wofati and earth shelter home floors, ideas and do's and don'ts?

So I have been working on a design for a home to build for my homestead. Getting lots figured out for walls and roof etc. My plan is taking the best of wofati and underground homes as well as some of my own ideas. But the one piece I am struggling to find some good info on so I can make good plans and decisions, is flooring. How to floor my place. I see some stone work and wood flooring in the wofati, but no real deep discussion on how the flooring was done or planned out. Was a moisture barrier laid down, was it insulated, is there an air gap between the wood and earth, did a gravel layer need to be laid down, etc? I really would prefer to avoid concrete for flooring, and like the idea of a mixed stone and wood flooring. I would prefer not to have any rubber, vinyl, or plastic between my feet and the earth.

I have been doing lots of research into underground homes for decades, but for some reason over and over the floors seem to be glossed over and under discussed. But isn't this a pretty important detail. It is the most interfaced surface of the home. You walk on it and touch it constantly. So I am hoping some folks can give me some suggestions and ideas for what to consider for building a floor in an earth sheltered home. Some things that might need to be considered and planned out ahead of time. Any little tricks or hints to make it easier, or to avoid problems.

Thanks in advance for any input into this.

There is an interesting idea for carpet over plastic sheeting over earth in Mike Oehler's  "$50& up" book, that I'm looking forward to trying. Other than that, cob/adobe floors sealed w/ linseed oil are very appealing.

I would like to avoid things like plastic sheeting and carpet under my feat if possible. I am familiar with the technique from Mike's work. It is just one I do not personally like or want.

I have looked a bit into the cob and linseed oil option. Which so far seems like the most probable of choices so far. But I would still like to hear more options.

If you look at the Wofati threads. They have wood floors, what sort of flooring method was done here? Are the boards in direct contact with earth or floating with air between them and ground?

Most wooden floors over soil here just use logs, one side flattened with a saw or axe, then the flooring boards are laid over them and nailed to what we call "sleepers" here in Maine. If you wanted too you could put down some sort of insulation between the flooring boards and the soil, that being sawdust or wool if you want to go 100% natural. Myself I would go wool because I have sheep, but I might treat the wool to stop rodents from enjoying it.

My farm abounds with slate, so if I get around to building one, I want to put slate down on the floor to help soak up the passive solar light and help retain the heat through the night. I have slate in my own house, split from boulders on my farm no less, and it was easy to lay into place. I used concrete between them, but if I get around to building a wofati, I would try screening out bank run gravel so that I was just getting small rocks say 1/2 in size. I say bank run, because crushed gravel from a commercial pit has broken edges that might be sharp, and in our conventional home now we are a shoeless house, and my wife prefers to be barefoot. These 1/2 screened rocks, smooth from being tumbled around by glaciers, could be swept in between the slate flagstones and make a nice heat retaining, flat and natural flooring I would think, but that is just a guess. To get the right size rock between the flagstones, you might have to double screen it. That is dump the bank run gravel over a screen to rid it of the sand and small particles. Then take what went off the screen (as opposed to under it) and dump it over a screen of the size rock you want...say 1/2 inch hardware cloth. What was produced under the screen the second time would be material you could spread between the flagstones.

Now I used slate in my example, but it could be any flat rock. Also you could off "cookies" off a log. I have laid a floor this way as well. I cut 4 inch slices off logs and laid them flat on the ground to make a wooden floor with soil fill in between. You have to remove the bark though first.

My only issue with this might be snakes working their way between the slate or wooden cookies. I live in Maine where we do not have poisonous snakes, but I still am scared to death of them. Fortunately I have ducks...hence no snakes!

An update in the cooper cabin wofati shows the floor cut away to add a rocket cook stove.



You can see the wood is slightly above the ground, and there is a line of nails in what I assume is a wood riser lifting the floor just slightly above the earth. This gives me a fairly good idea of how the floor was put in. Though if anyone involved wishes to add more info on the floor construction, it would be appreciated.

hi Devin, like you i am trying to look into ways to insulate the floor organically and i cannot find much information on the web... One thing i ask myself is do you really need to insulate a floor? Because if warm air rises i wouldnt see how it would leave the house from underneath...I thinking, at least preventing winds from going through the floor by chinking floor boards (for a wooden floor) and also by chinking/closing foundations.

I have read about wool and i think it is a very good idea. I wonder if someone have experience with it and could give more details. I gues you would just have to lay it between floor and subfloor. And also, i remember watching a video of a log cabin construction where floor was being insulated with sawdust. But from looking on the internets i have only found negatives opinions on sawdust...And i wonder if there would be a higher risk of fire?

I know from where im from the old houses use to be insulated in their floors with a layer of news papers (a proper use for that crap) and rags. I just dont think the insulation value of it is very high.

I forgot your question was about underground construction... I had above ground building in mind. Maybe underground you take advantage of the more constant temperatures of the ground so in fact you dont need to insulate from it?

Wool is a really good insulator, obviously natural, warm and something a lot of people do not know...naturally flame retardant. The biggest drawback is that mice like it almost as much as humans, and in this situation, they would be very happy mice. Too happy. That can be compensated for by mixing in borax, which mice do not like, but some people have issues with it.

All this is stated by a sheep farmer who knows wool.

I want to field this question on flooring, insulation, and moisture.....   building a la WOFATI.  I know Oehler's love of earth because it WAS insulating, placed poly/EPDM on top and then (natural fiber) carpet.  

Average AM Precipitation ranges from 3" to 5.25" per month, and humidity from 78% to 88%, and PM from 57% to 68%.

I'm being told, by local - albeit conventional - builders in my area (South Central KY) that I'll need gravel -- lots of it - beneath any floor.  

I resist this with a passion, because then I need a floor, need a moisture barrier (right?), floor (treated? Which i don't want) or wrapped in poly?......  

If I provide adequately for drainage,  as I plan to with the uphill terrace, a curtain drain uphill of that - and the Oehler lowered trough around/outside my main floor level - do I need to have gravel beneath my floor?

Thoughts?  Thank you in advance  -

Robin, I am not sure I am qualified to answer your question, but since it has been a few days and no one has helped you, I will try.

I think you need gravel, but not that much and maybe not for the other other building materials you mention; treated wood and poly.

It seems as if you have a really humid area for sure, so to that end it would seem to me that having gravel is a requirement. Not so much for drainage as to just break the capillary action that might draw moisture up into your floor. In other words a few inches. I see nothing wrong with this ethically if you could find some on your land or barter for some. It need not be quarried, crushed and sized. A simple A frame and hardware cloth will give you the size rocks you need with nothing more than a shovel, wheel barrow, (or 5 gallon buckets) and a car.

(I once moved some 3 cubic yards of sand for my home with a shovel, a plastic children's sled, (3) 5 gallon buckets and a Ford Focus in the dead of a Maine winter).

As for a floor, even if you wanted wood, you need not go with treated wood. I am not sure what you have for trees, but here in Maine we have Cedar which is very rot resistant. No treatment needed. I have successfully used rock taken for my land to make a floor, and do not be overly concerned if it is not consistently thick. It takes extra work, but you can dig out earth under the rock and get the one flat side a rock has to make a VERY smooth floor. Home Contractors hate this because time is money, and so they need consistency to speed things up. To get that consistency though in building material like stone, requires a lot of money. As home builders working on our own places, that is where we have a lot of latitude.

Here in Maine...gasp...we do not use a lot of poly or vapor barrier. In the 1970's government agencies giving loans required it and by the 1980's the houses were being rebuilt because they were rotting out. I would think a house, even a WOFATI...if properly situated would allow enough air flow so that moisture is wicked away. A little gravel under your floor to help break capillary action...yeah I can see that, and by a little I am thinking like 2 inches or so.

One thing I have learned over the years is this; no matter what is proposed, 15 people will say your idea cannot be done; no way, no how, no possibility. Now they have no real solution themselves that is creative, just that yours sucks. So from there a creative builder has to ask this; what is the worst scenario? There is a chance that you might have to eat crow and say "hey, they were right, I did need lots or gravel, poly, and treated wood...but you just might have a house that you wanted for the next 40 years too. Myself, my house is constantly evolving, constantly getting better because I always work to make it more functional. I have 4 daughters...I have too! But some people cannot rip something out they installed. I can. Considering most houses change in style every 10 years, I do not look at any job I do as being a forever thing. If you are the kind of person that wants it done right, the first time, forever...maybe doing it as your contracting neighbors say is best. But if you are a bit like me, doing something as you want may make more sense.

If it helps, I think I have come up with more creative solutions then I have had to eat crow...

Travis,

This absolutely helps and thanks for being brave enough to answer.  Like another poster, I am feeling a bit hurried to get this enclosed before it gets cold here.  With that pressure, I have already accepted cutting some corners that would normally be totally natural, land- and earth-sourced...  I have little experience building and YES, have been told "it's not done here", "sure, up NORTH"...   Since I first dug my uphill patio, (which promptly collected water), I have researched and changed the plan.  Like Paul's WOFATI, where he suggests (in the drawing at least) the uphill should be lower than the home, I intend to raise the home level off the original (totally UG) home plan.  But, in keeping with Oehler's MORE underground, I want to keep it incognito more than a mound of dirt. At the risk of offending, (please, it's not on purpose, but of ignorance), is Paul's dislike of the word "underground" due to perceived negative?  I have been grounding a while and LOVE the idea of a GROUNDED home...  solid, good air, etc.  I will compromise.

What would you think of a double-layer on the floor, i.e. two layers of poly or moisture barrier on the FLOOR  - with soil in between, like the top of the house -   to keep seepage/humidity/moisture out?  What would you suggest to segregate the gravel layer from what's above it?  I can only think of plywood, because of the size/level surface.  If I revert my plans back to timbers from the property, curing and debarking time is involved. I could mill some trees into wider boards over poly/barrier.

Thanks again!  Time permitting, if you want, feel free to PM me.