The construction of piers may take several forms, wooden driven piles, metal framing, masonry and/or rubble construction. Metal constructed piers are generally found in commercial applications, and rarely found in residential usage. The cost of installation of the metal, coupled with the cost of maintenance, especially in salt water, is extremely high. A metal pier is much stronger than the wooden pier. It is well suited for many commercial activities because of its load-bearing capacities. However, these requirements are not typically found in residential applications.
Masonry and rubble construction is more expensive than that of the wood-driven piers. However, construction does provide low maintenance costs. Masonry and rubble construction of piers is rarely found because of the problems associated with using the pier for boating. As with the metal piers, masonry and rubble are rarely found in residential applications.
Once the pilings have been driven, girders or crossbeams are attached to the pilings with galvanized bolts. The pilings should be notched deep enough to provide a shelf for the girder or crossbeam to bear upon. If the pilings are not notched, steel straps are often used to assist in securing the girders or crossbeams to the piling.
Once the girders or crossbeams have been properly secured and aligned, stringers or joists are then installed on the girder system to form a walkway. The size and thickness of the joist is determined utilizing the same procedures as used in determining load-bearing capacities for floor joists on the interior of a building. Like the girders or cross beams, the joists are attached to the piers with galvanized bolts or lag screws.
Once the stringers or joists are in position, decking can be applied. Generally, the decking is a 2 x 6 or 2 x 8 dimensional lumber that is secured to the stringers or joists. A minimum of 1/4-inch spacing is left between the decking members to allow water to drain off of the pier.
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Wooden piers are generally constructed with pressure treated marine grade material. This material is clearly stamped and identified for water contact. In the past, wooden components were treated with a creosote material, which is essentially an oil-based tar residue that is saturated in the material. This material, over time, may deteriorate and require replacement.
The Army Corps of Engineers, which controls the waterways in the United States, have for the past several years resisted permitting the use of creosote material. The pressure-treated material releases pollutants into the water, is more available to the general public, and has a much longer life expectancy for these usages. Standard grade lumber should never be used for pier applications. Standard material deteriorates very rapidly. Due to the need of using a treated material, such as pressure-treated pilings, girders, stringers and decking, the cost of installation of a pier is rather expensive. You must also consider the cost of notching the pilings, setting the girders, and the cost of the girders themselves. Typically, two girders are required per pair of piles.
The life expectancy of a properly installed pressure-treated pier is 20-30 years with annual maintenance. The normal life expectancy of a creosote structure is approximately 12-18 years.
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Water and Electrical Supply
Many piers may also have electrical and water supply. It is important to remember that the wiring be sunlight resistant and/or UF cable. All of the electrical junction boxes, light fixtures, etc. should be in waterproof-approved fixtures, and the entire system should be protected with Ground Fault Circuit Interrupter (GFCI) devices. Extreme caution should be used in evaluating and checking the electrical system around any wet location, especially in a pier or waterfront. The hose bibs located at the pier area should be properly secured and should be the approved type that would allow proper draining.
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