Dan Chiras

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since Apr 16, 2014
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Recent posts by Dan Chiras

Jonathan,

I have never used whey in a plaster...so can't comment. I wanted to share something that a friend of mine from New Mexico taught me. He learned this technique from Pueblo Indians...I've never tried it, but I did want to share it with you. They apparently add cactus juice, that is, the gooey stuff inside cacti and succulents, to finish plasters...and according to them, it helps create a water proof plaster. I've never tried it, but it is interesting.

I would experiment with adding lime to an earthen plaster to create a more water resistant outer layer, although, the shed roof will give you bomb proof protection.
4 years ago
Hi Kim:

The difference between a finish plaster and an alis is not only the liquid, alises are more liquid, but the ratio of clay to sand. An alis is typically a 1:1 mix. A finish plaster is 1 part clay to two parts sand...usually. I use powdered milk for both alises and finish plasters.

I have no experience adding mica to a flour paste and applying it on a finished surface. Interesting idea, but just don't know anything about it.

I add mica directly to alises and finish plasters. Remember to reduce the sand content proportionately. You can easily replace one fourth of the sand with mica. Again, Kim, experiment first to see what works best.

Dan

4 years ago
Boy, I wish I could help but this is out of my range of experience...Anyone else want to weigh in on this? Dan
4 years ago
Hi Paul,

I think it would be wise to figure out ways to prevent moisture from building up in the soil under your floor. You can seal it all you want, but until you eliminate the water seeping in under your home, you'll never solve it. In other words, let's go to the root cause, and address it, and not put a band aid on it, treating the symptom better sealer.

What can you do? I don't know the specifics of your home, so here's a list of things to consider and/or do if you haven't already done so: (1) be sure to install gutters and drain the roof water 10 to 20 feet away from your home by attaching hose or pipe to your down spouts, (2) dig up around your foundation and install a French drain, (3) be sure that the soil around your home slopes away from the house everywhere, so water naturally flows away from the building and not under it, and (4) if your home is on a slope, you may have to install a berm to move surface moisture (rainwater runoff) away from the building. Try these things and see if they help alleviate the underlying root cause.

Hope these help.

Dan
4 years ago
Hi Valerie...When it comes to foundations other than those made of concrete, I would argue that we don't have many really good choices. There are a lot of options, but really excellent long lasting foundation designs are, in my opinion, few and far between. I think the best option, bar none, is a stone foundation. If you want to avoid using cement mortar, you can dry stack the foundation. That said, stone foundations are hard work and take a lot of stone and a lot of skill. It's a job reserved for the patient and anal among us...or for a professional.

Foundation choice also depends on climate. Earthbag foundations can work fine, but be sure to fill the first two courses with rock and keep moisture away from the foundation walls. These are really great in dry climates. Rammed earth tire foundations are fine, too.

One of the most important things to remember when building a foundation is that you want to prevent moisture from entering the foundation and moving by capillary action into the bottom of your walls, be they dirt or straw bale.
4 years ago
Hi Kim...You can achieve a very smooth, almost sensuous to touch, finish by troweling on a finish plaster but working it pretty hard with a steel trowel. We make a finish plaster out of powdered clay and fine-grained silica sand, in a ratio of about 1 part clay to two parts sand. You can substitute powdered silica sand for a really smooth finish. The secret, though, in my experience is that the results come from trowel work. You need to work the finish coat, smoothing it out pretty quickly after you apply it...so don't get too far ahead of yourself, or have someone following up a person putting the finish plaster on the wall. If you make the mix a little wetter, it gives you a bit more time to work it. You can also burnish the finish plaster with a lid to a yoghurt container, describing circles with the lid.

That said, you can achieve the same results with an alis. That word, by the way, comes from alisandro, the Spanish name for the ladies who used to do the plaster work. We make alises with a 50:50 mix of powdered clay and fine-grained silica sand. Instead of adding water, we use powdered milk, diluted by 50%. In other words, add twice as much water as the recipe for preparing "drinkable" mild.

Be sure to experiment with mixes and techniques before you start working on a wall so you know what you are doing and can do a superb job on the finished wall. Keep in mind, too, that it takes a long time to really master finish coats. I still feel like I'm learning and I've been at it for a lot of year.

Hope this helps.

Dan
4 years ago
Hi Mike...You must have moisture sensors in your straw bale walls, no? I've been told by others in the straw bale "business" that humidity levels as high as 20 to 25% won't cause harm...They say that's natural, they say. The important distinction here is, I think, that the straw bale moisture content cycles and will lower. If that's the case, I would suspect that there wouldn't be much trouble with mold forming. Now, I say this without any empirical data to back up my stance. That's the problem with so many issues in natural building. There is just not enough science to back up claims. The old idea that straw bale and earthen plaster walls breathes is one of the myths. Moisture moves very slowly and at extremely small quantities directly through plaster. Where most moisture enters is improper flashing and penetrations...that is, where electrical wires and plumbing penetrates a wall. To control the amount of moisture entering a wall we really need to pay close attention to moisture moving up through foundations, moisture entering through inadequate flashing, and through penetrations. Be sure to seal all penetrations.

I've been told and I've stated it in my various books on natural building that clay in earthen plasters is hygroscopic and will help draw moisture out of straw bales. If your walls are already plastered with earthen plaster, there's not much you can do. If straw bale walls are finished with cement plaster, that will trap moisture in the walls. In such instances, it's probably worth removing the cement plaster and replacing it with earthen plaster.

Hope this helps...if even just a little bit.

Dan
4 years ago
Hi David,

Unfortunately, I doubt that natural plasters, including lime, could do much to absorb VOCs. Our main concern with MDF is formaldehyde. It's in the resin that holds the wood fibers together and outgasses for quite some time after the product is installed. My guess is that the best bet in such situations is time...time for the formaldehyde to evaporate (outgas). Unfortunately, people living in the trailers are being exposed this entire period.

Dan
4 years ago
Hi Bob...Here's the answer to this mystery. Clay is hygroscopic. That is, it absorbs moisture. I've been told by others that on a straw bale wall, a clay-based finish (earthen plaster) will draw moisture out of the straw bales, if any enters. As a scientist, I wonder about such things. They make sense, but I don't know if there is scientific proof of such. Dan
4 years ago
Lucas...I've plastered walls (interior walls, that is) with base coat and troweled it smooth, and never applied a finish coat. I like the looks of it, but I worked it with a trowel so it looked pretty. I have also left some walls unfinished...meaning I haven't troweled them smooth. I'm not that keen on the rough look...but that's a personal thing. I built a straw bale cottage at my educational center on our property in Missouri and hand applied the interior finish. It's pretty rough, and looks ugly to me. I am going to offer a workshop this summer to finish it. You can find out about the workshop on my website at www.evergreeninstitute.org. Just click on the schedule...Dan
4 years ago