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DayCreek Journal

June 1 , 2011


Paper Enhanced Mortar (PEM) Update

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Here’s an example of how the mortar looks after 10 years. After the mortar was tuck-pointed with a bread knife, a small foam brush was used to finish off the mortar.
It’s been 10 years now since we started construction on the exterior cordwood walls of our house. During those 10 years, the walls have gotten a pretty good beating from wind, rain and sun even with our hefty 3-foot overhangs on both floors. Doing due diligence, I took a stroll around both floors of our house and carefully looked at each and every external wall. My goal was to find any signs of degradation of the mortar.

Looking at the walls the only sign of any degradation that I could find were a few pits in the mortar where chunks of paper once existed. My guess is that I must have been in a hurry to make slurry and the paper was not totally broken down into very fine pieces.

This in itself was only half of the problem because the small paper chunks would have stayed in place if it not were for my dear friends…the woodpeckers! (I have an agreement with our local woodpeckers: I keep them in suet and they keep me from yelling at them to stay off the house!) These pits are only on a few walls and are very small and not deep. You would have to look hard to find them.

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Here’s the worst-case degradation of the PEM that I could find on the house. Just a few divots taken out by woodpeckers looking for food. Notice that there is no shrinkage of the mortar next to the frame post.

Besides the slight degradation, there are the occasional shrinkage cracks – not nearly as many as I experienced with sawdust-based mortar. They are very minor and of no concern.

I realize that 10 years is not 100 years, but I do not see any reason why PEM cannot last 100 years or more based on the condition of our exterior walls as they are today. I do want to stress however that our house is supported by the walls and a post and beam frame. PEM does not have the same compression strength as regular mortar and to have it bear the entire house-load is still in question. Until some rich kid comes along and can afford to have the wall tested for compression, the verdict is still out on compression strength of PEM.

The complete article on PEM can be found in the 2011 Continental Cordwood Papers on sale now! To order please click here.

—Alan Stankevitz