Types of Wood for Backyard Projects
If you are planning a backyard project such as a screen, deck or gazebo, the type of wood you choose will impact how well and how long it stands up to the elements. In some ways, nature can be your worst enemy: from the moment your project is completed and takes its place in the garden, it becomes prey to wood-boring insects, mold, fungus, moisture and sunlight. Selecting wood suitable to your requirements will ensure many years of enjoyment.
In general, hardwoods are fine-grained, dense and heavy. They are less likely to splinter than other types of wood. This characteristic makes them ideal for handrails and garden furniture - both situations in which splintering is particularly undesirable. Hardwoods are also fairly decay resistant due to their natural resin and oil content. The natural oils of most hardwoods impart rich colour which can be enhanced with an application of wax, oils or lacquer.
Some commonly used hardwoods include oak, chestnut, teak, mahogany, maple and cherry. Although redwood and cedar are technically softwoods, they are often classified as hardwoods for construction purposes because of their notable decay resistance. Redwood and cedar can withstand the elements for decades, however they are relatively soft and more easily damaged. It is best to use these two species for decorative projects.
Two notes of caution regarding hardwoods: (1) use fine-toothed saws to prevent splits and chips and (2) because hardwood tends to be more expensive than softwood, the cost may impact the scope of a project.
Softwoods are typically from coniferous trees such as pine or fir. They tend to splinter more easily than hardwoods due to their open grain. As the name implies, softwoods are relatively soft but they are strong and suitable for many types of construction. In their natural state, softwoods tend to decay fairly quickly in the soil and need treatment if they are to last an adequate length of time.
Pressure treatment is one way to slow the rate of decay. Persistent chemical preservatives are applied to the timber in a pressure chamber. The chemicals are able to saturate the wood to a high degree resulting in timber that can withstand the elements for 20 years or more. An alternative method is to spray the timber with a preservative, however, it may not last as long as pressure treated products. The preservatives used in both methods often cause a slight bluish-green discolouration.
One of the most serious concerns about pressure treated timber is arsenic poisoning. Playgrounds and decks have traditionally been built with pressure treated timber putting children at particular risk. They play and crawl on these surfaces and often put their hands in their mouths. CBC news reported in November 1998 that arsenic continued to leach out of timber for several years and one study indicated a disturbing positive correlation between timber age and the rate of leaching.
At your local home renovation store, you are likely to find CCA pressure treated timber. CCA stands for the chemicals used in the preservative: copper, chromium and arsenic. According to Dr. Paul Cooper, a scientist at the University of New Brunswick, copper acts as a fungicide, arsenic protects against insects and chromium helps keep the other two chemicals contained in the wood.
Recently, Canadians have been able to purchase a product that has been available to Americans for years: ACQ (which stands for alkaline, copper and a complex chemical called quat). ACQ is considered a less toxic option and is slightly more expensive than CCA.
Nothing can replace the unique charm of rustic wood; the bends and twists of branches can create a rose arbour, a chair and other structures that seem to meld perfectly with the garden. Rustic timber refers to wood that has not been planed (sawn into planks). The shape is typically round and the poles can range in size from small branches to tree trunks. The bark may or may not be left intact.
Common products created with rustic timber are benches and chairs. The bark is often removed and the wood is pressure treated to increase longevity. If you are buying rustic timber from a home renovation store, it will most likely be pressure treated softwood.
Pressure treatment can only be applied to poles that have been stripped of bark. If you prefer the look of bark, sweet chestnut (Castanea sativa) is a good option. This species is very resistant to decay and does not require pressure treating. Oak is another good choice although the branches are not particularly straight.
If you have deciduous trees in your yard, careful pruning may allow you to gather enough branches to build the structure you have in mind. A major benefit of doing this is that the wood is free. Even if you do not have sweet chestnut or oak trees in your yard, other types of deciduous trees (e.g. maple, dogwood, beech etc) will provide rustic wood that can last for years with some preparation.
The most vulnerable part of any structure is the section that makes contact with the soil. Because soil retains moisture, it speeds up the deterioration process of the timber. Wood-boring insects will also find the supports and legs of furniture to be a tasty and easily accessible treat. To help preserve poles with their bark left on, you can treat the ends that will be in contact with the soil. Strip the bark from the section that will be buried and soak it in a penetrating preservative (available from home renovation stores) for 48 hours. Another option is to char the end in a fire. The best way to char timber is to place the end in red hot coals. Check the progress frequently and avoid flames.
As the name implies, rustic wood is meant to look natural and even a bit weathered. If you wish to add some sheen and boost the longevity of the above ground sections, you can apply wood penetrating oils or a few coats of lacquer. The latter will help to seal any cracks in the bark and reduce moisture and insect infestations.
The type of wood you choose will depend on the look you wish to achieve and the desired longevity of your project. Now the only limit to your woodworking is your imagination!