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DayCreek Journal

October 26, 2003

The Rice Krispies® Effect

Photograph courtesy of The Imaginary World

Lately I've had a hankerin' for Rice Krispies® and I just can't figure out why. Could it be that the cordwood walls have been talking to me again? Yes, those three strange sounds once heard while building one of the first walls are back: Snap, Crackle and Pop. (See the June 1, 2001 Journal for the first encounter with those strange noises.)

But this time I am absolutely certain what is causing those sounds. It is a rather rare phenomena to be sure since I have only encountered it two or three times. This time, it was under a controlled condition so I know for sure what caused the sounds.

It all started with my arrival at the house after being gone for three days. The house was closed up tight and the outdoor temperatures soared into the low 80's (F). I opened the door to the house and immediately found myself deep in the Amazon jungle (well, it felt like it anyway). The humidity levels were quite high due to the freshly mortared cordwood walls.

So the first thing I did was to open up all the windows. There wasn't much of a breeze going on, so the humidity levels in the house dropped rather slowly at first. By 2 PM, a dry front came through and the winds picked up and the outdoor humidity levels dropped like a rock. By 3 PM, the outdoor humidity was at 22% with a temperature of 82°(F) and the winds were gusting to 30 MPH. With the windows wide open, humidity levels began to drop inside the house as well.

Shortly afterward the front passed the sounds began. At first the sound reminded me of those pesky Asian lady beetles crashing into the windows, but as I listened intently it sounded like Rice Krispies®. I walked up to the walls that I freshly mortared and I could hear the sound was coming from the individual logs. Adding to the chorus, were the logs just laying there on the floor. The sounds continued well into the evening.

Visually, very small checks began to appear in some of the wood pieces. These checks are so small that they do not penetrate through the entire log like the main checks. They only appear to be a few centimeters deep. It doesn't seem to matter if the logs are split or round, pine or cedar they will all eventually do this. I have noticed these same "micro checks" in close-up photographs of cordwood walls. It's just the natural drying process of the wall and when humidity levels drop rapidly, you can hear the Rice Krispies® Effect.

This really brings to light how wood expands and contracts. An example of the process is the swelling/contraction that occurs with solid wood doors. That is why doors stick in the summer while closing freely during the winter months. Wood naturally expands and contracts based on humidity levels.

I remember Rob Roy telling me about a fellow cordwood builder in Texas that heard a sound that he thought was caused by bugs munching on his cordwood walls. The sound was only heard for a short period of time and never heard again. I now wonder if it was caused by the Rice Krispies® Effect? Texas is known for rapid humidity changes. (Gotta love those dry fronts that sometimes spawn tornadoes.)

Cordwood Wall-O-Meter at 48

Hard to believe, but 75% of the cordwood walls have been completed. Only 16 more walls need to be completed before I reach "cordwood nirvana." Hopefully in another year all 64 walls will be completed.

The last two walls to be completed this season were the walls directly in back of the wood stove. The way the weather is looking, I might have to fire up the stove soon now that we're headed for the two cloudiest months out of the year. So far though, the solar heated sand bed has been doing its job but times are a changin' and we may see our first snow flakes this coming week. I am anxious to see how this winter compares to last winter regarding heat demand. With sixteen walls completed on the interior of the house, the temperature shouldn't fluctuate as much from day to day. The downside compared to last year is that the windows are no longer sealed with a layer of 6 mil plastic. Last winter, the windows stayed sealed after the foam was sprayed leaving the house virtually air tight. There will definitely be some air infiltration through the windows, but how much is the question. We'll just have to wait and see.

Mortar Cracks Fixed?
The verdict is still out, but the last four window walls were built by completing the cordwood work first, and then plastering the window wells. By reversing the construction process, I hope this will fix the mortar shrinkage problem that has caused a few cracks around the perimeter of the window. This new process seems to make sense. The cordwood walls take quite a bit longer to dry out compared to the window frames. By building the cordwood walls first, the mortar joint between the window plaster and the cordwood wall appears to bond together better. Previous to this, I found that the by the time I had built the cordwood walls up adjacent to the plastered window, the mortar had already dried out to the point where the bond didn't seem as strong. I will have to wait until the walls are completely dry, before knowing if this process works best.

This coming week I hope to install ceiling fans and maybe bring in a few wheel barrows worth of sand and clay into the house so I can do some plastering over the winter months. I think my dry walling days are over now that I've fallen in love with Paper Enhanced Plaster (PEP).

That's about it from Day Creek.

The Milky Way is still viewable after dusk, but it's slowly sinking towards the southwest horizon.