Natural wood adds character and warmth to your outdoor spaces, from benches and bridges to garden beds and gazebos. Unfortunately, some fungi and insects love wood as much as you do.
It’s important to choose a durable, weather-resistant wood for exterior use. Some lumber is treated with chemicals to protect the wood and prevent or delay rotting, and some are just naturally more resistant to rot.
No wood is entirely rot-proof, but there is a good number of species that have superior rot resistance and can be used outdoors without chemical treatment. Others are moderately resistant and may require regular or semi-regular treatment to extend their strength against rot.
Natural wood is a lovely choice for adding warmth and texture to garden structures like raised beds, fences, decks and trellises. Much lumber is chemically treated to prevent it from rotting. However, some woods have superior rot resistance naturally and can be used outdoors without chemical treatment.
Cedar, redwood, cypress and other naturally rot-resistant woods are often hailed as the premier choice when building outside structures like decks, arbours or saunas. They have beautiful colour and grain, are often aromatic, and their chemical structure can make them immune to insect and fungal pests.
However, naturally resistant wood species are not guaranteed to last any longer than pressure- or green-treated lumber. Here are some ways to help ensure your natural, beautiful and expensive wood lasts for decades, not years.
In the past, many homes relied on softer woods for their siding, eaves and trim. These woods looked beautiful initially, but as they faced rain, snow and shine, they softened over time.
Unfortunately, many fungal species love softwood and moist environments. So if you live in an older home, you can expect wood rot to show itself regularly. If left unchecked, wood rot can spread until it threatens the structural integrity of your home.
But you don’t have to wait until wood rot destroys your home to make repairs. When you call in an expert to restore your home, you can choose rot-resistant woods that will stay strong and look beautiful for many more years to come.
At Hitch Property Constructions, we offer timber repairs work from simple timber repair to almost new structures, renovations, and extensions.
Why Use Wood Today?
From a design standpoint, wood surfaces are very intriguing, with their colour modulations, weathering and variety of textures. Woods have a huge range of aesthetic expressions, from wild, bumpy log posts to refined decks sanded smooth. Wood has an undeniable warmth and an association with woodlands and natural landscapes, and one type of rot-resistant wood can be used in a variety of ways. From an environmental standpoint, wood is a great choice when it is locally sourced and sustainably harvested.
How Does Wood Get Rotted in the First Place?
Wood lovers must know thine enemy: Fungus. Yes, insects can do some damage, too, but insects are only attracted to wood that is wet and already rotting. Usually, the fungi move in first, then the termites and other wood-destroying insects come along.
The fungi that destroy wood are decay fungus or wood-decay fungus. They are plants that don’t contain chlorophyll. They can’t produce their food by photosynthesis so, to live, they must take their food from other materials. In this case, their food is wood. Decay fungi settle into the wood, and their eating habits destroy the wood’s substance and reduce its strength.
Decay fungi, like most other organisms, require four basic conditions to survive.
Why Some Woods are More Resistant
Why do some woods last well on your porch, while others seem to rot after one season? It has to do with the composition of the tree.
- Amount of sapwood: the wood closest to a tree’s bark is a called its sapwood. On a cross-section of a tree, it’s that light-coloured layer, right before the bark. Sapwood generally does not have much decay-resistance, no matter what type of tree it’s part of. So, if a piece of lumber has a lot of sapwood, it’s going to have a low resistance to decay. And it won’t last long out there.
- Amount of extractives: Extractives in the wood are what give it its colour, scent, and other physical and mechanical properties. They are the waxes, fatty acids, resin acids, and terpenes of a tree. Typically, if a tree grows slowly, it has more extractives and higher decay resistance. So older-growth trees tend to have more natural protection against rot.
Fortunately, you don’t have to be a tree specialist to know which woods to use for the most durability against wood rot. At your local lumber mill or hardware store, an employee familiar with woodworking will likely be able to point you in the right direction.
Before you head out to shop for rot-resistant lumber, it’s good to have an idea of what kind of wood you want. After all, each wood will have different properties aside from resistance and durability, like colour, texture, grain, how easy it is to work with, its availability and, of course, its cost.
The World’s Most Rot-resistant Woods
Not all naturally resilient woods are widely available. For instance, some tropical woods are very decay-resistant. The warmer temperatures and higher moisture levels in the tropics have primed them to withstand decay. These more exotic woods are more expensive and not as easy to pick up at your local store as their more common domestic counterparts.
In order of most-to-least, these are the woods that are resistant to decay and rot damage, along with information about the ease or difficulty of working with it and other physical characteristics of the wood which may make it desirable for particular projects.
Insects and fungi (aka rot) love softwood. Preferably soft, wet wood, which is why you’ll find termite damage in waterlogged areas of an old house. The soft pine, fir and other white woods that are used to construct most homes today provide little protection again termite and rot.
So, why don’t we build houses entirely out of rot-resistant wood? We could, but the cost would be prohibitive. You should start with a rot-resistant wood like the options below and use a few tricks to prevent rot.
There are options for more rot-resistant wood that you can use when making repairs (especially exterior repairs). Interior woodwork like trim and mouldings, hardwood floors, mantles don’t need the protection that exterior elements like siding, exterior trim, porches and decks need.
Here are a few options for some of the most rot-resistant wood you can find and why it might be a good fit for your project. Availability and pricing vary greatly depending on your region. So you’ll have to do a little local research to find what is what in your area.
Moderately Rot Resistant Wood
Here in the southeast, this wood is very abundant. It is very affordable, has great workability and accepts stain and paint very well.
Redwood is to the western US what Cypress is to the southeast. A very affordable locally grown wood that is typically the wood of choice for exterior work.
Pine is not usually a rot-resistant wood, but when you have old-growth pine, you gain a fair amount of resistance. You’ll often find this wood in old shiplap siding and other trim elements on the exterior of old homes.
Check out our range of timber repairs Melbourne at Hitch Property Constructions.
The old-growth version of this resistant wood has so much more heartwood than its new or second-growth cousins that it is harder and has much greater resistance to rot and insects.
Cedar (Eastern White or Western Red)
Cedar is a great wood for exterior work. If you are planning on finishing with a stained cedar excels at this. If you plan to paint, make sure you use a stain-blocking oil primer because the resins in cedar will easily bleed through paint.
White Oak is a very hard, domestic wood that is readily available here in America. It has been used for centuries to build windows, doors, fine furniture and wood flooring.
Once again, the old-growth version of this wood is very resistant to rot and insects.
Probably the most readily available rot-resistant wood in America. It’s at every home store and is very resistant to rot and insects. It can be used in direct contact with the dirt without rotting and holds paint fairly well. Just be sure to wait a few weeks after installing before you paint because it needs to dry out from the chemicals used to treat it. Caution: It does shrink quite a bit once dried.
Extremely Rot-Resistant Wood
This is the king of hardwood. It is extremely dense and hard, which keeps the insects and water at bay, preventing rot. Mahogany is beautiful when finished natural, which is why many doors are built with it. It also holds paint very well. But because of its beautiful characteristics and rot resistance, it can be expensive.
Spanish Cedar looks similar to Mahogany and is also very dense. While not as hard and not nearly as expensive as Mahogany it is a great choice for windows and exterior trim since it is very stable. It’s getting harder and harder to find this wood in recent years, but it may still be available in your area.
A rock hard tropical wood that is fantastic for decks and porches because it is one of the hardest woods around. Its hardness allows the wood to be left natural outdoors with no finish and not rot away. That same hardness makes cutting and machining it very difficult and time-consuming. You’ll need to pre-drill any fasteners because of its hardness.
Like Teak, this wood is hard, hard, hard and is great for decking and porches. Its rich red colour is beautiful outdoors and will last many decades if kept oiled.
This a rather new wood on the market that is said to be nearly rot proof. It is essential Radiata Pine that is treated with a process called Acetylation. This process chemically alters the wood, making it extremely dimensionally stable (won’t shrink or twist), unattractive to insects and extraordinarily rot-resistant. Unlike pressure-treated wood, there are no harsh chemicals used in Accoya. You can learn a little more about Accoya here.
Using Wood Outside
The price for chic outdoor furniture can be justified if your purchase is an investment in products that will weather well over time. Everything rots eventually. And I am sceptical of products that claim extra-long life spans, for I fear they are like the Wonder Bread of outdoor materials, laden with chemicals to prolong their shelf life.
Smooth wood is a fantastic surface for bare feet, which is why it’s so popular as pool decking and for areas near outdoor showers. An experienced builder or carpenter will be well versed in constructing wood elements that do not collect water.
Wood post fences
A wood post fence with rough texture, like this ash juniper post fence, gives a nice handmade look to a home landscape. Wood that is not sanded smooth or shaped into perfect beams creates a casual feel.
Plants growing on a wooden trellis will contribute to the wood’s rotting over time because the plants trap moisture and open the wood up to decay. However, a wooden trellis can have a cottage-garden-style look that is not achievable with a metal trellis. Twining-type vines that wrap around structures, like clematis, are a better choice for a rot-resistant wood trellis because they will not try to attach their roots to the wood.
Resting raised cedar beds on gravel instead of soil is a smart move because the gravel will drain water quickly away from the cedar and does not retain moisture. For the interior of a raised bed, a geotextile or landscape fabric can separate the bedding soil from the wood to wick moisture away from the wood and preserve its longevity.
Wood can be used in the garden as an accent too, not just for the main attraction of a deck or pergola. Ipe and redwood are popular woods for making refined details. Using wood as a special finishing touch on a metal railing or bench is also a way to keep the wood from coming into contact with the ground.
How to Stop or Prevent Rot
Even rot-resistant woods can become vulnerable over time or with extreme conditions. So, how do you stop wood rot in those cases?
If you’re using a block of wood outside, starting with a rot-resistant wood is the most important step. From there:
- Limit ground contact. When a block of wood is in direct contact with the ground, it opens the wood to mould and fungus because it allows moisture to penetrate the wood.
- Pitch the wood so that water does not collect on the surface.
- Remove plants and vines that grow over the wood. They accelerate rot due to moisture.
- Use chemical wood preservatives to deprive fungi of its food source and make wood inedible to decay fungi.
- Keep it painted or stained to help keep out water.
- Remove any standing water.
The more you can keep wood dry, the better you limit the chance of fungus getting a hold on your exterior wood and outdoor furniture. Preventing rot is much easier than stopping it once it gets going.
Pressure-treated lumber is wood that has undergone a process that forces a chemical preservative deep into the wood. The “pressure” part is when the wood product is placed into a large holding tank which is depressurized to remove all air.
A preservative is added to the tank, under high pressure which forces it deep into the wood. The tank is then drained and the remaining preservative reused. The wood is removed from the tank and prepared for shipment to your local lumberyard.
This chemical makes the treated lumber resistant to fungus and insects, which makes the wood more durable. It can then be purchased as lumber, boards, posts and plywood.
A Wood for All Seasons
Pressure-treated lumber makes a great building material for the outdoors all year long. If you’re building or buying a deck, mailbox, swing-set, picnic table or any other exterior wood project or product, you can count on long life from a piece made from pressure-treated lumber.
Is Chemically-treated Wood Safe?
The words “chemically-treated” may make you wonder if this wood is safe for pets, children, for garden use, for interiors and more.
The EPA is currently reevaluating the type of pesticides pumped into pressure-treated woods. These chemicals are chromated arsenicals, which includes chromate copper arsenate (CCA), a type of arsenic – and a carcinogenic. The EPA has already limited many uses of CCA.
Pressure-treated wood is now treated with Alkaline Copper (AC) and Quaternary Ammonium Compounds (ACQ). These compounds are much less toxic and have shown to not leach into soils the way CCA and Creosote have. This does not eliminate health risks but significantly minimizes them.
We have a wide range of Melbourne timber repairs for your home renovations. Check out Hitch Property Constructions.
General Safety Tips for Chemically-treated Wood
- Wash children’s hands after they have been in contact with treated wood
- Do not put food directly on a treated wood surface, like a picnic table.
- Do not use treated wood where it may come into contact with edibles, such as in a garden.
- Never burn treated wood – indoors or outdoors. Burning this type of wood releases chemicals in the ash and smoke.
- Do not use treated wood near livestock, feed, or food-producing animals.
- Do not use treated wood where it may come into contact with drinking water.
- Do not place treated wood or sawdust in a compost bin, and do not use it as mulch.
- Do not use bleaching or cleaning agents such as sodium hypochlorite, sodium hydroxide, sodium percarbonate, citric acid or oxalic acid on treated wood. These can cause the wood to release chemicals that may be inhaled or come in contact with skin.
The main factors that contribute to wood rot are sunlight exposure and moisture. Wood can also come under attack by insects, fungi and other organisms. Using rot-resistant wood outside is especially important when the wood comes in direct contact with the ground, like with a raised garden bed or vine trellis.
Ground contact opens the wood up to mould and fungus because it allows moisture to penetrate the wood, which expands and splits in response. There are methods of construction for avoiding ground contact and for pitching wood so that water does not collect on the surface. Plants and vines that grow over the wood also accelerate rot due to moisture buildup.