Fibercrete Plaster

[glenn-k]

I tried plastering with a fibercrete mix today.  It is a stabilized earth plaster made from local mineral clay 10 parts, sawdust 10 parts, lime putty 2 parts, cement 1 part, asphalt emulsion 1 part.   It was applied over jute erosion control netting on top of 30 lb roofing felt.   I am using this to seal a roof extension over a sloping straw bale wall.  On the straw bales it looks like I will be able to apply it directly.

 It is very easy to work with and very sticky- it will even stick to the felt with no jute over it.  It is experimental and I will monitor how it takes weather.  It will have a board to protect the top only.  The sides will be exposed directly to the weather.  The asphalt should waterproof it.  This is a similar formula to some mentioned in Ken Kerns books and is a variation of current information from Taylor Publishing.

[admin]

Most interesting Glenn,

I'm glad you are able to test this type of thing and report back. Things up here are already too wet for any such experiments. This is the land of cedar (and the cedar ends up with a final coat of mildew or some other small plant organism).

However, when I was in the Peace Corps in Iran, we did some experiments with asphalt stabilized adobe blocks. They held up much better in the Kurdish region where I was and which got more rain and snow that the lowlands. It was a very cheap product there as it was a by-product of oil refining.

John

[glenn-k]

For anyone interested in playing with this stuff the asphalt emulsion is available at most lumberyards as Henry's # 107 or Blackjack is another brand.  I read at a stabilized adobe brick website that they used only 4% in their clay.  It is under $20 for 5 gallons that way but the adobe site used CSS1 which is a road sealer and the last time I bought it it cost about $.80 per gallon (yes 80 cents).   That was a couple years ago.

We have had winter weather here for a couple weeks but it is nice now.  My clay pit had enough water in it to dig it with a shovel - of course I had loosened it with a backhoe last year.

My wife did most of the digging and mixing -I did most of the plastering but got the first coat finished then mixed some concrete bonder with some of it and put a fresh coat over the earth plastered strawbales from last year that are around the fish pond on the roof.  They were covered with a cob and sand, AE plaster last year and did survive the winter -25 inches of rain total.  We had a little too much sand last year but it did work - This year we are not adding sand.  Maintenance for the year took 2 people about 1/2 hour- .

Things that are made from earth that are covered such as my clay oven, frog etc. are pretty maintenance free - just a fresh concrete cure and seal coat to make it shine once in a while.

[jraabe]

Glenn:

Have you seen this video and do you think it would be helpful to folks?

http://www.dirtcheapbuilder.com/intofibwitmi.html

[glenn-k]

I haven't seen this video, but anything Charmaine Taylor recommends on the Dirt Cheap Builder site is good information as she is a real alternative building experimenter herself.  

[jraabe]

I added her link page to the referral section of the forum. There is lots of information there.

[timby]

I found a web site that has a concrete product that looks very interesting

http://www.structuresusa.com/applications.html

Low cost, easy to use, and affordable.

Take a look.

Later

[glenn-k]

Well now - it is over 2 years later and the above formula was a bit weak.   It has not totally given up the ghost, but it is time to re-plaster it..

I have noticed something about the clay here -- It removes any tar from tarpaper - maybe asphalt emulsion from the mix too? in about 2 to 3 years.  Some 30# felt I put underground to protect plastic membranes from rocks 4 years ago is now felt with nearly no asphalt in it - just hard brittle black paper.  It's still doing its job - just not as water repellent.

We had a similar experience with the two strawbales on the roof for seats.  AE mix in the plaster was good for a while then a crack here - a crack there and the bales got a bit of moisture - that was the end for them.  Looks like a solid roof over bales is one of the only dependable ways to keep it.  I read of failures in strawbale fences later also.  Too hard to keep them dry without a roof of sorts.

[desdawg]

Glenn, in the fibercrete "recipe" you used sawdust. Is this presoaked sawdust to increase the drying time and reduce cracking from drying too quickly? Or did you have another purpose.

[jwv]

Glenn,

Do you think a lack of breathability had anything to do with the failure?  I would think if it was on a roof (?I may have misread?) any moisture that made its way to the tarpaper would just sit there. But that would also be true of a vertical surface. Also, lime is a somewhat finicky material. At least, in my limited experience. I wanto work with it more.

With a decent overhang and wouldn't unstabilized earthen plaster work?

I have also used sawdust in a few mixes and like the way it goes on-smoother as compared to even the finest screen straw.

As for weatherproofing, I have ordered some PrimSil (potassium silicate) http://www.eco-house.com/PrimaSil1050.htm for the west wall of the house.  Here in the desert we don't get a lot of rain but when we do it's usually sideways and alot in a short time. I've done some relief work on this wall and don't want it to wash away with the first monsoon rain! I'll let you know how that works.



Judy

[Sassy]

Judy, the mixture with the sawdust was a nice medium to work with, but on the wall we put it on, over the Hessian mesh, did not hold up out in the weather - gradually disintegrated...  :-/  Glenn says it would probably hold up well if it was not exposed to moisture.  

Your wall looks nice!   I'm going to have to take a look at your blog again.

[glenn-k]

I went out and took some pictures for you, Judy.

Here's what I've got.

Glenn,

Do you think a lack of breathability had anything to do with the failure?  I would think if it was on a roof (?I may have misread?) any moisture that made its way to the tarpaper would just sit there. But that would also be true of a vertical surface. Also, lime is a somewhat finicky material. At least, in my limited experience. I wanto work with it more.

I think it would have held up better with a roof.  I think it was still plenty breathable and that was part of its problem.  Even concrete or stucco will take in moisture unless well sealed.  Many of the old plasters used cactus juice - casein or something else mixed in  as a waterproofer.  I used some AE in this formula - maybe not enough but I think there was enough sawdust and clay bits exposed to shrink and swell to break this plaster up - made worse by my failure to get a roof over it.  This picture shows the angle pretty well and the remaining plaster.  The roof I was going to put was only a cap and I think the plaster would still have failed.  The green bits you see are small chunks of claystone which I left as part of the aggregate.  It is water resistant.  I think a few pieces of sawdust exposed, repeatedly shrinking and swelling help cause the breakup of this plaster.  I think a mix like this is great for inside plastering - as you said - nice texture - much lighter, somewhat insulating  and nice to work with.



Here is one that has held up - totally exposed in areas with no roof to the left and only partial to the right - top is under a few inches of overhang.

Underground Cabin Update - More Durable Mix
Reply #15 - Feb 3rd, 2005, 8:20am Currently I am covering the front section east wall with  stabilized earth plaster - 10 sand, 4 clay, 2 lime, 1 cement, 1/2 fast set cement, 2 handfuls cut straw over stucco lath.  This is an infill wall over a post and beam log frame with a window framed in it.  This method allows me to take the sidewall covering completely to the top over the earth retainer boards and over the exposed edge of the plastic on the roof.  The wall look will be of adobe pueblo style where it rises above the excavated earth.

Compare the Durable Mix above in the picture below with this Sawdust mix- key change is the sand in the durable mix.

Fibercrete Plaster Oct 30th, 2004, 11:46pm
I tried plastering with a fibercrete mix today.  It is a stabilized earth plaster made from local mineral clay 10 parts, sawdust 10 parts, lime putty 2 parts, cement 1 part, asphalt emulsion 1 part

Remember that it is quite common for the family or community to get together annually to completely re-plaster earth plaster buildings.  This is often what keeps them up rather than being impervious to weather.  

More info for you -- Here is some of my better made cob - totally un-stabilized with a 3' overhang 10 feet above- totally exposed to south west storms and driving rain.  Here I had a good mix of 30% clay 70% sand/aggregate (working out to about 50/50 considering clay aggregates as dug) and straw.  I would say only the surface 1/8 inch or so is gone.  Good roof over the top -rain to probably 6 feet up the wall and an average of 25 to 50 inches per year for about the last 4 years.



Now the bench inside the conversation pit area.  Tree roots have grown through a couple areas of the back doing very little damage and repairable in less than 10 minutes.  My point here is that water has come in these holes and stood on top the un-stabilized bench that has had Quickcrete Concrete Cure and Seal applied to the surface.  The wet areas even though under standing water for several weeks do not get wet underneath.  This also may be a good sealer for walls that only get sideways rain.  The water from underground behind the bench softens the cob so the roots can grow but does not deteriorate it.



I am interested in how the potassium silicate works - I think it is also one of the things usable as a fire deterrent for wood similar to sodium silicate.

[jwv]

You do get a LOT of rain- and with a roof your wall probably would have been fine. Then there's just the factor of lots of driving rain.  Once it finds a way into something whether it be earthen or cement stucco, you're done.   It's just that the earthen is easier to repair.  You're so right that repair of adobe walls was a part of the yearly community activities.  The great San Xavier Mission here was almost destroyed once they started repairing it with cement stucco.  Eventually went back to nopalito juice.  I've never used cactus but have used wheat paste-both commercial and home made and casein in the form of dried milk powder. WE used wheat paste for the plaster of the exterior of the house and will use it inside.

I'm now contemplating a cob wall at our place.  We're right on the walking path and our south patio woud be on display 24/7.  Even tho I like to be sociable would like to have a low wall along the south west for when I don't want to be sociable.  The path is actually about 2 ft lower than the lot so my wall only has to be about 4 ft.  I'm thinking that I want to do a rock foundation (we have plenty!) with cob and perhaps bamboo.  Picture 4ft section of cob then 4 ft section of bamboo, section cob, section bamboo etc.  Will than cap it with probably galvanized-maybe flashing bent to cover-still in the planning stage.  I'd put a bench on our side of the wall and maybe a little fireplace.  Make a nice outdoor room.

Here's an interesting album on the plastering of the Tower Gallery at Poajoque, NM.  http://caneloproject.com/images%20cp/currntprojects/gallery/index.htm

Anyone who's driven Albq to Santa Fe has seen this interesting building.  It sat empty for years but is now being put to use.

Judy

[desdawg]

Judy, that wall is beautiful. I really like it.

[glenn-k]

Sounds like a good plan, Judy.  Nice pics in the gallery.

Our rain nearly all happens in about 4 to 5 months.

[Sassy]

Thanks for the link - really enjoyed looking at those pictures - lots of good ideas for when we finish the "deep part/great room"   .

Also enjoyed browsing through your blog again - great job!