Fungus Among Us

On my return trip this week I was greeted by a tree blocking my way up to the house. It was a dead elm that probably should have been cut down a while ago, but it looked like a “widow maker” to me, so it just stood there until a strong summer storm brought it down. I trekked the groceries up to the house and returned with the Bobcat to push the tree out of the way. It was a minor inconvenience, but a reminder of the storms that swept through the area over the 4th of July weekend.

The past week has brought some very strong straight-line winds through the area and for the first time since the house has been built, the exterior walls (even with a 3′ overhang) were quite soaked with driving rains—seven feet up the wall. The force of 60 mph winds with heavy rain were enough to push some water in through the wall along one of the 16 beams that penetrate the exterior of the house. I temporarily put up some flashing where the post and beams meet, but I may end up putting some other sealant at the joints to prevent this from happening again.

It has rained every day for the past seven days and with lots of humidity in the air, I discovered mold growing on the edge of some the logs mortared in the walls. This problem seems to occur most often when I am away from the house for two to three days. Although the cupola is open, the windows are kept shut in case of bad storms and thus, the house doesn’t get a chance to breath very well. Also, over the past month, I have been erecting one cordwood wall per week which has added a lot of humidity to the house to say the least.

To remedy the situation I have taken the following steps:

(1) Sprayed the walls with an anti-fungal agent. This remedied the situation within hours, but it’s treating the symptom and not the cause.

(2) I purchased a portable air conditioner to treat the cause. Portable air conditioners are a bit pricier than window units, but can be moved to any room at any time and also double as a dehumidifier during cooler weather. I really hated to make the investment, but felt it was a prudent step to keep humidity levels down while doing interior cordwood work during the summer months.

(3) I took a week off from doing any cordwood work. Giving the walls a chance to dry, while not inducing any further moisture was a big help.

Before leaving for home yesterday, I inspected the walls and I’m happy to report that all of the walls are looking good. The walls have dried out quite a bit now, and next week I’ll be working on the master bedroom area.

Building 24″ Window Frames
After contemplating numerous methods of erecting the interior window frames, Tom and I came up with a method that works just great! It doesn’t require jacks, braces or straps to mount the internal 2″x10″ window frame. All it requires is 1/2″ sheathing, such as plywood or OSB chipboard. Let me explain.

If you recall, the exterior window frames are made from green-treated 2x10 boards. These frames are locked into the exterior walls and quite sturdy. (The cordwood walls are 8″ thick, making 2 x 10’s a natural choice for the frame width.) My plans have always been to run a piece of sheathing between the exterior window frame and the interior window frame, creating a 24″ deep window well. The idea is fasten the sheathing to the INSIDE of the two window frames, not the outside of the frames. The windows have a wide boarder that allows plenty of room for sheathing and some form of a wall finish to be applied without interfering with the glass panes.

After discussing various ways in which to suspend the interior window frame, Tom and I decided to “hang” the interior window frame onto a box created from 1/2″ plywood that was firmly attached to the exterior window frame. The plywood frame is very strong once screwed into the outer window frame, and it easily supports my weight.

The advantages to constructing the window frame in this manner are numerous. First, it allows me to construct the window frames all by my lonesome. (The 4′ x 6′ window frame is easy enough for me to raise into place.) Second, it allows me to adjust the 2″ x 10″ frame so that it’s flush and plumb. Thirdly, it takes very little time to build and install the interior window frames.

Pictured here are the shelves that I constructed years ago. The shelves are constructed out of plywood, wrapped in roofing felt followed by metal lath and then covered with three coats of plaster. The finish coat was made with type S hydrated lime and white silica sand.

Plaster Shelves Déja Vu
Now that the window frame was “roughed-in” I wondered how I would finish off the interior. Originally, I considered using pine car siding but using wood in areas that get a lot of sun tend to put a lot of wear on wood finishes.
Pictured here are the shelves that I constructed years ago. The shelves are constructed out of plywood, wrapped in roofing felt followed by metal lath and then covered with three coats of plaster. The finish coat was made with type S hydrated lime and white silica sand.

Another thought that entered my mind was to plaster the window frame. I reminisced about the time I built a wall of adobe-style book shelves. I remember quite distinctly saying I would never do that again—way too time consuming and too much work! In retrospect, it wasn’t really that bad. (At least compared to building a double-wall cordwood house.) So why not give it a try? I could cover the window frame with metal lath and use PEP (Paper Enhanced Plaster). It should blend right in with the cordwood wall.
Here’s a picture of the window, wrapped in metal lath ready for the plaster.

Throwing caution to the wind, I’ve decided to give it a try. So off to the store I went to get metal lath and gutter screening. The metal lath is used to cover the window frame and is also formed to round the outside corners. I use the gutter screening to form the inside corners. The rounded corners is what gives the object an adobe-style look.

Here’s a picture of the window, wrapped in metal lath ready for the plaster.

Before applying the metal lath, I cover the entire plywood surface with roofing felt. I’m sure that plastic will work too, but roofing felt holds better and it’s easier to finish off the corners. The idea is to prevent the wood from wicking too much moisture away from the plaster as it dries.

When I did my bookcase, I used the three-coat plaster method: scratch, brown and finish. I’m going to try this time to add all three coats at the same time. I know the sides will work using PEP (Paper Enhanced Plaster), but I’m not sure about the top. I may need to put two coats on thanks to gravity. We shall see.

Having windows that are 4′ x 6′ makes the window frames quite suitable for a seating area, so instead of having a plaster sill, tile seems a logical choice. It just so happens that I have quite a few terra-cotta tiles left over from another project. This should make a nice windowsill. Having a tiled sill will also store heat from the sun, something I’m sure our cats will love.

Clay Plaster Update

The sample clay mixes have all pretty much dried out now and all mixes have not cracked whatsoever. All of the plasters (except mix #5) stayed pliable until they dried. I tried various mixes of clay, paper and lime and all of them seem to be quite durable, but they do leave a powder on my fingers when rubbed excessively. The only exception to this is mix #5 that has portland cement. The portland cement mix hardened within two days and leaves no noticeable powder when rubbed. From what I have read, mixes made from lime gradually harden over time (months to years). Maybe after months of strengthening, these plasters may be as durable as the mix containing portland cement. As a side note, the lime finish coat that I used on the plaster shelves that I built years ago, has held up beautifully.

Pictured above are the five mixes that are now almost completely dried out. The sample on the far right is the PEM mix that’s been used to build the cordwood walls. Notice how much whiter it looks without clay added to the mix.

Here are the proportions that were used to create the samples, pictured from left to right:

Mix #1:
1 part paper, 1 part clay

Mix #2:
2 parts paper, 2 parts clay, 1 part hydrated lime

Mix #3:
1 part paper, 1 part clay, 1 part hydrated lime

Mix #4:
4 parts paper, 3 parts clay, 2 parts sand, 1 part hydrated lime

Mix #5:
4 parts paper, 4 parts clay, 1 part portland cement, 1 part hydrated lime

For the master bedroom, I would like to use the same mix for both the cordwood walls and other plaster walls. My current thinking is to add a bit of clay to the PEM mix that I have been using and reduce the sand by an equal proportion. This should make the mix a bit smoother and add a bit of color to the mix. If the walls turn out as nice as I think they will, I will probably continue with this mix throughout the remainder of the house.

Maybe by the time I complete the walls, I will have dug enough clay out from the hill in back of the house for the root cellar!

A Common Yellowthroat sings away on a fence post.