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Kris Arbanas
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Location: PNW
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I am looking for help/suggestions on a foundation that I am looking to do. I recently took over a property with a 10 year old concrete pad. It was originally destined to be a timber frame home but he never went through with it. It isn't a slab on grade as it is sunken 2-3 feet from surrounding land. From what I understand, it would have been the bottom of his crawl space. The foundation isn't really usable for another plan as it is compromised in some areas and the footings are in unique spots.

It is the ideal and only reasonable spot for our future home and we have decided on a log home plan. Our footprint is quite a bit smaller than this one. I had the idea of filling and then putting a slab on grade over it but the fill required, if brought in, would be quite expensive. Alternately I thought of pushing some fill in from my own land, compacting then pouring the slab. I want a slab on grade because we designed passive solar and I want the thermal mass of the floor.

Any thoughts or suggestions of what could be done?
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Jay C. White Cloud
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Kris Arbanas wrote:I want a slab on grade because we designed passive solar and I want the thermal mass of the floor.

Any thoughts or suggestions of what could be done?


Hello Kris,

If I may suggest, at least for me, the prospects of "I want a slab" kind of narrows done the options for "any thoughts or suggestions," as opc slabs are anything but..."natural building." If this is the path determined best fills the project needs (and it is a very common path for many today) than there maybe a broader spectrum of germane advice found on more "main stream" building forums...if this hasn't been looked at already. Placing this in the "passive solar" forum as well will solicit all types of feedback and advice.

I would perhaps hope that reading some of my posts on foundations may, at minimum, give some different insights , or at least outline some of the more enduring and longer understood methods than many of these modern opc based methods that haven't proven overly superior in anyway to the vernacular. Additionally, having readers understanding the "point loads" and actual project layout is rather important in giving/getting good advice or recommendations for a give design. Overall, it looks like an interesting and potentially exciting building project.

Regards,

j
 
Terry Ruth
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Besides what Jay wrote it is not a good idea to put a slab at some fill depth above a slab. OPC causes all kinds of drying issues unless it is managed, having a slab below a slab won't allow for capillary drainage of the upper slab and moisture will not be allowed to breath, nor dry in either slab since I'm guessing plastic sheet under the existing slab to make matters even worse. Not a good idea to bury flat concrete below grade. Also, if you don't understand your core "fill" soil, if that is what you are using, you could create a expansion chamber bounded by two 4-6 inch concrete skins as a floor, not good. Even if you use a stone new sub-slab core over the old slab you still have no drainage path. Your only hope would be lateral drain tiles if you could slope min of 1" per foot and get them to drain.

The best choice is to get a jack hammer and skid loader haul it out of the way start over. If stuck on concrete use a natural one. If that cost too much I use 9/16 MAG Board as a slab finish floor it handles OPC slabs well. Cost about what plywood does shipped and you don't need a finish floor. It is excellent not just thermal but hygroscopic mass what most commercial mixes fail at, and a thermal break. Do find out how much OPC, flyash, MGO, lime, harsh chemicals additives are in the ready mix...shop around you want a pure inert mix. Get footing dimensions from the foundation chapter 4 in code, size up code min if you can afford it. Create a good site pad and at least 24" overhangs.

Premier makes a light burn MGO ad mix that drastically improves the mechanical and physical properties of most OPC dropping the need for OPC if one can get the ready mix company to add it. We should support Premiers efforts to bring MGO mining to America.
 
Kris Arbanas
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Location: PNW
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I know concrete isn't the ideal material for building as natural as possible but I don't see an engineer signing off on something else. Drainage is definitely a concern of mine. I figured if I drilled enough holes in the existing, it would allow proper drainage. Maybe that's wishful thinking.

I was going to use Mag board for the walls but didn't consider it for the floor. Sounds like an option.

What are the issues with flyash, MGO, lime in the mix. Heavy metal content? off gassing?
 
Terry Ruth
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We been building out of concrete for centuries and it is a natural way of building. There are some that do not like what OPC does to the atmosphere since it gets burnt at high temps, produces CO2, etc...around 3000F. Lime around half that but it does not have the mechanical properties (compression mainly), flyash is waste from the kiln some question and the heavy metals less than 1% depending on grade....It is used to bring down the OPC content since it is a pozzalan. MGO around the same temp other than light burns 800-1000F BUT produces very high mechanical and physical and chemical properties.....Not mined much in the USA mainly china. It cost more than OPC but it is coming back with Premiers efforts. If we have to ship in natural cements or other materials not at the job site we just defeated what we intended by not using OPC. MGO, lime adsorbs back the CO2 it gave off, OPC does not, like a plant that betters indoor air quality. We do the best we can to not pollute the atmosphere, and indoor air, depends on the situation and access to natural materials, politics, code restrictions, budget, etc.....

The only time a PE signature is required is for materials or methods that are not in code. Code provides inspectors data to make sure the building's are safe. Not always accurate so pad it up, the data comes from test and history and is a basic design guide even if it is not being enforced, or for people that have no experience. If you want to use a materials not code approved now you have the expense of a PE. Most cannot afford them so they follow code, hence why concrete and studs are so popular. The big impact on changing this will be code but it is filled with politics. A PE will sign off on anything that you have data for and makes the analysis or numbers work. When folks take on the PE roll that is when problems can occur. I personally would not sign off to the added dead weight on an old slab I dd not understand it's ability in this situation, drilling holes only makes it's load carrying ability worse and I'm not seeing the drainage working still unless you taper the slab to the holes. The holes would help liquid water, do little for distributed vapor pressure and condensation drying. So if I assume you have a rebar 2500 PSI mix worse case, statically I subtract a 50% due to age, 30% due to holes, 20% due to moisture traps, more if alot....now we are down to a 0-500 PSI slab...If I do a dynamic deflection check it will fail.. It won't take the pressure or flex I mentioned. Now we have what PEs refer to as a negative margin they will not for, or are allowed to.

I'm using a slab on grade and code. The extra mag strips from my walls will go on my floor. I just seen a home like this doing very well over years, looked decent. I can add solid wood planks over it or stone tile with a breathable grout since it makes an excellent sub-floor much better than plywood or OSB, hardiboard for around the same cost. The perlite core manages water/vapor and acts as a gas barrier. I have opened dialogs with my local ready mix companies...they are only interested in natural cements it I can produce more sales. I can mix my own but don't have the labor budget. Changing the way we build is not easy, not worth it for a one-off, so we do what we can.



 
Terry Ruth
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I don't recall but check ACI 318 referenced in IRC Ch 4 for slabs over existing slabs. I cannot imagine it being any less than having the existing slab lab tested for properties, and charts to follow. If there is no code path a PE is needed and they are going require the data too, a good one anyway. That will probably cost more than R&R... I'd personally do that since I don't agree with the modern day slab layers an area I don't leave to chance or compromise.
 
Jay C. White Cloud
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Hi Kris,

As you can probably tell, Terry and I are on exactly the same page, just perhaps different paragraphs...if that metaphor makes sense...

I will just hit some more points quick and leave Terry to the "meat and potatos" of this post, as it seems that this project is going down the "more main stream" path of building than natural or traditional. No worries in that, as I think sometimes folks think I am "too extreme" but I really em not, as I have to deal with (as does Terry) modern building practices all the time, and either "bridging" the two elements and/or "re-educating" general contractors, architects, etc, in what "traditional/natural" buildings can and do achieve.

>>>
I know concrete isn't the ideal material for building as natural as possible but I don't see an engineer signing off on something else.


All depends on the PE and there knowledge base. I have several (including Terry...) that more than understand timber framing, stone foundations, gravel trench/pad foundations, and the related. These systems have a history that is about 100 times longer, with more "empirical evidence" than anything we have in modern building practices.

I would also point out that we (modern humans that is) still haven't even come close to consistently and effectively employing the natural and ancient "cement" mixes of the past. These "natural cements" and geopolymer matrix have far surpassed what modern OPC can do as way of durability, strength, and much "smaller carbon foot print." So, its not concrete I despise...it is what the OPC industry has done with it to make profit over "form and function."

Drainage is definitely a concern of mine. I figured if I drilled enough holes in the existing, it would allow proper drainage. Maybe that's wishful thinking.


Drainage is everything...more important than worrying about such silliness as "frost heave." With good and properly designed drainage as part of foundation system..."frost heave" can't even take place. With just gravel and wood, there are "code approved" foundations that can be built. We (I) don't condone or use PT lumber, but by replacing this with naturally rot resistant species, there are even below grade all wood foundations that can be facilitated.

I was going to use Mag board for the walls but didn't consider it for the floor. Sounds like an option.


This is very much an option...

I would point out at this juncture, that the less material you buy...the less money you will obviously spend. I also, do understand and point out to folks that most "traditional/natural" systems can be (not always) more labor intensive, as it takes effort to process the raw materials into a viable building element.

I thought for sharing purposes, I would offer what I have before...The oldest and most enduring structures in history...still today in both practice and application...do not (nor have they ever) sat on concrete foundations. Even the ancient forms of natural concrete structures themselves do not sit on concrete ...they sit on wood or stone...for example the largest free standing and un-reinforce concrete dome (the Pantheon) sits on stone. To even take it a step further the city of Venice...which sits in water...sits on wood pilings and stone is then placed on the wood, then more stone and timber is built off of this. It has been projected that Venice would have melted into the Mediterranean centuries ago if it had been built using "modern practices."

Below are some linked sites of stiles I have worked in. All can get full PE approval if the effort is made, and none of them have any concrete used at all....

Dong Wooden Architecture

Piece sur Piece (log in log) Architecture

Just more "food for thought"...

Regards,

j
 
Kris Arbanas
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Location: PNW
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It may sound "mainstream" but I figure if I get a foundation down and my log plan set up, I can finish the rest with natural methods. I don't plan to use plastic barriers or toxic off-gassing materials in the build. I want to use mineral wool insulation, mag board walls, earthen floor etc. But I need a solid start first without a ton of labor because I am trying to start a farm at the same time.

I already have a plan so is this workable into a more traditional foundation or would I need to start over with a fresh foundation plan?

I wouldn't really know where to start with a stone foundation, that's why I was leaning towards a more modern slab. I am open to suggestions though. If I remove the existing concrete, where do I start? What is the best type of fill? I was hoping to just use low clay soil on the property. Can I follow the existing plan and just use rock/stone in place where the footings/piers are? What is the stone mixed with to hold it together? How is it compacted?

I see all of the pictures posted of these finished/old stone foundations but no breakdown of how they were created so it's hard for me to imagine. Is there any good diagrams out there of a traditional stone foundation?
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Rick English
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Would it be feasible to put a drainage ditch around the slab? That would help reduce the below grade problem.
 
Terry Ruth
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The problem is not just a below grade issue, it is also a slab above slab issue too.

Kris, are you being code or sub-division controlled? That will help determine if you have to take a mainstream path or can go unconventional. That will define your cost. You are definitely on the right track with your walls and roof, mag. mineral wool, mineral silicate paints, very nice, but if being code enforced there are some things about it you need to know to get past inspection, especially if you are being IRC and IECC (Energy Code enforced) enforced....Check with your local inspection office, developer, HOA, and make sure you understand your restrictions. Also check FEMA's 2015 flood plain map, and the site soil map to understand how well it drains, expands, shrinks, etc...Slab on grades are new and broken in today's traditional sense, there are some things you need to know to get them right as far as sub-slabs, drainage, and existing concrete is not good. I'll send you to George Swanson his advice is not free. I'm using a zero entry slab since I am being controlled and George, a Chemist, and Biologist, are reviewing my plans.

If you are not controlled I recommend you listen Jay the master. I do not know as much as him about history and need to reread his raised earth foundation again.

http://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm
 
Terry Ruth
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Lazlo, hit me later where I think you are going with that question. We want the wetted or surface area to be able to drain/desorp by gravity capillary action down to clean rock or recycled glass. We cannot control this natural action or surface tension to boundary layers/drain tiles practically, like flowing liquid water. The other action is capillary suction from the ground/expansive soils/gases up due to humidity/pressure gradients. This one causes high humid indoor air, radon, emittance of the slab, wall and rot especially in basements surround by four buried walls.

Mainstream answer is plastic sheet where dew or cold condensation collects, foam insulation to attempt to move the dew temp to it, along with the fungi foods, rips, tears, structural issues, etc. Having a slab below a slab in affect compounds this issue. A mainstream site would probably advice putting plastic/foam over the existing slab and pouring over it. There are better materials and methods to manage this.
 
Kris Arbanas
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Location: PNW
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Terry Ruth wrote: Kris, are you being code or sub-division controlled?


Well it depends. Have I got a building permit etc yet, no. Am I rural, hidden and could I just start building whatever I want, yes. The main issue with avoiding code or inspections would be what if I get caught somehow. How is my place sold in the future without any record of house being built there. I couldn't advertise the property with a legal home when selling. I do plan on staying for life though, so the idea has crossed my mind several times. I also don't have the confidence with my limited foundation knowledge to just "wing it".
 
Jay C. White Cloud
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Hi Chris,

I feel for your struggle with all this...but it doesn't really work the way I believe many thinks it does...

It is really difficult sometimes for those here that fall into "professional builder" category and those that fall on the spectrum between:

Completely niavie DIYer with big dreams and a very strong "I think" belief in what they can be achieved.

to...

Someone that just knows enough to worry about what they are trying to do...

I know some that have "taken the risk" of building outside of "the authorities." I don't know a single one that is ever really at peace or doesn't eventually loose out. My advice has always been:

Learn to "work the system."

or...

Find where the system doesn't exist (or isn't strong.)

I see other challenges and many "I don't knows" about you project that go well beyond what to do with the slab...

Where are the logs coming from? Who is going to lay them out and joint them? Do they actually have the skills, or is it just another "kit company?" What is the soil type? Does Kris have a tractor or other heavy equipment to make building this "time plausible" to the description of the project parameters? Is this current slab even capable of taking the massive point load weight of a log wall system and its interior timber framing without buckling or failing?

Some of these may have no bearing at all on the project and just be my own worries and "unknown's," while other may even be more dire that I think they are already. It is really difficult sometimes to start giving "good advice' when we focus too quickly on such a narrow view of a project. Just some things, besides the slab and permitting that has crossed my mind.

Regards,

j

 
Terry Ruth
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It doesn't work that way. A requirement to get a building permit can mean ALOT of things. Call your city or county inspection office and ask what code is being enforced for single family residences, IRC 2006, 2009, 2012, 2015? Also, if they have excluded any Chapters or re-written them, or created their own building standards. For all you know they could care less what you build, they just want to know about it and get there little permit fees. Also ask if an Energy code IECC) is being enforced..

https://law.resource.org/pub/us/code/safety.html

That will tell you what is being enforced at your state level that can differ per county, city, town. You may only have zoning codes.

If you are planning on loan talk all this over with the bank they will have inspections, appraisals. That is why I say building natural can come with a steep price in training and proving your build, unless you are way out in rural and paying cash, then noone gives a hoot!

Let us know so we can advise better.
 
Kris Arbanas
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Jay C. White Cloud wrote:

Where are the logs coming from? Who is going to lay them out and joint them? Do they actually have the skills, or is it just another "kit company?" What is the soil type? Does Kris have a tractor or other heavy equipment to make building this "time plausible" to the description of the project parameters? Is this current slab even capable of taking the massive point load weight of a log wall system and its interior timber framing without buckling or failing?



The douglas fir logs are harvested locally here on Vancouver Island. I am not using a kit company. They have been crafting log homes since 1975 and everything is done by hand. They will do lock up which includes foundation but that would just be a battle for how I want it finished so that is why I only want the log work done by them. They come to my property and set it up and fit it properly. I do have a concern of leaving the log set-up over our wet winter if I don't have time to get a roof on in time. Ideally, I would like to do a lot of the work with with family and use douglas fir from my land for roofing and interior but it comes down to how much time I have before winter. I may be pushing it for time but next year it will be all farm so I want to get something started this year.

I know there is clay soil on some spots on my land but I will ensure that the fill I use is from more sandy spots. I do have a small 36HP tractor that has been a workhorse since I took over the property. I wouldn't have gotten anywhere so far without it lol. I was going to rely on the engineer to ensure the point loads are carried sufficiently and maybe add additional reinforcement since you mention that OPC has poor strength in comparison to stone. Can the strength be improved significantly with a combo of stone and cement for the piers?
 
Kris Arbanas
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Terry Ruth wrote:It doesn't work that way. A requirement to get a building permit can mean ALOT of things. Call your city or county inspection office and ask what code is being enforced for single family residences, IRC 2006, 2009, 2012, 2015? Also, if they have excluded any Chapters or re-written them, or created their own building standards. For all you know they could care less what you build, they just want to know about it and get there little permit fees. Also ask if an Energy code IECC) is being enforced..

https://law.resource.org/pub/us/code/safety.html

That will tell you what is being enforced at your state level that can differ per county, city, town. You may only have zoning codes.

If you are planning on loan talk all this over with the bank they will have inspections, appraisals. That is why I say building natural can come with a steep price in training and proving your build, unless you are way out in rural and paying cash, then noone gives a hoot!

Let us know so we can advise better.


I will have to look for Canadian versions of the resources you posted Terry.

My plan is to go in debt free so hoping to avoid the bank altogether
 
Jay C. White Cloud
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They have been crafting log homes since 1975 and everything is done by hand.


This sounds like "scribe fit log work" and you do have some very fine companies out there. What will be the method of "chinking" and "daubing" between the logs...modern or traditional? What size log are being employed for exterior walls? 250 mm or 300 mm?

I do have a small 36HP tractor that has been a workhorse since I took over the property.


Excellent, they really are a time saver when under the gun to beat weather.

I wouldn't have gotten anywhere so far without it lol. I was going to rely on the engineer to ensure the point loads are carried sufficiently and maybe add additional reinforcement since you mention that OPC has poor strength in comparison to stone. Can the strength be improved significantly with a combo of stone and cement for the piers?


If you have a PE that knows traditional building, that's great, if they don't, often they can add more challenges than help, as they over compensate for not understanding how systems work...so...won't take the risk and revert to "modern methods" they know and understand.

When I am forced to use OPC because of exactly what some PE do (like I just referenced) I only use high strength fiber reinforced, and will not allow rebar or any metal inside the concrete. This will only corrode and spalled the concrete in a few decades. This is one of the major contributors to why the concrete and steel infrastructure of North America is falling apart..."oxidation expansion" (aka rust jacking.)

At this juncture, I am only "following along" and offering no feedback unless asked specifically about something. For a project like yours...I would use zero concrete and the slab would just be considered a "soft limestone" rock to be either "resurfaced in areas, broken up and repurposed for "walling and terracing" and/or covered up with a raised earth foundation system of podii or dais style foundation depending on the soil types, angle of repose, and drainage characteristics for the site.

 
Kris Arbanas
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The logs avg between 11-12" so closer to 300mm. They don't actually use any "chinking" but notch a groove on underside of log that creates a weathertight seal and only add a little insulation.

That's interesting about the rebar/metal. My plan calls for reinforcement on all of the piers so I'm sure they would want a ton of rebar in them. What kind of fiber do you use in your mixes? If the problem with concrete is that it constantly holds water, wouldn't the fiber decompose? Does small stone added to concrete add any additional strength?

I like the idea of a podii style foundation but I am concerned with there not being any undisturbed soil underneath since I need to either bring fill in or move it in from the surrounding land to fill the existing hole. Do you think there would be an issue if the soil/fill type is right and I properly compact?
 
Jay C. White Cloud
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The logs avg between 11-12" so closer to 300mm. They don't actually use any "chinking" but notch a groove on underside of log that creates a weathertight seal and only add a little insulation.


That is an excellent size...

The insulation, in this application, is considered the "chinking and the daubing" both. I hope it is a "mineral wool" and not a fiber glass or foam?

That's interesting about the rebar/metal. My plan calls for reinforcement on all of the piers so I'm sure they would want a ton of rebar in them. What kind of fiber do you use in your mixes? If the problem with concrete is that it constantly holds water, wouldn't the fiber decompose? Does small stone added to concrete add any additional strength?


Stone does not add strength per se, and the fiber is a synthetic either of glass, carbon, or nylon. Fiber re-enforced OPC has become more and more common in many areas. As you know, I dislike OPC materials a great deal, but if forced by circumstance to use them, fiber reinforce is the type I prefer.

I like the idea of a podii style foundation but I am concerned with there not being any undisturbed soil underneath since I need to either bring fill in or move it in from the surrounding land to fill the existing hole. Do you think there would be an issue if the soil/fill type is right and I properly compact?


To actually build or form a functional podii system foundation one must start with bare mineral soil and build up from that with stone, clay soils and lime. There are many different methods and systems all similar in style to each other for this. It would be hard to say in you application what (if any) would work, and I don't think it probably is applicable with the slab already there. The more I read through this post, the more I lean towards a "do over," as that slab now is for a different building and different loads. I also am rather obsessive about getting buildings off the ground by at least 500 mm or more, as is found in most vernacular systems.

Regards,

j
 
Terry Ruth
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We been adding glass and carbon fibers to phenol resigns/catalysts for decades. Better than resign alone by far, but not as strong as continuous fibers like bassault, if the budget can afford it....glass is weaker than carbon, e-glass is stronger than s. We use e-glass often, carbon much more often. I'd like to see some chemical test of fibers corrosion embedded in wet concrete over time including helix I did not find on thier site. Just like rock is an aggregate that needs a binder to give it more strength so does chopped fiber. Just like rebar the fiber needs to take out the tensile and bending loads when the slab goes into deflection, at the upper surface of the slab, that is it's main roll. Rock aggregate does little for shear/tensile (hence rebar) in this design, does more for compression that is low is what I think Jay was eluding to. HELIX carbon fibers are shaped like a drills pull or tensile resistance, so it works to take out tensile forces in torque, much better, and grabs on to the binder better, just like sharp rock can it's binder. Look into HELIX let me know what your slab cost now. Others fibers the manufactures will recommend use for shrinkage only, not continuous loads or fatigue. Since they put the rebar at the neutral axis it in theory sees no bending or compression when the slab deflects. Walking loads on a slab are not high, 500 lpf, it is deflection and flex that cracks slabs. Foam or weak shear soils are not good. We get soil test the PE needs. If a continuous mesh/rebar, two layers, where closer to the lower and upper surfaces it do better than rebar at the neutral axis alone. A good PE would spec continuous connected fibers or metal at the slab or wall bending joints in seismic zones greater than C, wind 90 mph. In tornado and hurricane alleys that s/d 200-500 mph winds which puts the stick lumber industry out of business but saves lives.

btw "POINT LOADS" are just that, act on a point like a rock hitting a windshield. Column or post or beam loads react over a larger areas (4x4, 6x6, etc) in compression and is just one static check or area of concern.

If the density gets too high from fibers or rock the concrete will not drain well and will thermally bridge easier, also the deflection or flex modulus property will get too low and will crack in deflection/bending. Designing a mix should be left to professionals. Ultimately, if you deviate from code a PE (structures engineer) needs to sign. The problem with "PE"s is most are schooled and trained as structures engineers, not biologist, physicist, or chemist. We took 2-3 levels physics-chem enough to get familiar with it in college but the licensed PE test is a structures test totally different mainly statics and dynamics. An Architect is trained to know when to call a buiding physicist, chemist, but some don't know that much. I think there are some exceptions to the rules but, this is big issue at the home design level, people not having the skills to design. That causes more issues in slabs and structures than anything. I agree with Jay putting a big plate (slab) over earth or soil makes no sense, nor all we do to make it work along with all the grey areas. Need to understand wind and seismic or resulting dynamic bending loads, moments of inertia, just to get started!

500 mm(1.6 feet) off the ground won't work for my old folk zero entry design, nor get past ADA baby boomers are requiring. The more I think about zero entry the more I like, why create a trip hazard for even infants in strollers if we can avoid, or carrying groceries, furniture, etc....same in wet shower areas. ...grade slopes, large overhangs and gutters can get it done. MGO slab properties would get the same strength as opc/lime with fas less tensile reinforcement if any at half the thickness nor have all the moisture or thermal issues @ less than half the manufacturing temp and carbon footprint.
 
Kris Arbanas
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The insulation, in this application, is considered the "chinking and the daubing" both. I hope it is a "mineral wool" and not a fiber glass or foam?


Good point. I will ensure they use mineral wool if possible because I assume they wouldn't.

Stone does not add strength per se, and the fiber is a synthetic either of glass, carbon, or nylon. Fiber re-enforced OPC has become more and more common in many areas. As you know, I dislike OPC materials a great deal, but if forced by circumstance to use them, fiber reinforce is the type I prefer.


Are these usually added at the site or in your experience will concrete companies add them before leaving the yard?

To actually build or form a functional podii system foundation one must start with bare mineral soil and build up from that with stone, clay soils and lime.


Interesting. I would have assumed that clay would have to be kept to a minimum for proper drainage. I guess some is needed to bind the other constituents together?

I don't think it probably is applicable with the slab already there. The more I read through this post, the more I lean towards a "do over," as that slab now is for a different building and different loads.


I am convinced after reading yours and Terry's suggestions that removing the existing concrete would be a good place to start.


Terry, from what I can see on the Helix Fiber website this is a steel product with zinc coating. Will this not eventually suffer the same fate as rebar/mesh in the longterm? Or maybe I'm looking up the wrong product because you mention it is a carbon product.
 
Jay C. White Cloud
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Hi Kris,

Insulation between logs:

Glad to read that this project will use mineral wool between the logs...at minimum application. This could also be called "gasketing" or "caulking" (in the historical since.) If you care for a more traditional method and material "oakum" is what was often (is often) employed in such applications, which is treated with "flax oil paste." It is probably a tad more labor intensive, but I believe give a much better "seal" to scribe fit logs and can be used alone or in concert with mineral wool as well.

Concrete:

General "Concrete Companies" are getting better, and probably moving faster than the OPC manufacture themselves for trying to lower their carbon footprint and offer better means, methods and materials. They will add fiber for you if requested and the better companies have a full range of types from long strand spectra/kevlar, to carbon fiber to just plain old "20mm glass strand" many even have PE on staff or as consultants to give "targeted specs" to the load demand of the footer, pads, posts, slabs and/or stem walls. As stated before, some even offer "limecretes" and "geopolymer" mixes now.

Yes, there is concern with many of us and some evidence over time that the "Helix Fiber" could suffer oxidation and "rust jacking." In an application such as yours, if within the "drip line" and out of heavy moisture exposure, this..."may not"...be such an issue. I personally avoid the addition of any mental reinforcement to OPC if it can be avoided, and still meet load parameters.

Clay and the Podii system:

In forming traditional "podii" (aka dias) and other "raised earth foundations" the clay is restricted to zones underneath the "umbrella" or protected zone of the roof's often extended "drip line." Here there is little issue with it interfering with drainage, as it is sitting on or is part of a stone and gravel pad, and drain channels that extend and grade away for the structure. Some of these in more elaborate designs will all run to a pool and these are how many of the Imperial and Japanese water gardens are fed.

Architecture Off Grade:

Terry Ruth wrote:500 mm(1.6 feet) off the ground won't work for my old folk zero entry design, nor get past ADA baby boomers are requiring. The more I think about zero entry the more I like, why create a trip hazard for even infants in strollers if we can avoid, or carrying groceries, furniture, etc....same in wet shower areas. ...grade slopes, large overhangs and gutters can get it done.


Perhaps we do differ here on this point Terry...just a bit...

All the longest enduring architecture comparatively is at minimum 500 mm off grade, relative to many "modern concept" structure today that are at or below grade and suffer the ill effects from it. Even in "historic examples" still surviving, any that are closer than 200 mm from grade reflect considerable degradation from this close proximity. In the "elder house architecture" arena, I have help edit a few books for publishers and it is a mis perception that these "need to be" or "should be" at grade (aka "zero entry.) Many actually are multi story communal living center type architecture, while others are a form of "cohousing" cottages that still follow a vernacular them in design, with raised foundations and wrap around porches that lend themselves actually very well to "wheel mobility devices" and other walking aids. All of which meet or exceed ADA standards. I should also share that I have sat on ADA boards for not only architecture, but Challenge Courses and Gymnasiums. Being "close to the ground" has nothing to do with these standards at all.

I place "zero entry architecture concepts" in the same category as "zero roof overhangs" which both these have become common practice in contemporary buildings all over the nation, and both are already suffering the ill effects from that move away from vernacular systems of "being above grade" and having "extended eaves and overhangs." These modern concept "zero entry" structures all suffer from various degrees of ill repare from this low to zero grade design in every example I have inspected or seen. They all suffer from, at minimum, "splash up" degradation to other "water infiltration" issues at both the eave and the foundation grade line. I would suggest being even several feet above grade, if the landscaping and other design elements are properly effectuated, have little affect to even "wheel bound" and "limited ambulatory occupants" (from neonatal condition to geriatric infirmity) and should never be a safety hazard of any form in architecture of good design and building practice.

Asian homes (many if not most sit on posts and/or a dias foundation) have been some of the most "copied" in design history format form "Green and Green Brothers" during the "Craftsman Movement" to the more "Parier Styles" of F. L. Wright. These homes almost always (when designed well) sit above grade some distance, and/or the landscaping is terraced accordingly to achieve the same architectural affect.



 
Terry Ruth
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Gents, I accept the challenge to be the first ever in the world to effectively design and build a zero-entry slab-on-grade home. Who knows maybe when I reinvent the wheel re-write history, they will create a "builders hall of fame" just for me Then I retire early. Just kidding! They been here in the high dry deserts for centuries no issues. It rarely rains and if it does it is so hot all year it evaporates fast. The word 'moisture' they only wish for. There are no gutters/overhangs on most homes either. I believe it is impossible to give advice that applies in general to all climate zones, all building designs. There are too many factors. Having lived in many US climate zones I have seen drastic differences. Kris, I believe you are in a Marine, been there too Seattle....there those people are the opposite, it never seems to stop raining and they get thrilled when the sun comes out.

Must have been basalt fiber-swirls I was thinking of. I agree with Jay other than stainless that is expensive, metal in general is just asking for trouble, especially in Marine or salts, the corrosion protection eventually wears off. I'm reading some basalt (BFRP) and other composite reports and code paths, along with Premiers MGO cement admix which drastically changes concrete properties. The basalt rock would improve the way we make concrete. I'll go into this and how my wall design only gets better when it sees moisture, water here soon: http://www.permies.com/t/48019/natural-building/Indoor-Air-Quality-Healthy-Building

Here is what I was talking about and what happens when slabs get to thick or cant flex below. The ductility or flexible modulus goes down too far it can not bounce like a trampoline from low strength or high expansion soils, live or dead loads, etc. The plasticity and how far it can stretch before rupture/crack in tension has to do with stress/strain or Modulus of Elasticity (MOA). Non-corrosive Basalt rock has high FM, MOA, and around twice the tensile of steel, much higher than any chopped fibers in the mix. . It is mechanical the physical properties we shop for, but have to understand the test to get them since they can be misleading. What is important is how cements bind to rebars or fibers over time and I still have yet to determine. Non-corrosive materials do no good if they do not resist bending, have low flex-ductility, tensile, MOA. A lot to it. Cost and lead time can have large impacts on what materials will work in a locality too.

My ready mix company's do not have any of this available due to low demand and high cost, and I have around 5 big ones. I'll have to pay more as you will more than likely will too, or mix on site.

https://en.wikipedia.org/wiki/Flexural_strength



 
Jay C. White Cloud
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Hey Terry,

I am sure you will pull of a version of it my friend...no doubt. I also bet you a cup of coffee, when it's all said and done...it will be a "net zero entry" like so many in Japan that rely on the landscaping and architectural design to achieve it and not actually so many that do fail because they are nothing more than a thin slab at or below grade.

They been here in the high dry deserts for centuries no issues. It rarely rains and if it does it is so hot all year it evaporates fast. The word 'moisture' they only wish for.


I can see and understand that completely in such an arid area. Where my Brother In Law lives in Arizona this is a common practice. In these regions, "net zero" is part of the vernacular with...some...systems. Yet even with Hopi, Deni, and Pueblo many sit on a landscape that itself is raised to facilitate drainage away from the architecture. Then I can see, understand and support a "zero entry design."

I am glad you brought up..."gutters"...!!! One of the sillies and overdone modern architecture features there are. I see them everywhere now days...and guess what...they almost always don't work, are out of context of the vernacular forms, and only rot the side of a house out. Traditionally they are only at ingress/egress points and are very well maintained with good separation away from the side of a structure. Water, in my view, needs to come off a roof as far from the house and foundation as possible...hit the ground...and go into it as fast as possible. If it is going to be recovered for use, it needs to be done below grade and not dampen the soils around the house at all. Cisterns are great...but must be well designed and understood to function well and endure the centuries they "should" last.

You also have brought up another point Terry that so many novice, and even "expert??" designers try doing...generic, and broad spectrum design! Regions and biomes have developed functional styles...when we try building a house right at grade (or below) and it is a damp area or flood plane...well...not a good idea. Just like now is happening all over Louisiane with "zero entry and zero roof overhang." It hasn't even been ten years and many of these home are in such a horrid state that many are already badly damaged from this trend brought there after the major hurricanes of the past decade.

Basalt fiber-swirls have great promise and application...I have had it in a few slabs. I think this "new" old technology could vastly improve our road beds, bridges and should actually replace rebar along with carbon fiber, and some of the other long chain synthetic fibers. Combine this with the geopolymers and we actually start seeing "concretes" that have low carbon foot prints, and last the millenia that its Roman counterpart have. BFRP is another of those positive steps forward...

Regards,

j
 
Kris Arbanas
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Any experience or thoughts on this product? http://www.fibermesh.com/product/microsynthetic.html

It is what my local mix company uses.
 
Jay C. White Cloud
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Hi Kris,

That is one of the micro fiber (they do make larger stands too) for inhibiting (actually stops any at all from what I can tell) cracks. I have seen it on a few jobs and for OPC work, I like it and think it or a form of it is a "must have," for any "good" concrete work.

Regards,

j
 
Terry Ruth
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My best advise in this situation is hire a good LICENSED or at least 4 year DEGREED Engineer w/least ten years applicable experience and proven monitored designs IN YOUR CLIMATE ZONE. Jay is correct the three dimensional fibers do alot to resist loading I will cover in the thread I linked to. It's not simple, however, hence why the ICC letter points to ACI 318. They list no mechanical properties/physical test data that is where the average person trying to design a slab will get lost and make costly mistakes. Major lack of 30 year life cycle testing, more less 500 year. I'll take a close look at this material, and the other major fibers and specs I have been manufacturing and designed to for decades that are proven, monitored, for 20-30+ years..... Ironically, we were just told yesterday on a major world class program I am on there is a shortage of carbon, prices will skyrocket once again and it is the king! I imagine we are big part of that shortage in the USA. I'll also address international code that does not allow slabs at or below grade, the slope, load, requirements that are clear as day in the IRC/IBC.

I also do not suggest a person uses MGO board or Basalt rebar w/o having such an Engineer hired! ...and a reliable China or Russia supply chain.
 
Terry Ruth
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FYI, IRC 2012. Take particular note of R401.2 "requirements" for loads. Soil testing (under 1500 PSF), wall/roof to ground loads based on dynamic wind/seismic conditions. FRPs (fibers) driven by ACI 4401R-06/07/08. Lots of math (or professional code/test interpretations) a person (homeowner, builder) does not understand do not try it and guess or take opinions!
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Terry Ruth
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BTW Kris the same ACi international spec/code applies to CAN IF you're AHJ accepts it is another story, but needs to be understood in any case. If not the need to hire a PE/Physicist/biologist and he'/she will need the same data or should to sign off on your drawing(s), if a person is wanting to take on the Architect design role. in that case, I'd suggest BOTH or all professionals be involved. R&D budget to get it right just went through the roof is my guess but do crunch the numbers and see for yourself. Change comes with a price tag! Definitely not as cheap as some on the internet make it appear.
 
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