Bookstacks can occupy over 50% of a library’s space (Siems & Demmers, n.d.). Therefore, calculating space allocation for shelving and shelving capacity are an integral part of any library renovation or construction. Shelving height, depth, material, placement and accessories are all factors in the overall appearance and function of a library. Shelving systems must be designed and installed to keep patrons safe and aid in the preservation of materials.

## Space AllocationChildren's shelving, low height and colorful; Obtained from flickr.com under the terms of the Attribution 2.0 Creative Commons License.

“One of the keys to the success of any library project is to provide enough shelving to meet the requirements for planned collections” (Siems & Demmers, n.d.). Planners must consider both the shelving capacity of individual shelving units and the overall square footage needed for shelving. To calculate shelving capacity, one can use a simple mathematical equation based on the average number of volumes per shelf or take advantage of software applications such as Libris Design, which can calculate shelving requirements for specific collections. Regardless of the method of calculation used, the criteria used to calculate shelving requirements are shelf capacity, shelf depth, stack height, number of shelves per unit, the use of single or double sided shelves and aisle width (Siems & Demmers, n.d.).

## Shelf Capacity and Shelf Depth

Shelf Capacity is the number of volumes capable of being shelved on a linear foot of shelf. Standard bookstacks are 90” high by 36” wide and have 7 shelves. Therefore a typical shelf has 3 linear feet of storage. The number of volumes that can be stored per shelf varies depending on the material. For example, references books take up more space than fiction books.

Shelf depths range between as little as 6 inches for some AV materials to 16 inches for flat newspaper storage or oversize books. Standard shelf base depths are 8 inches (rarely used today), 10 inches (most common) and 12 inches (for Reference, Easy picture books & flat periodical storage) (Bryan, 2007) (Siems & Demmers, n.d.). Average volume size and recommended shelf depth for various media types have been calculated to aid libraries in their calculations:
Volume Type
Recommended Depth (inches)
Volumes per Linear Foot of Shelf
Encyclopedias
12
6
Fiction
10
8
Large Print
10
8
Non-Fiction
12
10
Paperbacks
8 to 10
16
10
12
Children's Picture Books
12
20
Juvenile Fiction
10
13
Juvenile Non-Fiction
12
13
Audio CD/CD Rom/DVD
8 to 10
30
Magazines
12
1
Newspapers
12
1
Using the average units per linear foot of shelf for fiction (8), the equation for the capacity of a single facing shelf is:
8(volumes per linear foot) x 3(linear feet) x 7(shelves) = 168 volumes of fiction

It is important to keep in mind that stacks can be single faced or double faced. A double facing unit can hold twice the number of volumes and will
 Cantilever-style shelving, no canopy top or end panels; Obtained from flickr.com under the terms of the Attribution 2.0 Creative Commons License.
take up twice the square footage of its single facing counterpart. Also, just because one unit has the capacity to be filled with 168 volumes does not mean it should be. Working collections require shelves that are between 70 to 75% capacity to allow for collection management, re-shelving and new acquisitions (Siems & Demmers, n.d.).

## Stack Height

Common standard heights are 42”, 66”, 84” or 90” high. The height of each stack depends on the materials being housed and will also determine the number of shelves per unit. Units hold between two and seven shelves per side. Materials for young children should be in lower shelves. Large print collections should reflect the needs of the elderly and visually impaired by not being too high or too low. Library planners should keep in mind the need for supervision of a given area as shelves that are 66” and higher block sight lines (Siems & Demmers, n.d.).

Here are the Recommended Unit Height for various materials:
Reference 66” (2 to 4 shelves)
Adult Fiction 90” (7 shelves)
Adult Non-Fiction 90” (7 shelves)
Children’s Picture Books 42” (3 shelves)
Juvenile Fiction/Non-Fiction 66” (5 shelves)
Young Adult 66” (5 shelves)
Large Print 66”/78”
Current Periodicals 45”/66”
(Bryan, 2007)

Shelf Height recommendations for school media centers:
Elementary Schools 42” and 60”
 Cantilever-Style Shelving, with canopy top, end panels & signage; Obtained from flickr.com under the terms of the Attribution 2.0 Creative Commons License.

Middle/Jr. High Schools 60” and 82”
Senior High Schools 60” and 82”
(Klasing, J.P., 1991).

## Aisle Width

Along with width and depth of shelving, the aisle space between stacks is the third factor is determining the space allocating for each unit. Net square footage for shelving includes not only the footprint of the shelving unit itself, but also space around it. The width between rows of shelving must be the minimum ADA requirement of 36”, although the ADA-preferred width is 42”. It is important for library planners to also check local and state regulations that may require an even wider aisle. Libraries must also decide how many shelving units are used to make up one row. Many public libraries limit the number of units per row to five to make it easier for users to find materials (Bryan, 2007).

The following square footage is required for single-sided shelving (multiply by two for double-sided):
36” Aisle Width
Base Shelf 10” 8.75 square feet pet unit
Base Shelf 12” 9.40 square feet pet unit
Base Shelf 15” 10.3 square feet pet unit
 Cantiliver-style shelving, with periodical display. Obtained from flickr.com under the terms of the Attribution-Non commericial-NoDerivitative Works 2.0 Creative Commons License.

Base Shelf 18” 11.25 square feet pet unit

42” Aisle Width
Base Shelf 10” 9.70 square feet pet unit
Base Shelf 12” 10.30 square feet pet unit
Base Shelf 15” 11.25 square feet pet unit
Base Shelf 18” 12.20 square feet pet unit
(Library Administration & Management Association, 2001)

## Shelving Types

Cantilever-style Steel Shelving
Cantilever-style, or bracket, steel shelving is the most widely used for book and multimedia storage and display (Siems & Demmers, n.d.). “Cantilever-style steel shelving uses a heavy-duty, slotted, vertical (upright) support column, supported by an appropriate load-bearing base structure, from which shelves can be bracket attached to form single-faced or double-faced shelving units. The uprights have elongated holes or slots in one-inch increments to allow for the easy adjustment and relocation of the shelves” (Siems & Demmers, n.d.). They come in the standard widths and heights mentioned above or custom heights can be made using the adjustable vertical support column.
 Case-style Shelving; Obtained from flickr.com under the terms of the Attribution 2.0 Creative Commons License.

Cantilever-style shelf accessories:
• Canopy Tops: Wood, particle board or metal top that can act as a design feature, additional storage or workspace and protects books from dust.
• End Panels: wood or metal end panel on the end units. Acts as a design feature and to allow for necessary signage.
• Book Supports/Divider shelves: In addition to standard metal or plastic book ends, some cantilever shelving is designed to accommodate wire book ends that attach to a movable track on the shelf. There are also metal dividers available that fit into slots on the surface of the shelf.
• Filler Units: panels that fill in architectural voids such as when two shelves meet in a corner.
• Signage: Signage informs the library user of the range of books and/or the subject contained on a bookstack.
• Media specific accessories include multi-media browser bins, retractable reference shelves, newspaper shelves & periodical displays.
• Lighting: Light fixtures can be attached to bracket shelving to act as display-type lighting for a single shelf, to illuminate the entire stack or provide additional lighting to the aisle.

Case-style Shelving
 Compact moveable shelving; Obtained from flickr.com under the terms of the Attribution 2.0 Creative Commons License.

Case style shelving refers to any shelving systems that “uses a full panel, vertical component from floor to top with adjustable shelves or supports which engages at ends into these vertical panels.” Unlike cantilever style, Case-style will always have a canopy top and closed base shelf. Case style shelving can be single or double faced and constructed out of wood, metal or laminate on particle board. Built-in case style shelving is often referred to as casework or millwork. Metal case style shelving has become the least popular shelving type and is not as readily available (Siems & Demmers, n.d.).

Compact moveable shelving
Formerly installed only in closed-access collections, compact shelving is now common in public areas of libraries. High density moveable compact shelving eliminates the aisles between each shelving unit by utilizing one “moving” aisle. The shelving units are installed on tracks and one or more rows of units can be moved along the tracks using either an electrical or manual system. Compact shelving maximizes collection storage space and can double the storage capacity of a similar space with fixed aisles (Fraley & Anderson, 1990). Compact shelving can easily eliminate as many as five or six aisles (Siems & Demmers, n.d.). Drawbacks to moveable shelving are the maintenance required for the electrical or mechanical track system, limitations on patron browsing and difficulty repurposing the space due to the permanent floor track installations (Fraley & Anderson, 1990).

Custom shelving
Custom shelving can be expensive and is less flexible if permanently installed. However, custom built shelving has the capacity to act as a unique design element for creating an appealing space.

## Shelving Safety

Library building planners must consider the floor load. The dead load is the weight of the building itself; elements s
 Custom Shelving with integrated lighting, Minneapolis Central Library "Teen Central"; Obtained from flickr.com under the terms of the Attribution 2.0 Creative Commons License.
uch as steel, concrete and wood that make up the building. The live load is the weight of items or people that move or can be moved. Books and shelves, along with people, equipment, furniture, supplies and fixtures make up the live load. “Paper weighs 58 pounds per cubic foot and a normal double-faced bookstack, 3 feet long and 20 inches deep…and 7 shelves high, weighs about 2,320 pounds fully loaded” (Freifeld & Masyr, 1991). The weight drops to 1,972 pounds at 85% capacity. Floor load is especially important to consider when installing high density compact mobile shelving. Since this equipment can accommodate nearly double the volume of conventional shelving, the floor must in turn be able to hold twice the load (Freifeld & Masyr, 1991). Specifically, the floor must be able to handle at least 300 pounds per square foot, live load, before installing compact moveable shelving (Fraley & Anderson, 1990). One must also consider the floor load when developing a special library in a space not originally designed as a library space. Bolstering the building’s superstructure will allow the building to support additional weight (Freifeld & Masyr, 1991).

Seismic
Earthquakes can cause shelving to collapse or pitch their loads. Tall shelving is the most vulnerable to tipping over. For libraries in areas susceptible to earthquakes, structural engineers should be consulted for proper selection and installation of shelving (Wellheiser & Scott, 2002). Shelving installation in California must comply with state building regulations. Resources are available at The Division of the State Architect, the building standards commission, or in the published work, Manual of Recommended Practice, Seismic Safety Standards for Library Shelving by John A. Shelton (Siems & Demmers, n.d.). Even if your library is not located in an area prone to earthquakes, vibrations from construction, subways or air traffic can affect library collections.
There are measures one can take to keep materials on shelves and keep shelves upright:
• Install shelf lips or tilt shelves back to prevent material from falling off shelves
• Avoid free standing shelving units by bolting shelving to the floor, ceiling, wall or other units. Shelving bolted to the walls needs to be attached to the studs, not drywall.
• Metal shelves with welded frames and solid back and end panels are stronger than units with only bolted corners. In the absence of back or end panels, cross bracing on the back of the shelving adds extra support.
• Consider using compact mobile shelving when possible. They have added support due to their installation on the floor tracking and the closely connected units prevent materials from falling off shelves (Wellheiser & Scott, 2002).
Fire
Fire disaster planning tips for shelving:
• Shelve materials a short distance back from the edge to prevent the vertical spread of fire between shelves
• Do not shelve books too tightly: In the case of flooding, water will not cause the books to swell to the point that they burst from the shelves
• Do not store materials directly on the floor.
• Do not use the stacks as a storage place for empty boxes or supplies
• Compact mobile shelving can present a risk. Due to the high density of materials in one area, it can prevent an excessive fire load situation which can lead to collapse. There is also concern that dense storage areas can delay fire detection as a smoldering fire is concealed. Recommendations include automatic sprinkler systems for compact storage units and leaving a small gap between units (Wellheiser & Scott, 2002).

Libris Design
Libris Design article on Shelving
//Library Journal// list of Library Furniture resources (including shelving designers, suppliers & installation)

Some Library Shelving Suppliers:
Agati, Inc.
DEMCO, Inc.
Gaylord Bros.
Library Interiors, Inc.
The Worden Co.

## References

Bryan, Cheryl. (2007). Managing facilities for results: Optimizing space for services. American Library Association: Chicago.

Fraley, R.A. & Anderson, C.L. (1990). Library space planning. Neal-Schuman Publishers, Inc: New York.

Freifeld, R & Masyr, C. (1991). Space planning in the special library. Special Libraries Association, Washington D.C.

Klasing, K.P. (1991). Designing and renovating school library media centers. American Library Association, Chicago.

Library Administration & Management Association. (2001). Building blocks for planning functional library space. Scarecrow Press: Lanham, MD.
Ryan, R. (2005). Shelving systems for libraries. SCONUL Focus, (35), 51-52. Retrieved from Library, Information Science & Technology Abstracts database.

Siems, E. & Demmers, L. (n.d.) Library stacks and shelving. Retrieved from http://librisdesign.org

Wellheiser, J. & Scott, J. (2002). An ounce of prevention: Integrated disaster planning for archives, libraries, and record centers (2nd ed.). Scarecrow Press: Lanham, MD.