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Date Posted: 19-Jul-2006

Go UP Not OUT!

 Next time you need more space, think "up". Article from Material Handling Magazine written by Dave Luton.

The average warehouse has volumes of wasted space floating high above the floor. So, if you need more room, you may want to think about adding a mezzanine. Go into any warehouse and you will see potential for better use of the available cube.

Mezzanines, or work platforms, are one of those basics of warehousing we tend to take for granted, but they have their place. When properly used, they can increase warehouse space and capacity. Work platforms, or "equipment mezzanines' (to differentiate them from structural concrete mezzanines, which form part of the building), are a free-standing second-storey addition to an existing structure. They do not require any attachment to the existing building except for the weight supported by the floor for structural support.

Major Canadian warehousing centres today will have ceiling heights of at least 28ft clear. This clear height (just) permits the use of three-storey mezzanines instead of the two-storey structures we traditionally think of. As the basic design of warehouses gets higher, work platform applications will grow in the future. One of the chief advantages in these structures is their flexibility in design, which permits a wide variety of uses under most building conditions. In addition to their versatility, their cost is often only 66 percent of the cost of comparable new building construction.

Most of these structures are subject to a wide variety of government rules and regulations. These include municipal and other relevant building code regularions. Most municipalities regulate work platform construction and usually require a building permit.

Work Platforms Usually Require:

Proper engineering, structural and fire protection design by a certified engineer for the platform, as well as the foundation; Special design for areas of higher earthquake risk, such as Canada's West Coast or Cornwall, Ontario; Proper fire protection, such as sprinklers beneath the deck and proper fire rated materials; Proper lighting; Zoning clearance for additional parking and other related needs; and *A maximum permitted floor coverage area of the available ground floor area. This is done to avoid classification as a second storey, which comes under different rules. Depending on the jurisdiction, it is usually about 40 percent of the total square floor area of the building.

Other Things to Consider:

1. Depreciation rating. Work platforms are favourably treated, and if they are properly classified they are charged at 20 percent as equipment. Building additions, by contrast, are charged at five percent.
2. Clear building height. Usually I like at least 16ft clear to provide eight feet clear on the bottom. This allows for a deck height of around nine to 10ft. Note a deck height above 12ft will require a landing for stairs.
3. Decking. The key issue is whether a smooth floor is needed (say, for picking with a cart) or whether an open floor is acceptable. Smooth floors are commonly of roof deck and plywood construction, but they can be upgraded with composite tongue and groove floor options for increased durability with products like resinDEK. Steel flooring options include roof deck and diamond plate or those treated with a plasma stream deposition process antiskid steel flooring, such as SlipNOT. Open floors are commonly of open steel plank or weldedsteel grating (checker plate or welded bar and rod) construction.
4. Design load. The design load of a mezzanine will commonly specify the capacity of the mezzanine in pounds per square foot (psf). The load rating is also referred to as the uniform live load and is what the structure can safely carry when fully loaded. Most commonly, work platforms are designed for 100 to 150 (psf) rating, but the codes specify minimum needs.
5. Span or column layout. The use of the area under the mezzanine, cost and floor loading considerations are commonly the chief determinants of the mezzanine design. The supports for the mezzanine can be shelving, racking or structural steel columns. Long spans reduce the number of obstructions but increase the cost of materials and often require concrete footings. Normally, in considering the span needs, one dimension is critical and the loads can be reduced by placing supports closer together in the non critical dimension. For a smaller work platform placed next to the building walls, use of a rack-supported mezzanine may permit it to be on a regular floor without the need for additional footings or slab thickening.
6. Accessories. There are a wide number of mezzanine accessories, including: Safety gates for pallet handling; Landings for staircases that run parallel to the mezzanine; Reinforced pallet drops (eg Diamond Plate) to prevent wear; Kick plates and security fencing to prevent product falling off the mezzanine; Handrails around the perimeter of mezzanine for safety. Lately many building departments have been insisting on picket fence-type handrail design around the perimeter of a mezzanine; and Barrier rails, which can also be used for perimeter safety.
7. Installation considerations. Is the site free and clear? What will the cost of labour be? Will you have to install during off-hours, thus increasing the cost? Who will supply lifting equipment? Is there power and lighting at the site? The potential uses of work platforms are almost endless, ranging from overhead office space to office records storage to spare parts storage. I have yet to see a warehouse in which a properly designed mezzanine fails to have an application.

Next time you need space, think "up' instead of "offsite': One factor many companies fail to consider when they look at this option is the savings in additional land often needed for new building construction.

Dave Luton is a consultant based in the greater Toronto area, h4MhD March 2006 65.