The life span of your treated posts posts matters. Before spending thousands, or tens of thousands, of dollars on a fence it is nice to have a better idea of how long you can expect your investment to last.

So, to answer the question: How long will my treated posts last?

According to the Southern Pine Council you can expect properly treated posts to last many decades. They site a study by USDA Forest Service’s Forest Products Laboratory saying:

Test stakes of treated wood have been buried in the ground at various locations, stretching from the Mississippi Delta to the Canadian border. Data analysis indicates that CCA-treated Southern Pine stakes in place since 1938 have shown no failures at chemical retention levels of 0.29 pounds of preservative per cubic foot of wood, or higher.

Most treated posts are treated to a retention of .40 but you should always ask - just to be safe.

Here’s a great pdf from the USDA with expected life spans for various species of treated posts including a comparison of the life spans of treated and untreated posts (see page two).

If you want a guarantee that your posts will last you can get treated posts coated at the ground line from American Pole and Timber. I mentioned these posts before in How to Build a Fence that Lasts because I have seen them up close and they are tough. They claim that posts coated at the ground line with their poly coating will last fifty years.  In reality, the posts should last 150 years because the ground line is the source of infestations and the place where decay begins.  If that is protected, you don’t have much else to worry about.

The bottom is that the life span of properly treated posts should be at least 20 years and can be easily extended to 50+ when installed and used in normal conditions (not in water or along the coast, for instance) .  If you choose the right materials, your grandchildren won’t even have to deal with building another fence.

I am regularly asked about pole prices - everything from prices per size to freight costs and installation, etc. The object of this video and chart is to briefly explain the basic pole prices relative to length, the most commonly discussed characteristic of the pole.

Poles come in numerous sizes, species, grades, and treatment levels. Each of those factors affects price. The biggest factor affecting the delivered price of a pole (treated or untreated) is size - mostly length - and that can be broken into two main reasons.

1. Supply: Trees take a long time to grow and BIG trees are getting scarce.
2. Freight: Permits and special equipment are probably required for long lengths.

In fact, if you order an 80′ long pole today it is likely the tree you will receive is still in the forest today. Crazy, huh?

The chart does not appear clearly in the video. Here it is (below) so you can get a better look.

Don’t use this chart to bid your next project or anything. I simply wanted to make the point that around the 50′ length mark, the pole prices curve turns sharply north. Also notice that the incremental pole prices on the left get larger as well. Yes, it is certainly possible that you might pay $5,000 (delivered) for a 90′ pole. Don’t even ask about poles beyond 100′.

You should always design based on the needs of the structure (as opposed to what materials are cheapest) but “value engineering” is always important to keep budgets in check and projects affordable. With that, if you are building a structure that requires poles longer than about 50 feet, you might consider brainstorming ideas to design the structure so it can use shorter, less expensive, poles.

Basic Take Away about Pole Prices (in a rhyme): Under 20 feet, poles are cheap, beyond fifty, prices are ‘iffy.

According to a study from the Western Wood Preservers Institute the expected life of wood utility poles can be conservatively estimated at 75 years or more when they are properly inspected and maintained. Interestingly, most utility companies estimate the serviceable life span of a pole to be only 35+/- years.

Wood Utility Pole Treatments

Utility poles are usually treated with either pentachlorophenol, chromated copper arsenate, copper napthenate, or creosote. Whichever preservative treatment is used, the main goal of the treatment is to extend the life of the pole by rendering the wood useless as a food source for termites and other wood boring pests and to reduce the effects of decay caused by rot and decay. All of the treatments listed above provide excellent life spans for poles. They are usually chosen based on factors including climate where the poles will be installed, environmental impacts of the chemicals used, concerns around how the poles will be handled, and even individuals’ preferences.

The Biggest Problems for Wood Utility Poles

Most decay of wood utility poles happens at the ground line where the poles are often in contact with moisture which causes rot and decay. Wood utility poles do not have many other natural enemies other than the occasional fire, woodpecker, or car wreck. Wood utility poles are quite resilient and can withstand many natural conditions including high winds, acidic soils, and salty air - conditions steel and concrete poles may not withstand as well.

Increasing the Life of Wood Utility Poles

Properly treated wood utility poles are nearly guaranteed to last about 35 years without any inspections, maintenance, or preventative measures. However, the life span of utility poles can be drastically increased (easily doubled) through a regimen of periodic inspections and maintenance such as pole wrapping, which requires digging around the pole and literally wrapping the pole with a protective barrier. An excellent preventative measure is to coat the pole with the polymer wood coating from American Pole and Timber. The polymer coating must be applied before the pole is installed but provides a protective barrier that will prevent the need for labor intensive pole-wrapping in the future.

The study I mentioned at the beginning of this report actually suggests that utility poles can last more than 135 years (up to 260 years - yes, two, six, zero) but that over time other “degradation mechanisms” take their tolls. Typical maintenance programs are not geared towards correcting those issues which include pole top decay, pole splitting, decay at connections, and excessive weathering so the reasonable estimate of a wood utility pole should probably remain in the neighborhood of 75 years.

Applying Your New Knowledge of Wood Pole Life Spans

There is a great chance you are not in the utility business and just want to know how long your barn poles will last.  While there are no hard numbers on that - at least not that I have found YET - this study reveals that the life is probably longer than you might have even hoped.  Barn poles, fence posts, and small electric poles are treated with the same chemicals as utility poles and usually to the same retention levels using the same methods.  Though utility poles are held to higher standings of structural grading and specifications than your average barn pole you can probably expect the life spans to be similar. Again, the extended life span requires some periodic checks and maintenance.

If you are using treated poles or pilings around a marine environment, the rules are a little different since the surroundings are wetter and generally more dynamic and harsh (waves, changing tides, different organisms, constant contact with water).  Properly treated poles or pilings for freshwater applications can probably be made to last 30 years with proper preventative measures and maintenance.

Here’s some solid logic.  Think of all those old barns and fences that were built by your grandfather’s grandfather practically forever ago. While “they don’t make ‘em like they used to”, the treatments have improved.  You can expect your treated wood poles to last a lifetime.

I made a sketchcast about how to build a wood bulkhead and I wrote about how to build a wood retaining wall but I might have assumed too much about how much you know about the bulkhead materials I listed. They are slightly off the beaten path from “regular” building materials you’d find at your local hardware store so here is a breakdown of basic wood bulkhead materials.

Wood Bulkhead Materials List

Building a wood bulkhead is similar to building a privacy fence. You have posts (pilings), rails (wales), and pickets (sheets or sheeting). A bulkhead typically has great horizontal force applied against it, though, so it has more structural requirements than a fence. In order of front to back (water side to ground side) the parts of a wood bulkhead are:

• Pilings (can be round or square)
• Wales
• Center Match (sometimes call “sloppy tongue & groove”)
• Filter Cloth
• Tie Rods
• Deadmen
• Top Cap
• All the required Hardware (nails, screws, spikes, nuts, washers)

Attention: First, the materials required for YOUR wood bulkhead might be different from those I am showing below so please have your bulkhead designed and specified by a professional builder and/or designer. Also, be sure to use the proper materials for the best longevity. Using cheap materials to save money NOW is only wasting money in the long run. Use properly treated wood, galvanized or stainless hardware, and make sure the bulkhead is installed properly.

Treated Pilings

You can use round or square pilings. It is totally up to you. You might want to match your neighbors’ bulkheads or you might be concerned about costs (round pilings cost less). Either way, use properly treated wood - 2.5 pcf in saltwater and a minimum of .60 pcf in freshwater. For brackish (mixed fresh and salt) water, go with 2.5 pcf.

Wales

Wales are the horizontal boards (like the rails on a fence). Most wood bulkheads have two but some will have three or more. Wales are connected to the land-side of the pilings and will have the center match sheets nailed to them. A very common size used for wales is 3×8. You should use the longest lengths possible to minimize joints, which can become weak spots. You should be able to find 3×8-20’s from most marine construction suppliers. Many other sizes are commonly use depending upon the sizes of the bulkhead and the forces applied to it. I have seen wood bulkheads with 8×8 wales.

Center Match

Center match are sometimes called “sloppy tongue & groove” because the joint is a little loose to allow for swelling in the water so the edges will not break with regular expansion and contraction when the boards alternates between wet and dry.

Center match is usually nominal 2×10 with actual dimensions of 1.5″ x 8.9″. That is, because of the groove each board only spans 8.9 inches - very important to factor into your bulkhead materials list. I have heard of numerous people making an extra trip to the dealer (or paying for another delivery) because they were 5 pieces short of center match.

Filter Cloth

Filter cloth is kind of like a very thick felt. The purpose of filter cloth is to stop silt and dirt from seeping through the spaces between the center match while allowing water to drain and relieve hydrostatic pressure from the bulkhead after a rain - it helps maintain a cleaner appearance and keeps soil behind the bulkhead where it should be. While some people use plastic for this purpose, I truly believe a quality geotextile filter cloth is better because it allows the water to drain. Filter cloth is cheap - use it.

Tie Rods

Tie rods support the structure from behind to keep it from falling forward (into the water). Tie rods will be connected to the pilings on one end (via hold drilled from the front to back of each piling) and to deadmen on the other end. They are simply long rods with about 12″ of threads on each end for a nut.

Builders usually use tie rods that are about 3 times as long as the exposed height of the bulkhead being built. For example, a 4′ tall wall will commonly use 12′ long tie rods. The come in diameters including 1/2″, 5/8″, 3/4″, and larger. Some people use cables instead of tie rods but tie rods are stronger and they can easily be tightened if needed.

Deadmen

I have no idea why deadmen are called deadmen but I can make up some good stories about medieval times and using what you have to protect the castle if you want.

Dead men are treated posts - round or square and often cutoffs - used to “tie back” the bulkhead and support it from behind. Like the rest of the materials, the size of the deadmen used should be based upon the overall height of the wall and the load it bares.

Top Cap

Most top caps are made using a regular S4S 2×12. While they are not required, top caps will provide a little more structural integrity while giving the wall a more finished appearance from above.

Hardware

Use galvanized or stainless steel hardware when building on or near water. Screws are better than nails but more time-consuming. Generally, you will need the following hardware for your bulkhead:

• Tie Rods with 2 nuts and 2 washers for each
• Spikes (60 penny nails) to attach the wales to the pilings
• 16 penny nails (or larger) to attach the center match to the wales and the top cap to the wales
• Staples to attach the filter cloth to the center match

The materials list for a wood bulkhead is pretty simple and short. The bulkhead materials listed above will work for most wood bulkheads or retaining walls built around residential locations. If you need a reliable source for wood bulkhead materials, call the people at Building Products Plus in Houston, TX who let me take the pictures above in their yard. They ship nationwide so you can call them from anywhere.

Here’s a simple sketchcast from WoodScience (became Lumber Talk) on how to build a wood bulkhead.