Treated pilings are large round timbers that have a slight natural taper from the butt end to the tip. They are typically driven into the ground tip-first and used to support a larger structure, such as home that is raised above the flood line or a dock, pier or other marine structure. They can also be used as bulkeading material near water lines or slopes to hold back soil, or as deck supports, utility poles, or structural components in buildings like pole barns.
They are treated with one of several chemical formulas, such as chromated copper arsenate, which prevents damage from water, fungal growth, insect infestation and ultraviolet light. This allows treated pilings to last for decades in harsh environments, where frequent exposure to fresh water or salt water is common, or even in permanent immersion. The treatment process involves soaking the timbers in the chemical preservative, using cycles of high pressure and vacuum within a sealed chamber to drive the chemicals deep within the wood and remove excess chemicals. The process makes treated pilings much more resilient than natural wood, while still keeping the overall costs lower than alternative materials, like composites or steel.
Treated pilings are strong, durable, economical, and are often the best choice in areas with frequent moisture exposure. Here are a few factors to consider when purchasing treated pilings:
#1 The Application
Where the treated pilings will be used determines what type of chemical preservative is necessary and what the concentration should be. When used in above-ground settings, with only occasional exposure to moisture, fungal growth or insect activity, only minimal protection is necessary. If the treated pilings will be used below-ground or immersed in water, more protection will be necessary, such as increased amounts of preservative or alternative formulations.
#2 What Type of Preservative is Used
Most treated pilings are impregnated with chromated copper arsenate, which provides good protection against saltwater, freshwater, fungal growth, insect infestation and ultraviolet light, depending on the treatment level. According on the application and the environment it is to be used in, other chemical formulations can be used as well, including creosote for utility poles, borate, for better protection against insects, or alternative copper-based chemicals, such as alkaline copper quaternary or copper azole, which provide increased protection against fungal growth and microorganisms. In most cases, chromated copper arsenate is the best choice, but specific applications may require alternative treatments, which may be more expensive, or difficult to obtain, depending on the supplier.
#3 The Concentration of Preservative
When using treated pilings in above-ground applications, for main support beams or for vigas in a roof system, minimal chromated copper arsenate levels of between 0.15 and 0.25 pounds per cubic foot can be used. For applications like utility poles or deck supports, where there is permanent ground contact, treatment levels of between 0.35 and .040 PCF are recommended. When used as foundation piers or for fresh water immersion applications, the CCA concentration should be 0.60 PCF, for added resistance to damage, and for saltwater immersion, the concentration should be 2.5 PCF. Often, custom treatment levels are available on request.
#4 Size Requirements
Treated Pilings are available in many dimensions, with standard butt-end diameters from 8 inches to 12 inches, and standard lengths from 8 feet to over 50 feet. Typically, there are custom sizes available on request. Smaller structures can often use smaller-diameter pilings, which are less expensive per foot of length, and larger structures can be designed with shorter spans between poles to use smaller-diameter pilings. Large diameter pilings are available for large, heavy structures, or structures with greater spans between pilings. For exceptionally tall foundation pilings, greater diameter will also be required, and the amount of the piling buried will also have to be considered. Check with the supplier to be certain they have the required sizes for the project on hand.
#5 Quantity Required
The number of treated pilings required for a project depends on the design of the building, the load requirements and the spacing of the pilings. Large, heavy structures will require more pilings spaced at a closer interval, or pilings with larger diameters to compensate for the increased load over a greater span. Smaller structures may require fewer pilings. Once the quantity of pilings is determined, it is a good idea to check with the supplier to ensure the required number of pilings are available or can be ordered.
#6 Shipping Options
Transporting treated pilings, especially longer lengths, can be difficult. Check with your supplier to learn about available shipping or delivery options, as well as the costs and the amount of lead time that is required before the order can be shipped. To make sure that the treated pilings are available when needed, it is best to contact the supplier early to place the order and make arrangements for shipping.
#7 Choice of Contractors
When considering a project that uses treated pilings, choose a contractor that has experience working with them. The contractor must have the tools required to install the pilings, such as pile drivers, saws, drills and other equipment, and the knowledge necessary to design and build a structure that is safe, with the appropriate-sized pilings for the required loads and the proper building techniques. Working with large timbers is very different from traditional framing techniques, and requires different set of skills.
Treated pilings are a great choice for many types of structures, including docks, piers, bulkheads and elevated homes. They offer many advantages over other type of timbers, such as square timbers. This includes less exposed heartwood, reduced twisting or warping, and lower costs, especially for larger or longer timbers. With the proper chemical treatments, they can last for decades in the harshest conditions, including constant immersion in fresh or salt water, and they are less expensive than alternative materials such as composite poles or steel components. They are available in multiple diameters and lengths to fit the application perfectly.