Tag Archives: Douglas Fir

Pressure Treated Douglas Fir

Pressure Treated Douglas-Fir

Reader ERIC in SANTA CRUZ writes:

“Hello, I am researching pressure treated pole and post treatments. I am looking at UC-4b treatment for long term. I need real life experience with Douglas fir using CCA-C . The other consideration is Douglas Fir using ACZA.”

Mike the Pole Barn Guru says:

Early in my post frame building career, I worked for Lucas Plywood and Lumber in Salem, Oregon. Owner Virgil Lucas would (about once a month) have our lumber yard crew gather up all dimensional lumber beginning to have a ‘sun tan’ (turned grey from being outdoors in weather) and send it off to be CCA pressure treated. His thought was this would hide discolorations. Well, hiding off color was correct, however much of this lumber was Douglas-fir and ended up basically being painted green from chemical preservatives, but actually not being anything close to adequately treated.

Today most CCA is composed of a mixture of oxides of chromium, copper and arsenic. Each component has a specific function — copper as a fungicide, arsenic as an insecticide, and chromium as a bonding agent, which “fixes” everything to wood. CCA treating mixture is supplied as a liquid concentrate, is diluted with water to appropriate level and then injected into wood under high pressure in large steel treating cylinders. After wood has absorbed all of the treating solution it can absorb, pressure is removed and a short vacuum is applied to pull off excess liquid. This wood is then air- or kiln dried before being shipped to lumber yards.

Once inside wood’s cellular structure, CCA treating solution undergoes a complex series of chemical reactions with major wood components — cellulose, hemicellulose and lignin. These reactions result in a bonding of CCA ingredients to wood fibers, rendering these chemicals insoluble and resistant to water-leaching. 

In order to accept CCA preservative solution, green lumber is usually dried to a moisture content of 25% or less. This is accomplished by either kiln drying or air seasoning. During treatment, wood fiber becomes completely saturated with preservative solution, being mostly water. After the treatment process is complete wood is still virtually 100% water saturated.

Highest grades of treated wood are kiln dried after treatment to bring moisture content down to 19% or less. However, it is more typical to allow this wood to air dry to reach equilibrium moisture content. In some cases treated wood will reach lumber yards while still very wet.

Many types of softwood can be pressure treated with CCA preservative; however, the most commonly treated species is Southern Yellow Pine. In the West, Hemlock, Hem-fir, Ponderosa Pine, Jack Pine and Red Pine are also subject to CCA treatment. Some species, such as Douglas fir, have difficulty accepting waterborne treatments; these are said to be refractory. To promote penetration of preservatives, these woods are sometimes mechanically incised before treatment. Treated lumber will then have characteristic rows of incising marks. (Read more about incising here: https://www.hansenpolebuildings.com/2014/08/incising/).

American Wood Protection Association (AWPA) set standards for United States pressure-treated wood. These standards set requirements for preservative level in wood, depth of penetration, treatable species and other important treating parameters. Adherence to standard is checked by way of third-party inspection at treating plants. Those treaters who consistently meet AWPA standards are allowed to display AWPA and third party inspection agency marks on their lumber.

Treated lumber will also often bear a grade stamp and a mark designating level of CCA treatment. Grade stamps are similar to those for untreated lumber. CCA level is listed as a retention number, which represents pounds per cubic foot (pcf) of preservative in wood. For above-ground applications specified retention of CCA is 0.25 pcf, for ground contact uses it is 0.40 pcf, and for structural in ground use it is 0.60 pcf.

Fixation and leaching characteristics of chromated copper arsenate (CCA)-treated Douglas-fir sapwood and heartwood have been evaluated using expressate method and American Wood Protection Association (AWPA) El 1-97 leaching procedure. CCA fixation, monitored by hexavalent chromium reduction, was much faster in heartwood than in sapwood; copper and arsenic fixation in heartwood appeared to be incomplete, regardless of duration of fixation time. Poor fixation of copper and arsenic in heartwood was confirmed using leaching tests. Based on results, it has been concluded CCA is not an appropriate preservative for Douglas-fir heartwood because of its poor fixation quality.

Due to this, ACZA remains the first choice for pressure treating Douglas-fir. You may want to consider the use of Hem-fir treated to UC-4B standards with CCA, MCQ or MCA due to pricing and availability issues.

Would Sycamore Lumber be a Good Choice for Building a Pole Building?

Would Sycamore Lumber be a Good Choice for Building a Pole Building?

Reader TRACY in SMITHFIELD writes:

“I’ve been given a lot of sycamore logs fairly newly cut. Would that be a good choice to use for building a pole building? I have read several different things and some say no because it has a spiral grain and one said yes but only if it is still green. So I’m getting a lot of yes and no and I’m not sure which to go with. Any info you could give me about using sycamore to build my pole building or the type of wood that would be a better choice would be greatly appreciated. thank you.” 

Mike the Pole Barn Guru responds:
American sycamore is something of a sleeper as far as native hardwoods go. For years it was used as a secondary wood—for drawer sides, web frames, etc.—if it was processed into furniture-grade lumber at all. Often, sycamore wood has served more humbly for items not requiring high-grade stock, such as pallets. One reason is plainsawn sycamore doesn’t dry well, twisting and bowing significantly unless preventative measures are taken. Sycamore has little to no rot resistance and is very susceptible to insect attack. Sycamore is not a particularly strong wood to begin with, and once it begins to decay it can become brittle and weak.

Sycamore wood is used for many products. It’s solid, very durable and difficult to split.

People and companies use it for different types of furniture, including bed frames, headboards, dressers, and even countertops in homes. Sycamore wood can also be used for making hardwood floors.

Solid and stable, a sycamore wood cutting board among most popular choices among butchers and cooks for cutting meats and other food items. Sycamore boards are not as brittle and easy to break apart than cutting boards made of oak or maple. They are also common in kitchens as butcher blocks.

If you love woodworking or even whittling, sycamore wood is a good option for DIY projects and hobbies. It retains a hard-wearing edge great in quality, perfect for carved items. It also alleviates any concerns about durability.

You will be best served to sell your sycamore logs, rather than trying to build with lumber milled from them.

For structural framing members, best species are Douglas Fir, Canadian SPF (Spruce-Pine-Fir), Hem-Fir and Southern Pine. Whomever you order your fully engineered post frame building package from will have proper lumber specified by their engineer.

Protecting Posts from Rot

Protecting Posts From Rot

Based upon a Journal of Light Construction article by Grant Kirker, research forest products technologist at USDA’s Forest Products Laboratory in Madison, WI

Posts rot when decay fungi find wood they can digest. Insects such as subterranean termites can also cause posts to fail, but they aren’t common in cold climates, whereas fungi are widespread. Posts often rot at ground level and break off simply because this is where conditions are most conducive for decay to occur, as well as being where highest physical stress occurs. Here, fungi find those three basic things they need to grow and survive: moisture (from soil), oxygen (from air), and food (post itself).

While some wood species—such as eastern white cedar and black locust—are naturally resistant to decay fungi, their performance is highly dependent on extractive content in heartwood, and can be variable. Preservative treatment is a more controlled process resulting in more predictable performance, especially in soil contact. Wood preservatives have historically been formulated to be broad spectrum so they protect from a wide range of organisms. Most waterborne preservative systems commonly used today employ a metallic component (usually copper) combined with co-biocides to improve resistance to copper-tolerant fungi, molds, and bacteria. Our studies have found yellow-pine posts treated with several industrial wood preservatives (including CCA, ACA, pentachlorophenol, and creosote) have remained highly durable even after 50 years of field exposure in a harsh environment.

U.S. Forest Service Harrison Experimental Forest test plot in Saucier, Miss.—classified as a severe decay hazard according to AWPA’s Fungal Decay Hazard Map—is filled with longleaf-pine posts.

U.S. Forest Service A post is assessed by giving it a lateral pull of 50 pounds. If a post breaks at the ground line, it fails; if it doesn’t break, it passes. Tests have been conducted on these posts using this protocol since they were installed in 1964.

In order for a preservative to be effective, wood must be treated to proper retention level and penetration. If wood is treated only on the surface, any cracks or splits open up the treatment envelope and expose untreated wood, and can be readily eaten by fungi and insects. Some wood species (southern yellow pine, for example) are easy to treat and take up preservatives readily, while others (such as Douglas fir and lodge-pole pine) are more difficult to treat due to their wood cell orientation or heartwood presence. These species are often referred to as “refractory” and may require additional preparation (incising, steaming, and so on) to open up wood so it better accepts treatments.

When choosing wood for posts, check the end tag to confirm lumber is pressure-treated in accordance with either, American Wood Protection Association (AWPA), or International Code Commission (ICC). On the label, look for the product’s designated Use Category, or UC. The AWPA’s Use Category system specifies target retention levels for different preservative types to meet specific applications; UC 4B lumber (with a 0.60 pcf retention level for CCA, ACZA, and ACQ or 0.23 pcf for MCA) is required for harsh below-ground exposure in wet areas or regions with high decay hazard (like Southeast or Hawaii).

It’s not necessary to special-order heavy-duty marine-grade PT lumber. Marine pilings are typically treated to retention levels as high as 2.5 pcf CCA (chromated copper arsenate – generally no longer available for residential use) to ward off marine animals such as limnoria, teredo, and phloads, since some of these pests have been found to be copper tolerant. But for soil exposure, higher loadings aren’t necessary and just increase product cost.

U.S. Forest Service In addition to long-term industrial wood preservatives field testing, Forest Product Laboratory conducts research to develop new and improved treatment schedules for a variety of wood species. FPL’s state-of-the-art wood-treating pilot plant, constructed in 2010, offers five different preservative treatment retorts and can accommodate samples up to 12 feet long.

If you have to cut a PT post, be sure to dress any field cuts with a copper-naphthenate preservative containing at least 1% elemental copper. Examples include Copper-Green’s Wood Preservative (coppergreen.com), Tenino copper naphthenate (coppercare.com), and Woodlife Coppercoat (rustoleum.com). Cutting, drilling, or notching PT lumber exposes wood inner faces possibly not treated to the same retention as outer surfaces.

Some installers report wrapping post base with sheet copper or galvanized steel prolongs post life. While post wraps and barriers seem to offer some increased longevity, any gaps, holes, or voids behind the barrier or wrap will compromise the barrier and make it less useful. Coating post base with asphalt roofing cement, driveway sealer, tar, or a bituminous self-adhesive flashing tape are fairly common practices. In concept, these practices would seem to block some moisture transfer into wood, but there isn’t any research to suggest it increases longevity.

Finally, setting posts in concrete offers several advantages. First off, it reduces lateral post movement once it sets, making installation balance much easier. For square posts in foundations, it eliminates some shifting and settling. A recent European study evaluating concrete vs. gravel vs. dirt fill found concrete fill was a best option in regards to longevity and durability, but again, proper pressure treatment is key to long-term field performance. If fully encasing posts in concrete, be sure to bring concrete sleeve above grade and slope top surface away from post to shed water, as recommended in most local building codes.