Wofati/Oehler/PAHS on bedrock?

My land seems to have a high water table and shallow bedrock. It looks like my only option for earth-sheltering is to build on grade and raise the grade up and over the home. I've found an outcrop of raised bedrock that has enough square footage for a modest home but I'm not sure how I could attach the structure to the bedrock. What if I poured a footing with lots of anchors drilled into the rock and somehow attached posts to the footing? Could this arrangement resist the lateral forces of all that earthen cover? With a PAHS-type approach to insulating a large umbrella over the whole thing could I reasonably expect the bedrock to be tolerable on the feet at -45deg? As I said, the bedrock only pops up in a small area (that would be enclosed by the structure) and drops off around the perimeter. In theory, when completely backfilled the bedrock would be under at least 5 feet of earth plus insulation on the south side and 10 feet plus insulation on the north, east and west. I realize this endeavour may seem illogical but that's the kind of stuff I like to pursue.

I think you could indeed drill and anchor bolts into the bedrock, and a friend of mine I respect mentioned a particular stone adhesive that he says is incredibly strong, or concrete or some other bonding agent.

Or perhaps you could use a rock hammer to create holes in the ground to sink the posts and backfill with tamped gravel? It wouldn't have any drainage if you did that but all the posts would be well covered all around by the umbrella.

Either way that would take a looooot of fill dirt to fill the umbrella and then cover it up.

--Joshua

Hi Mike S., et al,

I am not sure how much of what I have written here at Permies.com you have read. Some of it is germane to your goals. I have covered everything from "Raised Earth Foundations" and will soon release one called "Earth Lodges and Other Fossorial Architecture."

Being a Permaculture Forum and focus mainly on "natural and traditional" building, we try to focus as much as we can on only natural, recycled, and/or sustainable building practices in means, methods and materials. OPC (ordinary portland cement) based products are neither natural nor sustainable materials and the industries behind the are some of the largest polluters in the world. Because I design and build professionally I am forced to use this hideous material way more often than I would like. 90% of the time it is completely unnecessary and only adds a miss perceive notion of speed. I would further point out that it is a common mistake for folks to think that OPC is a "glue or adhesive" of any kind...it isn't...and by PE (professional engineer) standards will not meet that criteria.

Without photos of the project site, professionally it is difficult to give any valued advice other than to state that this is a common vernacular building style in many culture through the ages. I do have some concerns with Radon Gas entrapment in such a structure but that can be mitigated if Radon is found to be present.

Will it be warm enough?

Yes, in most cases it will be warm enough as the the earth has a much warm ambiance than the surrounding biome climate. If you note, many spots like yours with shallow bed rock often have exposed stone even in winter...This is because of the "interstitial heat" that the mantels of the planet generate.

Footings?

There is several traditional footings that can be employed, yet lets get some photos up before I ramble on about those. If you go through my post you should find several photos of stone plinths for wood post that have been carved into bed rock for a timber frame...much like you are wishing to do. Carving into the stone is the second most common form of foundation for this type of architecture, while just setting a timber frame armature of wood is the first.

Look forward to some photos...

Regards,

j

Hi Jay,

I don't know if this photo will give you any better idea of what I'm dealing with. The maximum dimensions of the exposure are about 65' (vertical in the photo) by 25' (horizontal in photo). The high point in the center is about 2-3' higher than the edges where soil meets rock.

Yes, I've followed a lot of your posts but may not be completely comprehending some of the stuff you discuss.

Thanks,

Mike

Joshua Chambers wrote: Or perhaps you could use a rock hammer to create holes in the ground to sink the posts and backfill with tamped gravel? It wouldn't have any drainage if you did that but all the posts would be well covered all around by the umbrella.

Either way that would take a looooot of fill dirt to fill the umbrella and then cover it up.

Thanks Joshua,

I don't think the rock would be easy to hammer into. It's several-billion year old metasediments, as far as I know. Regardless, I do agree that backfilling the umbrella might be a monumental undertaking.

Thanks for nudging my thread out of hibernation,

Mike

Mike......I am so sorry that I did not see your post earlier (criminy...July...I am a real "Dolt" sometimes!)...Thanks...big time...to Joshua for bringing it to our attention!!..

I can get a much better feel for the building site now...thanks for the photo!

Hmmm...looks like some pretty nice...?...lime stone?

If so is it Oolitic limestone or some other variety?

I see what you mean by shallow soil depth...WOW...that looks sparc, but I bet the water quality is great!

As for a wofati of some other earth style build...this may be more of a challenge than it is worth...(not sure yet)?? It will depend on the soil types present that you can mound up...We need clay soils with no organic material...

Positive aspect you already have a great million plus year old foundation to build off of...!!...

So....

Is there clay on the building site in the amounts to properly cover the size structure this project is calling for?

What other natural/traditional building systems have you considered?

What is the traditional vernacular architecture of the region?

What type of standing timber do you have?

What is its quality?

How much land do you have at your disposal to build with and from?

Will you be doing this yourself?

Is there any heavy equipment available?

Is Radon and issue in the area?

That should help me (all our readers) understand a bit more of your goals and what can be effectively facilitated...

Regards,

j

Hi Jay,

No need to apologize. You seem pretty darned busy on this forum and it doesn't surprise me that you might miss one or two topics.

"Hmmm...looks like some pretty nice...?...lime stone?" - No, it's a very old pressure cooked reiteration of various billion-plus year old sedimentary rocks.

"I see what you mean by shallow soil depth...WOW...that looks sparc, but I bet the water quality is great!" - I hope so, but my neighbour tells me the water is hard.

"As for a wofati of some other earth style build...this may be more of a challenge than it is worth...(not sure yet)??" - Yes, you're probably right. I'm investigating other locations on the property that may be better suited.

"Is there clay on the building site in the amounts to properly cover the size structure this project is calling for?" - There is a lot of nearly pure clay just beneath the humus. That is causing the high/perched water table.

"What other natural/traditional building systems have you considered?" - For simplicity and expediency, we are considering a yurt to get ourselves settled onsite and unencumbered by our home in town (to be sold).

"What is the traditional vernacular architecture of the region?" - A lot of the 'original' homes here arrived by train and were assembled on posts or cribbing. Some of them actually have hinges where the panels unfolded and sprung into shape. Not a very good template for my purposes.

"What type of standing timber do you have?" - Much scraggly black spruce and poplar, with some nice large (8-16") Tamaracks.

"How much land do you have at your disposal to build with and from?" - 26 acres, of which almost half is inaccessible without good rubber boots. The land slopes very gently toward a bog, and during wet months the bog endeavours to expand its empire.

"Will you be doing this yourself?" - My genetics dictate that I stubbornly refuse any help that may expose my ineptitude.

"Is there any heavy equipment available?" - A compact tractor with loader and a large tractor with backhoe attachment.

"Is Radon and issue in the area?" - I can't find any mention of it but have only scoured the web thus far.

I should explain also that we intend to remain untethered to the grid and this entails heating a home with wood. I don't like the idea of annually raping the forest for my comfort, so I want to do as much as possible to limit our heating needs. We are not unwilling to sacrifice extravagance for simplicity and efficiency.

Again, I thank you for your time and effort,

Mike

(Note: some words have links to them...take a look...)

Hi Mike,

lime stone?" - No, it's a very old pressure cooked reiteration of various billion-plus year old sedimentary rocks.

Eraah......Mike...Limestone is a sedimentary rock... If it has actually been "pressure cooked" that would make it a metamorphic...and...if the parent rock was limestone then the result 'chrono-chemically' "cooking" it into well...Marble...It's not marble...is it? OR, do you have Quartzite slabbing formation in the area?

Beside Rockhound, Mountain/Rock Climbing AMGA Guide, and general...nutt...about stone, I also quarry and carve stone. Its really hard sometimes (especially with lighter color stone) to tell species by just a photo. Knowing the exact stone species will tell me (as a stone carver) what type and fashion of tooling and work the stone will take and need. See if you can find out for us... It helps in understanding a great deal about the biome also...

I hope so, but my neighbour tells me the water is hard.

Hmmm...well, there is another hint to stone species...limestone facilitates "hard water" (from hard to form sudds with soap.) Hard water usually increases the ph of your soil. Hard water contains calcium carbonate and magnesium carbonate, same chemicals found in limestone. Limestone is often used in small amounts to raise the pH of your garden, and hard water can do the same thing. Hard water effects on gardening are dependant on other factors like soil type, but usually reduces the control we have over the soil acidity, which is a drawback in ease of gardening, but the water itself may not always be bad for the garden. If you live in an area with acid soil, for example, your garden may require limestone to decrease the acidity. Having hard water will just decease the amount you need to add. If your hard water makes your soil too alkaline, it will harm acid-loving botanicals. You may be able to balance the alkalinity by adding soil acidifiers. Alternately, you can chose plants that thrive in the high-pH conditions.

All in all...we need to know the stone and the water quality including PH.

For simplicity and expediency, we are considering a yurt to get ourselves settled onsite and unencumbered by our home in town (to be sold).

Yurts and Gerr and ....

These are all great! I have built several traditional ones and own a 16' one. Great way to get onto land and live there quick. They can be quite comfortable and easy to facilitate...

A lot of the 'original' homes here arrived by train and were assembled on posts or cribbing. Some of them actually have hinges where the panels unfolded and sprung into shape. Not a very good template for my purposes.

Ya...Er...I was thinking more like going back before trains...perhaps to pre European settlement or just after? I do believe I have contacts in your area that still find traditional French/First Nation's "Piece sur Piece" (a.k.a "Post and plank" timber frames) These are often made from Tamarack and have a 1000 year old history in many forms where there are boreal forests. Just a thought I would offer...

My genetics dictate that I stubbornly refuse any help that may expose my ineptitude.

Ha..Ha..ha......I would suggest some "gene splicing" or DNA re-sequencing to achieve the ability to ignore worries about ineptitude...I am glad you want to do this yourselves...Good for you!...

A compact tractor with loader and a large tractor with backhoe attachment.

Excellent...this will save the need for slave labor, indentured servants, and/or waiting for kids to get big enough to put out to work... Plus you will save your back and get more done faster...

Wood heat can be very sustainable if facilitated correctly with the correct balance of "wood burning" device and super insulated traditional/natural architecture...

We are here to help...

Hi Jay,

The geological mapping here is not as detailed as in the U.S., so I can't establish anything more specific than 'metasedimentary' for my bedrock. It may have been sandstone, limestone, mudstone, siltstone, etc but it's been cooked and contorted well beyond recognition and is not a candidate for cleaving.

Based on indicator plants, I'm thinking my soil ph is more on the acidic side (blueberries, Labrador Tea, black spruce,etc). I'm not sure if the 'hard water' terminology my neighbour used was technically correct but they were emphatic about their whites coming out of the laundry process looking non-white.

Partly what I find appealing in the Wofati/Oehler style of construction is the drastically reduced exposure of the structure and the resulting protection from the elements. I replaced the shingles on my roof a year ago and made note of the absurdity of placing several thousand dollars worth of material in the direct path of the sun, snow and rain and knowing full well that the clock is ticking the moment it's installed. Having a roof that is self-regenerating soil and plant matter seems so much more sensible.

So, how do you feel about earthbags? Owen Geiger seems to think it's a perfect match for my ineptitude. I'm thinking that a combination of Oehler, Wofati and earthbag could produce something reasonably natural, durable, efficient and frugal.

Mike

Hi Mike,

It may have been sandstone, limestone, mudstone, siltstone, etc but it's been cooked and contorted well beyond recognition and is not a candidate for cleaving.

Well, if you ever get a good identification from say a regional Provence geologist...it would be great to know. All stone split and cleave so that won't really be and issues some do so better than others, most do better if you know the species...

It does sound like the water may be hard...Time will tell...

So, how do you feel about earthbags? Owen Geiger seems to think it's a perfect match for my ineptitude.

Well...I have studied well this modality of earth building, visited several, studied hundreds and built several small and/or models. General view..."the jury is out?" This is just too new a method to really tell how long a life span the architecture will have. I suspect some a very long time while many...not so much...

General rule of "good practice" in architecture...look to the vernacular systems and/or resource available. Don't..."try"...to make something work when other more germane and pragmatic, "means, methods and materials," are available.

I believe you can "try" and make EB methods work...and perhaps even really well? Less work than others...I would guess not. More sustainable and longer lived than others...I would guess the same...maybe better? under some conditions. Put the correct roof on any structure and it should last someplace between 150 and 1000 years...all depends on modality.

Canadian Dirtbags would be a good read and may stimulate more thinking and dreaming of this path...

Let me know if I can be of further assistance and help hash through any thoughts...

j