Logs Have Dry Rot

Why do log homes develop dry rot?

In a word – WATER.

Moisture in the form of rain or snow is the reason for rot in wood. If your logs have rot – it is caused by water. The way to stop rot is to control the logs’ exposure to water. This is a simple concept but not that simple to actually do!


This short video tells the story about why water splashing off a deck onto logs is the leading cause for rot in this area.

The rot organism needs these ingredients to begin degrading wood:

Logs with dry rot

So many cracks, so much water infiltration- so much rot.

  • Moisture content between 20% and 30% in the wood’s fiber. While this percentage varies from species to species, most wood will start to deteriorate at around 20% moisture.
  • Temperatures between 60º and 90º. This is why most of the active rotting occurs during our hot, humid Midwestern summers.
  • Oxygen – rot needs it to get going. This is why wood that is underwater does not rot. There is not enough “free oxygen” for the process to take place.
  • A food source. In the case of log homes, this means wood, i.e. YOUR HOUSE!

How to keep a log home dry and prevent rot

  1. Maintain a good finish on the exterior logs.
  2. Have adequate overhangs wherever possible. The best way to stop water from getting into the logs is to keep it from falling on the logs in the first place. We recommend at least a 24” overhang on a single story log home and in this case, more is almost invariably better. On some lakeside gable walls for instance, we recommend five to eight feet of overhang. These overhang numbers are the two most important aspects to take into consideration when considering buying a log home. Are there adequate overhangs?
  3. Have gutters in place and keep them working. Gutters often have to be retrofitted to an existing log home in order to keep the water that splashes off the roof to a minimum. The number one cause for having to replace rotten logs is due to splashing water from the roof onto lower logs. Gutters can be a reasonably economic part of the solution to controlling moisture.
  4. Free board – in other words – keep the house up off the ground. Many times, this is a difficult thing to change because it can involve lifting the house and putting it on a new foundation. However, if you are in the design stage of building a log home, it is a relatively simple thing to raise the building above the surrounding ground (above grade) to prevent the water coming off the roof from splashing on to the lower logs. It will also help by preventing scrubs, tree roots, and simple soil moisture from making its way in to the lower logs.
  5. Protect the lower logs around your decks. Water splashing onto lower logs is the #1 cause for log rot. Decks have two ways they put the logs at risk.
    • They reflect UV light and heat from the sun onto the logs, which in turn, causes finishes to breakdown faster.
    • They deflect water (splash) onto the logs effectively negating the “free board”.

    If you would like to know how to properly flash a frame deck to a log wall, check out this drawing. File download: How to Flash a Frame Deck to a Log Wall PDF

    If you are in the design stage, we recommend having a limited amount of deck around a log home. Think about what deck space you are going to actually use and build those. On the decks that you do build or already have, make sure they are properly flashed between the logs and the deck itself.

    Keep in mind that while the logs elsewhere on the home are going to be re-stained every 2-6 years, the logs behind the deck are never going to get another coat unless the deck is removed. The area where the deck comes in contact with the logs must be completely sealed or it will rot.

  6. The caulking and chinking between the log joints must be in good condition.
  7. Keep objects away from the logs to avoid water splashing back on them.
    Keep accessories, utilities, propane/oil tanks, woodpiles and other items away from your log home. While at first glance the convenience of placing these items under the cover of the eves of the house may seem like a good idea, it is not good for the logs. For one reason, the object may protrude out into the drip line causing water to splash back – wetting the logs.Secondly, when the rain stops, these areas aren’t allowed to dry out quickly because of being blocked from the free flow of air around the logs. Logs that are constantly wet puts stress on whatever type of finish is on the logs and can cause this finish to breakdown faster. While it is certainly a difficult task, try your best to keep these items away from your logs. Keep the logs dry.
  8. Pay particular attention to windowsills. Pay particular attention to the logs underneath windows and to log rot below windows. Make sure this seal is complete. Windows tend to concentrate water on the logs directly below them so it is very important to keep a close eye on these areas.Make sure that up-facing checks over 3/16″ are filled with caulking. Secondly, make sure the seal between the bottom of the window and the top of the log is tight. If there is a sill formed on the top of this lower log, make sure that it pitches water away from the window.
  9. Give your log home a checkup

Edmunds & Company has been helping people in the Midwest with dry rot repairs for over 30 years. Give us a call at 715-373-5744 or email info@restorelogs.com

There is a lot to consider here. For over 30 years, Edmunds & Company has been helping customers repair all types of problems with their log homes. Get your questions answered by calling 715-373-5744 or contact us.