estimated 37' tall, from grade to top of roof ridge. It is a one-story building with a basement, and the proposed size is 4,011 GSF, both within the allowable limits.

 

Occupant Load

(IBC Table 1004.1.2. A-2 uses at First Floor includes the Main Room and two

small wings, which together total 1,483 SF +107 SF entry = 1,590 SF/15 persons = 106 maximum occupants. There is no proposed occupancy at the Mezzanine. A-3 at the Basement includes the occupied Meeting or Classroom of 848 SF and a Kitchen of 107 SF = 1,055 SF/15 persons = 64 maximum occupants. (No occupants are calculated for the Basement corridor, storage and service spaces).

Total proposed occupants = 106 + 64 = 170

 

Req. Exits

Two exits are required for each floor with A Occupancies with more than 50 occupants (Section 1014). Thus two exits will be required at each floor.

 

Egress and Stair Requirements

Based on calculations using the number of occupants, the total minimum width of exits is less than 30". However, width of egress spaces will be greater than that for functionality, comfort, and to meet code and ADA requirements. The minimum width of the back exit stairway width is 48".

ADA and other exit requirements will govern door widths. (Doors may encroach up to 7" into the egress travel route, such as an exit hall.) Stair risers must be 7"h. maximum and treads 11" d. minimum. A place of refuge at each floor is provided within the back exit stairwell.

 

Access & ADA, Chapter 11, and City of Snohomish Title 19

When there is a change of use, at least one accessible building entrance is required, and at least one accessible route of travel must be provided from the entrance to the primary function areas. An accessible passenger-loading zone is required when there are such zones, and one accessible route to assessable parking is required. Alterations must comply with Chapter 11 for access. Allowances are provided in Chapter 34 of the 2003 IBC, Section 3409.8, for Historic Buildings with 1:12 ramp slopes except where there are space limitations, when slopes of 1:10 and 1:8 are allowed with maximum ramp rises of 3" to 6". In Chapter 34, historic buildings with ramps that have a total rise of less than 24", slopes may be steeper, up to 1:8. However, the City of Snohomish has not adopted Chapter 34, and governs historic buildings with the City of Snohomish Title 19 requirements. Thus the accessible ramp is sloped at 1:12 throughout its length.

 

Required Plumbing Fixtures, Chapter 29

Based on 170 maximum occupants, with 50% or 85 male and 85 female:

Water Closets: Male: 1 WC per 125 (85 persons) = 1 Water Closet

(One urinal is also proposed)

Female: 1 WC per 65 (85 persons) = 1.3 = Water Closets

(For functionality two water closets are proposed)

Lavatories: 1 Lavatory per 200 (85 occupants) = 1 Lavatory each, M&F

Drinking Fountain: 1:500 occupants = 1 drinking fountain

Service Sink: 1 service sink