Choosing Rot Resistant Wood

Old 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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by Scott Sidler

I'm a historic preservationist and licensed contractor. I help old house lovers understand & restore their homes so they can enjoy the history and character that surrounds them more everyday! When not working, writing or teaching about old houses I spend most of my time fixing up my own 1929 bungalow with my wife Delores and sons Charley and Jude.

http://www.AustinHomeRestorations.com

26 comments

  1. Sheila on said:

    We are getting all wood windows for our addition to our 1918 house (that has original windows, which we love). Seems like most manufacturers use either Pine from the Northwest, but some (more expensive) use Douglas fir. Is there an advantage to Douglas fir over pine? Thanks! Sheila

  2. P Kott on said:

    We are having a custom new-old window made for our 1928 home in upstate NY. It’ll be protected somewhat under a covered porch on the north side of the house. The craftsman who will build it is saying eastern white pine is sufficient to prevent decay, but will make it out of mahogany if we like. We believe the existing old windows, which are very heavy and have leaded glass divided panes, are originally mahogany. May I ask your thoughts on EWP vs. Mahogany?

    • EWP is a pretty common wood that old windows in the northeast were built with. Old growth EWP will yield better results because it is more rot resistant than the kind we have available today. If your original windows are Mahogany and have lasted close to 90 years I would stick with the same wood. Mahogany is extremely rot resistant and very stable so it will help paint to last longer as well. If you can afford it go with Mahogany.

  3. Tom Anderson on said:

    Please advise best techniques for repainting virgin Louisiana Cypress home (exterior ). Home build in 1906 with some of the finest La. cypress by the owner in charge of the cypress company at that time.

  4. a fan of Hays Town on said:

    Hey,

    Where can I find old-growth cypress clapboard for home repairs? I went to 2 local hardware/lumber stores, and neither one has clapboard. In fact, one of the stores has never heard of clapboard! I am in the rural southeast area of the US. Would Home Depot carry old-growth cypress CLAPBOARD?

    Thanks,
    an owner of an A. Hays Town house (built a little more than half a century ago)

    • Old-growth cypress is not something you’ll find at Home Depot or Lowe’s. It will have to be sourced from architectural salvage yards or companies like Goodwin Heart Pine the remill reclaimed old-growth lumber into new woodworking materials.
      And clapboard is a New England term it seems to me. I don’t hear a lot of southerners use it. Normally it’s called bevel siding down here. Although true clapboard didn’t use to have a bevel in it at all.

      • A fan of A. Hays Town on said:

        Hi,

        I just found a store that does architectural salvage. http://www.circa1857.com.

        They have old cypress clapboard…here’s my question: when I buy cypress from them, how will I know whether or not I have the real thing? Is there a way to tell the difference between old cypress and new cypress?

        Many thanks for the info you gave me yesterday which was wonderfully helpful!

          • a fan of A. Hays Town on said:

            Hi,

            I have a house that was designed by A. Hays Town in 1960…in southeast Louisiana. A lot of work needs to be done on it…like painting. fixing the dry rot, floorwork, etc.

            Most of the painters/contractors in my rural hometown have never heard of A. Hays Town (a regionally famous architect) so they do not understand how to work with this house.

            I want to adhere to the architectural vision of Mr. Town..a.nd use the same materials as much as possible and stay with the same design.

            It’s hard for me to find specifically oriented craftsmen/painters/contractors in my area. I know that there are a lot of contractors, but most of the ones in my area have never heard of A. Hays Town.

            So how do I find specifically oriented craftsmen? Ideally, I would love to work with craftsmen who love the work of Mr. Town.

            I did find a store called Circa 1857 that’s in the nearest big city. They told me they have cypress clapboard, etc, and it’s old growth.

            Any suggestions? You have been wonderfully helpful so far! I really, really appreciate your help. 🙂

            Many thanks,
            a Louisiana homeowner

  5. JohnG on said:

    Hello,

    I have been vasilating on the best way to repair some rotten cypress siding on our home. It was built in 1972 and sided with vertical board on board cypress (5/4 x 8). Charleton SC.

    I have gotten different advice from several contractors. Some say use Cypress for the repairs others say use pressure treated rough sawn. Once painted they say you can’t tell the difference. And given the pressure treated cost less it makes more sense.

    However, as you mentioned above, the pressure treated can shrink causing the repaired spots to bow or move around. One contractor said it would be a big mistake to not use Cypress because of warping.

    Looking for more informed input on which wood to use.

    Also should not that goal is to repair the home and either sell or do a major renovation is 5 years or so. If we do the reno all the siding will be replaced. So for now repair needs to be just good enough. Not great. It will all be painted.

    Thank you.

    • John, look into Accoya for the replacement wood. It is extremely rot resistant and won’t shrink, cup or twist like pressure treated.

      • John on said:

        Thanks Scott. I will look into Accoya. Can you suggest a suplier in the SE? I am ok taking a road trip for the right product.

        Thanks Again.

        John

  6. Tropical hardwoods are wonderful, and for anything made out of them and stained or varnished to allow for the unique grains and color to show, I’d only use like woods for repairs or replacement. However, for most homes that have painted windows and trim, I’ve found Accoya to be an excellent alternative that doesn’t exacerbate concerns about unsustainable harvesting of tropical forests. It’s dimensional stability alone is reason enough to choose it for doors and windows, since it doesn’t expand and contract with changes in moisture levels.

    All of the windows in our old home were original except one unfortunate aluminum window in our kitchen that faced onto the street, destroying the integrity of the home’s architectural character. We had it replaced with an appropriate set of casements separated by a decorative fixed window. That windows caused us nothing but grief. They swelled shut during winter rains, summer marine fog and worse, they leaked terribly, needed constant repainting and had already begin to mold and accept termites. So three and half years ago we replaced them with a unit made of Accoya, again custom made to replicate our other original 90 year old windows. On a Spanish revival home like ours, there are no overhangs to protect windows from the elements, yet this set has remained undeterred by changes in temperature, repetitive days of rain, ocean fog or our extremely dry, warm Santa Ana wind events. They open and shut just as easily as new, the paint still looks new and they seal well. Also, the wood is strong enough that the mullions and rails can match the exact dimensional qualities of our original windows.

    I really hope this product catches on to combat the vinyl window scourge attacking the integrity of our historic districts and other vintage properties in the US and around the world.

    • I’m a big fan of Accoya for the very same reasons John. Good stuff!

      • Glad to hear you think so. I’ve found that it’s not well known; except for my window guy, I end up educating most contractors and craftsman I meet. Really hoping they can ramp up availability and advertising so it can become more readily recognized as a desirable resource in our historic districts.

  7. Roxanne on said:

    I have a new home not built to code and water intrusion. The outer shell was removed and some studs were marked for replacement. Is it possible to have wood rot that you cannot see from the outside, for instance the back of the studs? Thank you for any advice

    • Roxanne, sorry you’re dealing with that. Any wood rot will begin on the surface of the studs and be visible if the outer shell was removed. With the water damage it is typical to remove any of the water logged materials for the risk of mold even if there wasn’t rot. A thorough inspection by a pro should be able to determine where the rot is though.

      • Roxanne on said:

        Thanks for your quick response Scott. I have two more questions, lots of mold has been removed on the studs. They have not gone into areas from inside the house where there are cabinets / tubs.
        Would there be an issue if all mold wasn’t removed on the studs? Looking inwards from the shell removed, would they be able to see all mold?

        • Mold can continue to grow even if the water source has been removed. Materials don’t always have to be removed but they should at minimum be treated to ensure the mold has been killed. That being said I’m not a mold remediation specialist, so check with an expert in your area to be sure.

  8. Glenda on said:

    Repair question:
    My brother and I own a commercial 50 year old concrete block building. It has extensive alligatoring along the joints between the block. Which product would you recommend to repair this building?
    Repair Missouri

  9. Pansy Benson on said:

    Thanks for writing. Woods from different tree species vary greatly in their resistance to decay. wood floor repair nyc

  10. Mike on said:

    Mahogany – This is the king of hardwood.
    Which Mahogany? I used African to build my new front door. Will it work well for window sash and storm windows?

    • Mahogany will work great for windows except that they will be crazy heavy which will mean bigger weights and depending on the size of the sashes maybe even sash chains instead of cords. Redwood is good in the northwest. Cypress in the southeast. Find what’s available, rot resistant and stable in your local area.

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