As a whole, untreated wood can be used outside. Proactive steps should be taken to make untreated wood a viable option for long lasting projects when used outdoors. Steps such as sealing, painting or using other bonding agents to increase the life of untreated wood.
Varnish is great option to treat untreated wood for outdoor use because it's relatively cheap and provides superior protection for your wood. It can also last longer than some other sealants, which is something we all want. The only downside is that you'll lose the texture and feel of your wood because of the finish.
Redwood and Cedar. While pine is the best exterior softwood for the money, Redwood and Cedar are better exterior softwoods for stability. Redwood and Cedar are pinkish, with heart redwood being a darker pink than Western Red Cedar.
Generally, you can use non-pressure-treated wood outside for about 2-5 years if it is not maintained or protected from high humidity, heavy rain, or prolonged exposure to sunlight.
Whether it warps or discolors or both will be revealed in the next 2 or three days. What is going to happen is the wood grain will be "raised". All this means is the fibers that make up that particular section of wood that got wet will swell from re-hydrating.
But don't worry, framing material is made to withstand exposure to moisture. In fact, the glues used to manufacture OSB (Oriented Strand Board) are water-resistant. Even loose lumber not treated in any way will be fine; provided it has an opportunity to dry out before covering with drywall.
Untreated wood can last anywhere from a few months to several years, depending on different factors such as the type of wood, the climate, and the level of exposure to the elements. For example, cedar and redwood are naturally resistant to decay and can last up to 20 years or more.
Wood can Start to Rot in 1-6 months If:
Wood is untreated. The wooded area is sitting in water. Water and/or air space is hot & humid.
The difference between the two is that pressure treated lumber will resist the elements better than untreated due to chemical preservatives added, and so will maintain its integrity in conditions that would cause normal wood to rot.
Wood is one of the most common material for use in raised beds. Untreated pine or spruce (whether heat-treated or kiln-dried) are good, inexpensive options. Unlike pressure-treated lumber, untreated or heat-treated wood contains no questionable chemical compounds that may leach into the soil within the bed.
Since it's widely available, fir can be useful for those running a slightly tighter budget. It's one of the cheapest woods for outdoor use. If you're a woodworker or DIY garden furniture maker, this species also works and machines well, in addition to holding finishes easily — whether a clear varnish, stain or paint.
While redwood or teak certainly qualify, five more common lumber species that also stand up well to sunlight, moisture and wood-boring insects are Western red cedar, Spanish cedar, cypress, white oak and mahogany. Red cedar tends to be knotty, but it's affordable and widely available.
Which Wood Lasts the Longest? Teak wood easily lasts the longest when used for outdoor furniture or decking. When properly maintained, it can last for the entirety of your life and years after.
Cedar wood may last over 20 years when used in outdoor structures, such as decks, pergolas, gazebos, or furniture. It can last between 15 and 20 years when used for constructing a fence or support posts.
Boric acid (borate) is one of the most effective fungicides for use in treating wood rot. It can be applied to wood during construction to prevent future rot, or as a treatment to stop an active decay fungus from growing.
With concrete holding the moisture against the wood, wood has no chance and will eventually lose the battle. Now you don't have to lose all hope because it's for certain that the concrete around the post will crack, therefore making it easy to pull out when it starts to rot.
While treated wood has distinct advantages, you might decide that they aren't worth the added health risk. Yet, if you need something to last a long time and you know people won't come into much contact with it, treated lumber might be the better choice.
The longer lifespan of pressure-treated lumber is one of the most significant advantages. Although its lifespan is short compared to composite materials, it will last much longer than untreated wood. Depending on its use, pressure-treated lumber can last up to 40 years when properly cared for.
Pressure-Treated Vs. Untreated Lumber
Pressure-treated lumber is the result of a process that uses high pressure to inject a preservative into the wood. It's a process that extends the longevity of the wood considerably, adding decades to the life of the material.
Untreated Wood
Left in their natural, unfinished state, most woods deteriorate quickly when exposed to outdoor environments. However, there are several species that have naturally occurring chemicals that help them shrug off harsh weather and insects.
Iron oxide stains in wood are usually dark spots caused by prolonged exposure to water and / or metal. The iron oxide reacts with the tannins in the wood and stains it black. Wood can intentionally be stained black in the same way, and that's called Ebonizing.
Wood is a porous material. This means that, over time, exposure to water will permeate the wood's membranes, causing it to rot, soften, and fall apart.
Depending on outside conditions and lumber species and size, air-drying to a desired MC can take from several months to almost a year. Wood stored outdoors and under cover will dry to an approximate moisture content of 12 to 14 percent in western Oregon and 8 to 10 percent in eastern Oregon.
The Need for Deck Ventilation
A lot of people are not aware that just like them, wood also breathes. Wood can expel and absorb moisture. In fact, wood can also move!