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After 6 years of living in cob, my list of what I'd wished I'd done different. additions?  RSS feed

 
Tys Sniffen
Posts: 54
Location: Northern California
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I've meant to start this list for a while, and I'm sure things will continue to come up, but I thought perhaps you folks who are just starting out might find a few of these hints helpful.  Perhaps others would add to the list.

- I would put granite pieces as bottom floor for all niches.  I can’t believe I didn’t see the problems of lime wash plaster being horizontal
o collects dust and can’t really be cleaned
o easily chipped by things being put on the shelf
this should probably also apply for all cobbed in windows too.  In cob books, you always see all these whimsical niches that are completely plastered. You never see the photos of those niches years later after the dust and dirt and wear have messed those niches up.

- No exposed edges/curved walls where traffic and kids would bump into them and chip them off

- I’d do a vertical tile border around all rooms where the floor meets the wall.  Again just to protect the plaster and make cleaning easier.

- I did 6 coats of linseed oil on my earth floor, all the same day, waiting for one to soak in before adding the next (not the other way, of waiting days for it to harden, then do another)  After 5 years, my floor is still not hard enough.  You can’t sit on a wooden chair straight on the earth floor without it leaving dents. 

- diatomaceous earth!   I wish I’d known about this stuff during the building process.  Out here in the woods, we get ants trying to come in for water and food, every summer.  We did the best job possible of making our house critter-proof, but ants can find a knife-blade edge space and get in.  There are MANY places that, had I had the fore-sight about the wonders of diatomaceous earth to keep bugs out of stuff, I would have built it in.
o Under kitchen cabinets, behind the kick plate, where there’s a space between the bottom shelf and the floor
o Between vertical wall pieces (I have a wooden wall inside my cob house that has sandwiched plywood and veneer and such. I know ants are in between those sheets.  I would have dusted between each one.
o Up in the roof – in the soffets and in around vents (and I have 2 sets of bug screen already in place!)
o Inside the french drain!  Spread over the gravel in the trench under the walls!
o Probably other places I can’t even remember anymore

and while it wasn't feasible at the time, and probably generally isn't for anyone, if I could somehow choose my schedule, I would have done the rough cob walls on top of my stem wall and then given them a year (or two!) to settle before doing the rest of the plaster and internal work.  Even though we planned quite well and did good work on our stem wall, the slight settling of the house has created a few small cracks in my finished plaster in some of the few weaker spots up towards the roof.
 
Giselle Burningham
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Location: Australia, Now zone 10a, costal, sandy, windy and temperate.
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This is really interesting, a huge eye opener on a number of levels. Ants... It's Obvious now you point it out! But it didn't even cross my mind.  Thank you.
 
Rebecca Norman
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Useful post! I've lived in something similar to a cob house for 20 years and can add my observations. At our school, my living section is adobe with earth plaster, and the big school building is old-style rammed earth (could also be called form-worked cob) with earth plaster.

Tys Sniffen wrote:
- I would put granite pieces as bottom floor for all niches.  I can’t believe I didn’t see the problems of lime wash plaster being horizontal
o collects dust and can’t really be cleaned
o easily chipped by things being put on the shelf
this should probably also apply for all cobbed in windows too.  In cob books, you always see all these whimsical niches that are completely plastered. You never see the photos of those niches years later after the dust and dirt and wear have messed those niches up.


I agree! A flat wooden board or a slate bottom in shelves and niches would have been better.

Tys Sniffen wrote:
- No exposed edges/curved walls where traffic and kids would bump into them and chip them off.


I'm not sure what you mean by exposed edges and curved walls. In our experience, curved corners are much more resistant to chipping with kids running around and moving furniture, than sharp corners. I'm talking about places like the edges of doors, and anywhere that the corner of a wall is sticking out. In some places we've decided to chip off the whole sharp corner and replaster it with a soft curve because of this problem.

Tys Sniffen wrote:
- I’d do a vertical tile border around all rooms where the floor meets the wall.  Again just to protect the plaster and make cleaning easier.


Do you mean a horizontal border? That would make some sense. We have a little wooden baseboard along the bottom of the wall in many rooms, and it serves that purpose.

Tys Sniffen wrote:
- I did 6 coats of linseed oil on my earth floor, all the same day, waiting for one to soak in before adding the next (not the other way, of waiting days for it to harden, then do another)  After 5 years, my floor is still not hard enough.  You can’t sit on a wooden chair straight on the earth floor without it leaving dents. 


In high traffic rooms we have put in either wooden flooring or slate flooring. In low traffic rooms like some bedrooms, we kept the earth floor but covered it with a mat. We haven't tried to use hard packed earth as flooring in anyplace that would have high traffic or chairs. I've seen it done, by a guy named Brian Woodward and his wife, in Australia. They had gorgeous adobe floors; with a dining table and chairs, and everything. Sally was redoing some patches of floor while we were there: it seemed to involve repeated lengthy rubbing down and linseed oil or something; mainly I remember her talking about rubbing it down hard, again and again. We tested out a linseed surface on the doorstep of our little house; several layers of linseed oil with time to dry in between. It's been several years now, and still in good shape, only one chip and it's not really growing. It's not a very high traffic place because only one or two people use the space, but it is the doorstep so it gets wet occasionally and gets stepped on several times a day. It is also exposed to extreme sun. Personally I'd go with wood or stone or mats if there's going to be a table and chairs, or high traffic.

About the last point, I haven't had a problem with ants, so I can't say anything to that. I don't feel that's a problem special to cob, but just a problem that can really happen in any house regardless of material. I hope you find a method for dealing with them.
 
Tys Sniffen
Posts: 54
Location: Northern California
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tile border - yes, it goes horizontally along the wall/floor.  I think of it as vertical, because the tiles create that *vertical* 90 degree turn from the floor.    it's very common in traditional Latino/south American building.

about the curved edges: yes, some really nice, fat curves work well, but there's just bunches of little spots where I guess the curve is just not obtuse enough...  or it's a high traffic sort of spot.  

we did a lot of research on the floor thing, and were told that our 6 coat process would stand up.  it doesn't quite make the grade.  we have tiles by each door, so wet shoes and high traffic are dealt with there.

I'm interested to hear other people's thoughts... or even questions from planners.
 
Ardilla Esch
Posts: 225
Location: Northern New Mexico, Zone 5b
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I agree with much of what you said.  A lessons learned post is a great idea BTW.

The bullnosed plaster in doorways is fine in some places, but I do regret doing it in a couple doorways that get dinged.  Also, I should have used mesh reinforcing of the larger bullnosed corners when plastering.  The only cracks in the plaster are on a few bullnosed corners.

I regret not putting baseboards in more rooms given the earth plastered walls.  Also, I had better results installing baseboards between the scratch coat of plaster and the color coat rather than after the color coat.  Gaps are inevitable when installing base boards to walls that aren't perfectly straight.  Installing them before the color coat allows the plaster to cover the gaps.

I put stone in the base of niches, benches and window frames - definitely a good idea.  In the kitchen windows, I wish I'd used deeper pieces of stone.  The edge of the stone in the windows doesn't quite overlap the backsplash of the counters.

On the earthen floor, I put a wood floor finish (Bioshield Hard Oil #9) on top of the fully cured linseed oil treatments.  That really helps the durability of the floor (and it looks good).  You may consider doing that.

There was a big ant mound in the center of the house before we built.  I dug it up with a backhoe and mixed in Borax.  Also, I dusted the ground heavily with borax before building up the earthen floor.  After a few years we haven't seen any sign of ants under the floor or foundation - just the normal few that march through gaps in weatherstripping.
 
Tys Sniffen
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Location: Northern California
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Ardilla Esch wrote:
On the earthen floor, I put a wood floor finish (Bioshield Hard Oil #9) on top of the fully cured linseed oil treatments.  That really helps the durability of the floor (and it looks good).  You may consider doing that.


We waxed with bioshield beeswax mix... do you think this could be put down on top of that?

and what's the process? that is, how long does it take to dry, how stinky is it? can I put it on one part of the floor and live in the house at the same time?
 
Ardilla Esch
Posts: 225
Location: Northern New Mexico, Zone 5b
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Tys Sniffen wrote:do you think this could be put down on top of that?

and what's the process? that is, how long does it take to dry, how stinky is it? can I put it on one part of the floor and live in the house at the same time?


No, you would have to strip the wax.  At least you should get as much off as you could.

The hard oil is applied by brush and allowed to dry for at least a day.  I would give it more than a day if possible.  It isn't too stinky - at least I don't remember it stinking...
 
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