Posts Tagged ‘why do logs rot’

Log home dry rot is a bit of a misnomer

A log with dry rot.Log home dry rot is not uncommon in log buildings. One of the most common complaints from log homeowners is that their logs have “dry rot”. Whether the rot is dry or wet, rot equals decay and that is a serious problem in log buildings.

Rot can lead to the need for replacing part or all of the log. There are several factors that can contribute to a log getting rot, but they all have to do with moisture getting into the wood. When wood fibers have a constant moisture level between 14-20%, wood will start to rot.

Simply put - rot is caused by moisture, even though it may appear to be dry. There are several factors that contribute to log home dry rot. Learn more about why logs rot.

Related links:

Rot at the bottom of vertical logs
Rot at the bottom of posts
Repairing rot on lodge pole pine cabin

Log home maintenance you can do yourself – caulking cracks in your logs

Log home maintenance issues sometimes need to be resolved by experts. That is where we come in. But there are also things that the homeowners can do to insure that their logs stay “healthy”.

Up-facing check in log

Classic example of up-facing checks needing caulking.

Logs naturally do develop some cracks or checks. As wood dries, the difference in surface tension and moisture gradients between the inner and the outer parts of the logs cause checks. This is  part of the charm of the log home.

These cracks can face up or down, depending on where they are on a log. Logs with cracks that face upward can be susceptible to rot because they allow the water to travel deep into the logs, where rot starts. The more exterior areas of logs can usually dry out after a rain because of the wind and sun, but the more interior areas can remain wet longer. When this happens, they can reach the right moisture point that allows rot fungi to grow.

Here are the three criteria we generally use when determining if it is necessary to caulk checks on log homes:

  • Face upward
  • Are more than a ¼” in width at the surface of the log
  • Are in a vulnerable place in the wall  (i.e. the bottom courses of a log wall near the ground, an area that gets a significant amount of water splashing up from the ground

If all these criteria are met then the check needs to be filled.

Proper log home maintenance is your best insurance against needing more costly repairs down the road.

Related links:

Log home maintenance
Chinking and caulking
Log rot

Covering up rotten logs – good or bad idea?

Question: I have a home where the floor beams rotted. I ground off as much of the rot as I could and then I treated them heavily with a borate solution. Next, I sprayed foam insulation over them to seal them off. Do I need to be concerned that they will continue to rot despite my efforts?

Answer: Rot is all about moisture. Sometimes when it comes to the practicalities of doing repairs like yours, one has to leave some rot.  The most important thing to its longevity is to keep that area as dry as possible.  So… it sounds like you are on the right track.  The only thing you might find is that some of the rotted areas could attract carpenter ants and/or powder post beetles.  The borate treatment you used might help this but if the wood boring insects get really annoying, then you need to have an exterminator come in and treat these areas as well.  Good luck.

Log home repair and WATER – what’s the connection?

In the simplest of terms – logs rot because of WATER! It seems like a simple concept but the solution to keep logs from getting too much moisture in them is anything but simple.

We spend a good deal of our time helping customers remedy problems they are having with rot that is directly caused by the fact that some of their logs have been allowed to stay too wet over time.

So what’s the big deal with too much moisture in the logs? In a word – ROT! The rot organism needs four ingredients to begin degrading wood.

It needs:

  1. 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.
  2. Temperatures between 60º and 90º. This is why most of the active rotting occurs during our hot, humid summers.
  3. 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.
  4. A food source. This is what the rot organism eats – in this case the wood in your house.

Rot needs all these things to get established. If we can eliminate one of these ‘ingredients’ we can stop the rot process, which is easier said than done.

It is impossible to change the temperatures away from being 60-90° in the summer. As living organisms ourselves, we need oxygen too, just like rot. Rot eating wood is one of the laws of nature, so the only factor that we can control is the moisture content, i.e. WATER! (more…)