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Choosing Rot Resistant Wood

Choosing Rot Resistant WoodOld houses are constantly having to deal with wood rot and insect damage. While the old-growth wood used in houses built before the turn of the 20th Century are a more rot resistant wood than anything available today, no wood is rot or insect proof. 

Insects and fungi (aka rot) love soft wood. Preferably soft, wet wood, which is why you’ll find termite damage in water logged 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 moldings, 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 varies 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

  • Cypress – Here in the southeast, this wood is very abundant. It is very affordable, has great workability and accepts stain and paint very well.
  • Redwood – 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.
  • Old-Growth Pine – 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.

Rot-Resistant Wood

  • Old-Growth Cypress – 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 stain cedar really 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 – 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.
  • Old-Growth Redwood – Once again, the old-growth version of this wood is very resistant to rot and insects.
  • Pressure-Treated Pine – 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

  • Mahogany – 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 – 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.
  • Teak – 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.
  • Ipe – Like Teak, this wood is hard, hard, hard and is great for decking and porches. It’s rich red color is beautiful outdoors and will last many decades if kept oiled.
  • Accoya – 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.

Whatever your need, there is a rot resistant wood for your project. Search your local lumber yard for what is available in your area. If you already have a favorite, I’d love to know what it is and why in the comments.

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51 thoughts on “Choosing Rot Resistant Wood

  1. It caught my attention when you explained that pressure-treated pine timber can contact dirt directly without any risk of rotting. My sister is looking for some landscaping material she can use to create a border around the large backyard garden she’s planning. I’m glad I read your article so I can let her know why treated timber would be beneficial in her situation!

  2. When using cedar to make a raised garden bed, do you recommend putting anything on the cedar (wood) to make it even more rot resistant, or is that overkill?
    Thank you

  3. I’ve used Thermory siding before. Specifically, I used their ash siding (not their alder). It was gorgeous clear wood. It had a dark brown color at first, but it slowly fades to a silvery gray (over a 2+/- year period). It’s possible to apply a finish to keep the original brown color, but it is intended to go gray over time. I actually like the gray color and it is great that it does not require any maintenance whatsoever. The material cost is definitely higher than other typical wood siding options, but if you factor in not having to stain or maintain the wood, the cost seems more reasonable.

    They make decking as well, and it is a great (and more sustainable) alternative to tropical hardwoods.

  4. What are your thoughts about ‘Thermory’ and ‘Cambia’ and other thermally modified woods? They are supposed to last for decades without any additional treatment.

  5. Thank you for this post. They are old houses constantly having to deal with wood rot damages. I will sharing in this post.

  6. I was told by the company that built my fence that the caps were mahogany. I did not treat and 1 year later, the caps are pretty much white now. Should this happen to mahogany exposed to sun and water or is it that it truly isn’t mahogany?

    1. Yes. Mahogany will bleach out in direct sunlight. It can be sanded down to fresh wood and then oiled with something like ipe oil. They will need oil once or twice per year depending on how much sunlight they get.
      I built a deck on the north side of my house this year. Used mahogany for the decking. I noticed a bit of bleaching as I have not had time to sand and oil. I’ll be sanding and oiling next summer. I happened to find a short piece of decking that sat out all summer in the grass. Rain, sun, it was a whitish grey. So I sanded and oiled as a test. Looks better than it did when I purchased it.

  7. I and my friend want to build a small house maybe 3/4 or 1/2 underground. But the land he owns has a lot of small streams and when we started to dig we saw water a few days later at the bottom we dug like a 1 or 2 down. So I want some wood that can keep the water out and to last a long time. What wood should I get?

    1. Build on higher ground. I wouldn’t even attempt to do that. You will hate yourself for doing it in obvious high water table conditions. You will be constantly battling water leaks. The houses I see that you want to build are usually built into the side of a hill far away from any body of water. Or use concrete.

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