Foundations: capilarity, frost heave, pest damage

Hi folks.

First of all, i need some venting and also advice.
I am doing this for some months now without a very clear ending in sight.

Second, this thread is related to the "Raised earth foundations" thread on this same forum (sort of "what one stumbles upon when trying to apply what he learned" continuation).

There, the crux of the matter is:
- soils containing clay are sensitive to water; variations in water quantity lead to swelling / shrinkage which will destroy any foundation if it's severe enough;
- soils containing water are subject to frost heaving in climates cold enough (but only to a certain depth called frost line);

The solution, as portrayed there, is to replace the soil (basically the clay) with free draining medium, basically several lifts of compacted rubble.
One simple example of such a foundation is the gravel trench.
No clay - no swelling.
No water - no frost heaving.

After reading said thread and doing some (a lot) of research, i said to myself:
"Hey, this looks pretty nifty, i can do this easily"
Silly me ...

Later edit:
Since i was asked to explain some abbreviations, here they are:
PE = professional engineer (with a license)
OPC = Ordinary Portland Concrete
RC = Reinforced Concrete (with steel rebar)
Pad Foundations - foundations consisting of solid blocks (usually OPC or RC) going down to or below the frost line, connected above or below ground by foundation beams (usually RC).
Above these pads sit posts carrying the structural load.
Here's an example:


Of course, we live in the "civilized" world and most places such a foundation is outright laughed about if not burned on a stake for witchcraft.

I am in such a situation and have the great "pleasure" to discuss it (on my time and spending) with one of the greatest PE's around.
Now, please bear in mind, he knows several old buildings / techniques, but he's still very much in the OPC camp.
And the world we live in has so much OPC that the only fix is more OPC (more on this later).

So, i asked for a foundation on a strawbale house, single floor, wood post and beam, superduper light, strip foundation as that's something very agreable to them (PE's).
Yeah, also using rubble trench below grade and stone stemwall above, simple enough i guess.
WRONG !!!

Ok, then, what about PAD foundations ?
The Japanese do it with high levels of success, mind you.

Ok, he said, but only in highly RC, otherwise no chance of ever seeing a permit.
Got it, since concrete is what it's all about, i'll bite, at least it's just a small amount.
Yes he sad, but he recommends something different, something better.

Now, i'm curious.
So what he recommends ?

The same trench but filled in OPC instead of rubble.

And the stem wall  
Same width of the trench and filled with OPC and the top with RC.


Wonderful, i said.
So, that's why it's better, since it's MORE (concrete).

But i really want the pad foundation.
He bulges, and here we get to the crux of the matter (and the meat of the title).
You WILL have issues he said:

Him: As the RC beams tying the RC pads sit above the ground, you will have pests (rodents) getting in by going beneath them;
Me: I'll fill up the space;
Him: If you do that, since your structure is light, frost heave will lift it and break it;
Me: So what's the solution (i think i know where he's going) ?
Him: The beams must span below ground so rodents don't enter and must be low enough so frost heave does not affect them, best to the frost line;
Me: But this will effectively make it a strip foundation, with all the concrete i don't want;
Him: Yeah;
Me: Screw it, i have better ideas. Let's replace that below grade space with rubble, crushed stone, etc.
No water, no heaving. No clay, no swelling;
Him: Ok, but rodents can enter and water also;
And water will stay there with no place to go and when winter comes, it will freeze and heave;
Me:   No way, the soil at the bottom will suck it up. Look at the soil sample (i did the best i could buy).
31% clay, 62% dust, 7% sand.
45% porosity and 19% natural humidity.
It WILL suck it without major issues, unless it's THE FLOOD again, in which case there'll be bigger issues.
AND, i'll also do a sloped away area, just to the outside of the foundation, so water can drain away;

In the image below, only the RC beam is shown, without the below grade pads.


Him: Ok, but water won't go where you want to, but where water wants to.
Better put a concrete pavement around the foundation so water won't get there;
Me: Right, and those things work.
I've seen a lot of buildings built like this, lots of concrete, concrete pavements alround, yet still very damp, plaster / paint coming off the walls.
It does not work;
Him: But we have places with gravel around and they are damp and moldy.
So we poured concrete pavements and problem is gone;
Me: Because they were done wrong, and also because they were HUGE stinking piles of Friggin CONCRETE;
Him: Yea, concrete is like a sponge, that's why you need a damp proof layer, a plastic sheet;
Me: THAT'S WHAT THE GRAVEL IS FOR          !!!
Plastic won't fix it.
Water can get in, you just have to make sure IT CAN GET OUT / AWAY !!!
Him: But water does not get "out or away", it just stays there and causes issues like frost heaving, etc;
Me:          
Him: OK, we can do a pad foundation like you want but it's your problem if youhave pest / moisture issues.

So, long story short, continuing the "raised earth foundations", for what looks like an inevitable RC pad foundation:
1. What about them pests (rodents) ?
2. what about the water infiltrating ?
3. what about that frost heaving ?

PS
Sorry for the long narrative, i could not express myself otherwise.

It sounds like you are doing what I did once for a woodworking shop (now converted into a lambing barn), but honestly I do not know. Now, not to be snarky with you, but I must also admit I have no clue what half your abbreviations are for, and I suspect many others on here do not as well. You might get a few more helpful replies if you edited your post to explain some of the abbreviations.

OPC = ordinary portland cement.
RC = reinforced concrete.
PE = professional engineer (with a license).
Pads in this case probably refer to what are also known as spread footings, which can take a point or line load and spread it over a wider area so it will not sink into the earth over time.

31% clay actually sounds like a rather high percentage, and I might be concerned about its drainage and frost heaving properties. But as long as it is dug out to below frost line and replaced with rubble draining to daylight, there is no reason to worry about that. You should determine if the soil is expansive (swells and shrinks depending on water content), as that can destroy pretty much any foundation. A professional can tell you how much is okay.

Sorry for the abbreviations, i added some explanations including what pad foundations are.

In my neck of the woods (and in the countries around), hollow brick encased in reinforced concrete (posts and beams) is the norm.
That usually requires continuous foundations down to at least the frost line made of concrete or reinforced concrete.
This is done because the usual homes are heavy, usually having 2 levels with concrete slabs.

But for a light, single floor wooden structure with strawbale infill, this is insane.
Since the building load is low, a grade level beam is employed above grade, usually in reinforced concrete.
This beam is basically a stem wall.
This is supported below by pads (60-80cm / 2-3 ft square footprint) that extend below grade to at least frost line.
These are done in plain or reinforced concrete.
A reinforced concrete post sits on top of them and supports the stem wall.
Sometimes, to save labor costs for the forms (but increase concrete usage), these posts are left out and the pads extend to grade level supporting the stem wall directly.
The pads are placed directly under posts, at corners and intersections.
This saves a lot of material cost (mainly in concrete).
It also has the advantage of less direct soil contact since concrete is a moisture sponge.


Regarding soil properties, 31% clay does seem to be a lot.
However, soil porosity is 45% so water infiltration and clay expansion has enough space to take place.
Besides, the humidity at the pad level will be pretty constant year round.
It's the surface humidity that's gonna fluctuate, the most critical part being beneath and around the ground beam / stem wall.

Frost heaving makes the soil expand by 10%.
If the soil is replaced by rubble, there's no water to freeze.
Even if i don't replace all soil down to frost line, the remaining part will heave less.
And the rubble can take some of that heaving pressure since it can move a little.

I am looking right now at a built house plan that uses the same foundation type.
It has floor + first level, and stem wall is 1m above grade and 15cm below, sitting directly on the pads (blocks).
My plan is for 0.5m above grade stem wall.
I can see this structure is about twice the weight as my house and the stem wall goes 15 cm below grade directly over soil.
There's no frost heave under the pads but there is under the ground beams.
It is said that weight alone can counteract frost heaving pressure from below.

It also has a concrete slab over the stem wall with plastic membrane underneath, which is said to help with moisture coming up from the soil below and keep rodents out.
I don't want a frigging concrete slab in my place, but i will use a layer of gravel 20-30 thick for capillary break.

Hi folks.

I have some images of the "thing" and what i think would work.

And the gravel trench 1.5m away from the stem wall, dug down to the frost line.
This should be around the whole foundation, i put it on one side just for illustration.

Topsoil will be removed on the entire surface of the house + 1.5m around it at a depth of about 20cm.
Starting at the inside of the stemwall, soil will be removed so there's a slope to the gravel trench.
1.8m horizontal @ 0.7m vertical yields a 0.4/1 slope or 40%, enough to make any water go quickly to the trench.
This trench can also slightly slope to a corner at a deeper hole in the ground.

This would make sure no rain water can get in the gravel bed below the house.
Water table is at 3.9m below so not much to worry.

Also, i plan on using some pavement / sidewalk around the foundation which will make 90% of the water go to the trench and not elsewhere.
I would prefer stone slabs but availability and costs may show other solutions.
Concrete or plastic sheet, as recommended, will not be welcomed.

Now, all this gravel will make drainage excellent and break capillarity completely.
One other thing will remain : pest access.

I know rodents like to dig thru some pretty hard things, i imagine a gravel bed won't stop them if they really want to get inside.
I've tried with great deal of success broken glass embedded in soft mortar and i think mixing some in the critical parts of the gravel will work.

I have not heard locally anybody complaining about insects (ants) getting in from beneath but that may happen.
For this i have no idea what to do.

Thank you for the clarification on the abbreviations, and sorry I was not so intelligent to know what they were. I am not an engineer or architect as you can tell; just a dumb sheep farmer.

But I do like the plan. I have always loved the concept of grade beams, and am quite sure they will work well, especially where I live on a 6% grade on top of a hill. I am even at the height of land of two water sheds, the water here has two places to go...North or South but it is not staying so finding daylight at the end of my trenches would be easy. My plan for a garage was to dig the trenches below frost level, fill in with rock, then pour a grade beam over that. Then I would build my garage above. For what would be my "concrete slab" I would first put down 2 inch Styrofoam for a capillary break and insulation, pex pipe, a layer of sand for heat distribution, then crushed rock over that. This would allow me to work on my bulldozers and other equipment under cover, on top of radiant heat, and without damage from the tracks on top of a concrete floor.

Here your plan though is overkill, we would just set the grade beam on the fill, but we have gravelly loam here so it is far different then what you are dealing with. And it is refreshing to hear someone wanting to stay away from concrete realizing it is a sponge and not "waterproof".

As for rodent control, one trick we use here, and I am not sure how you could incorporate it into your design because I am not sure your embedded glass would work well, is when putting small buildings or camps on piers, to put a big flat rock on top of the pier, but under the sill. In this way the rodents (mice and rats) fall off when they go to climb upside down on the cantilevered big flat rock. I hope you can picture it. It would not be hard to do with precast sections, or just buy big flat rocks. Anyway just an idea.

As for ants, I think I would just put down diatomaceous earth during construction and then reapply as needed.

You did not mention snakes, and in Maine we do not have big or even poisonous ones (the only state in the USA that doesn't), but I have ducks and they love ticks and go after snakes and frogs with a vengeance. Not sure how they would do on big snakes, but here ducks keep my yard snake free.

Hey Travis, don't sweat.
I am an engineer but on a completely different field (electrical-electronic).

What i think of may be overkill but:
- the area is a former swamp drained some 2-300 years ago so there's some water below (not on my plot but other places water is just a foot below grade)
- the building codes are idiotic (almost nothing but pure concrete - they are working on forbidding stone)
- no one steps one inch outside the codes in the big cities
- my plot of land is 500m away from the big city ....
- concrete is a be all fix all ... unfortunately ...
- i (practically a nobody) am banging heads with one of the greatest building minds in the county (as per my dialogue in the first post) and we're both hard headed.

I could of course do it my way, would turn out much better from all points of view, but no permit ...
And i'm already tired of the ridiculousness of the whole reality thing ...

Oh, i just finished rechecking what kind of concrete and cement is less susceptible to water infiltration ...
Hint : it's the kind that's not available
And what type is available ?
The one with 100% portland cement, the most spongy one ... bleah ...
Well, at least they say it's the least susceptible to "cold" whatever that may be ...

Regarding rodents, i know that solution, it's good for suspended, on piers, above ground structures.
What i'm describing is on top of grade structure (the least bad the codes present - sadly on it's way to elimination).
The broken glass is there for one reason only (and it works, i've tried it): if rodents dig thru, they get they're nice little noses / lips cut by the glass.
They get to live and tell the others : ON"T GO THERE AS IT'S NASTY.
Killing a rat will take out one from the list but if he has a terrible experience and gets to live and tell the others ... well, rats are not stupid, they will listen.
This is also verified knowledge.

Now, back to banging heads ...

Interesting, PE's tend to be so rigid in their thinking because of the way they are taught.
If you listen to a PE long enough, you will wonder how the heck any of the 400+ year old buildings in Europe are still standing, since none of them have foundations that would meet PE approval.
In the original 13 colonies in the USA, there are fine houses built on stacked stone (mortar less) foundations, and they are still standing, no heaving, no water infiltration or any other disasters have happened to them.

The real trick to a good foundation is to have it wide enough at the bottom so that all born weight is spread over a wide area and that it extend at least a foot below the deepest frost line for the area.
the wide foot will support more weight with out settling (physics rules). Even "modern" foundations that are poured concrete need a packed gravel base layer so water will drain away.
I worked on a house in up state New York back in 1967 that had a dry stacked stone foundation, it had been built in 1736 and was still in good condition. The basement had a dirt floor and I never saw that dirt floor wet, even during major rain events or after them.
At that time I was working with a PE and he could not fathom why that floor remained dry. It stayed dry because they had installed a gravel trench all around the base of the foundation back when it was constructed that was 2 feet wide and at least a foot deep.
The rock walls of the foundation were 2 feet inside to outside and two layers that were laid in a locking manner, same as they used to build solid brick walls. The house had 6 inch by 10 inch base beams that laid on top of the foundation walls, 2 feet above grade.
The house was a Timber Frame and all the wood beams were jointed very tightly.

I think that if you pay attention to what makes a good foundation, below the frost line and with proper attention to drainage, any such foundation will work very well.

Redhawk

Bryan, my dear friend, you spoke to my heart.
What you said is what i already spoke to the PE.
I even made a small, 16page, dissertation on what i want, how i want, and for how long people have done it like that with tremendous success.
The problem is not that i don't know how to do it, it's that someone else imposes bad materials / practices on me.

The PE said he knows about these hystorical methods / materials and he admits they work.
But the codes don't consider them ...
The largest problem is with codes but mostly with our stupid regulation system.
There's a building approval committee at the local council and there's a person on that committee who puts his signature / seal of approval on the Permit.
This person is not the most technical and if he does not like something, you may have all the coutry's PE's seal of approval, it's worth nothing.
And this council person knows only what code covers - and that's mainly one thing : CONCRETE
Maybe with some small things aside, like wood. BUT it better have concrete written somewhere otherwise you won't get any permit.
Mind you, there's work to remove even stone foundations from codes as they are seen as inappropriate.
This may be true but it's only because nobody learns how to work with stone anymore  
It's a tragic disaster that everyone is doing only concrete since it's "easier to deploy and much better structural", and overall cheaper.
I weep when i hear that.
Any shout about how on earth everything else is still standing is either met with blank faces or with a sharp reply of "they're in bad shape and the next earthquake will finish them off".

Passing this point, even my PE is inclined to go the concrete route since that is at least 90% of what he does.
And remember, he is one of the very few that has a license to work on historic buildings, so he knows a thing or two.
But current code forbids historic buildings from being built new.


Regarding the packed gravel base underneath the foundations, i was surprised at what my PE said.
I suggested him we do this for the below grade part (gravel trench) and on top of it he can put a small concrete beam since that tickles everybody's good feeling.
He said that's the worst possible thing to do.
I was  
He said water will go straight to the bottom of the trench and swell the clay and KABOOM, concrete beam on top will crack.
Or it will freeze and that crack again ...
This won't likely happen if the above structure is heavy - which will counter the uplift force - but with a light structure like mine ...
And i have to put that waterproof pavement around the house, preferably concrete, so water ca never get to the gravel trench ...
Never mind i told him i have seen several places where this don't work ...

I feel like beating some parts of the human specie sometimes ...

I am watching this post with interest as I have a warm soft spot in my heart for grade beams...I think they are a practical alternative.

In some ways I can only by sympathetic to your cause and in other ways I can be empathetic.

Here, for all practical purposes there is no building codes. The town has a Code Enforcement Officer, but the one time I did get a permit, he pulled in at the appointed time, tooted his horn, had me talk through his window and signed the permit. The guy never even got out of his truck. He was there 5 minutes and 3 minutes was spent talking about his basset hound as I had one at the time too. Due to that, last year I never even got a building permit for one of my sheep barns. It is not big at 30 x 50 feet, but visible from the road, and not one person asked me if I had a permit to build it. So in that respect I am sorry that someone of your intellect, deep musings, and wanting to use alternative methods, and can not do as you wish.

But being a farmer I have worked with engineers before and they can be funny. I had the US Department of Agriculture put in a concrete pad for a manure site and they looked at my property...on many acres at a 6% grade, saw a level spot about 30 x 30 feet and said, "You are going to situate it there right?" "Sure", I said, though almost anyone would have known that a level spot next to a house on a grade was most likely the homes septic leach field. Not these guys. So then I am horrified when they say they have to test the soil for proper peculation. They dig a few holes and the State of Maine Soil Engineer for the US Department of Agriculture, Natural Resource Conservation service says, "You need to have a gravel pit here and not a farm." Now let me ask you this, wouldn't you think someone of that caliber of education could tell the difference between gravel that had been tumbled by a glacier, and the sharp, cut rocks of gravel crushed by a jaw and cone crusher? Since it made up the base of my leach field, it was all man-broken rock.

Sometimes I just don't have faith in our regulatory bodies.

And this council person knows only what code covers - and that's mainly one thing : CONCRETE

Unfortunately this is the truth in most municipalities in Canada for us.  No one who stamps permits for municipalités has any knowledge or experience on historic and natural building techniques so they will never approuve something they do not know or understand.  Nor is there any motivation on their part to learn and expand their knowledge as it is so controlled by the construction industry.


We are planning to build a house and will end up with a large concrete foundation (we have to go below 5 feet), unless we choose to build on concrete pillars. Simple fact is, we will never get a building permit to do otherwise.

Maybe things will change as the younger generation that are looking for "green" solutions will one day force building codes to change.


Ionel, do keep us posted as your story progresses.

Great for you Travis.

About 5 years ago we bought a small plot of land (6.5ha) on a hill, starting from the main - but seldom traveled -  road.
We thought some 10-15 years in the future we'll say screw you to the city and move there living off the land with the help of permaculture.
One of the reasons for buying this land was that it's pretty remote and people there don't bother that much about codes.
If there's a very code savvy permit maker, just have the paperwork the way they want it and build the way you want it, no one will check.
Oh, and there are a lot of granite quarries close by.

But now, 3 kids later, living in a tiny flat apartment, at the 4'th (last) level is getting stingy.
And since the far away large property is something long term, and commuting is a PITA, we bought a small (738sqm) plot, 500m from the city sign (we're basically in the city).
The idea is we sell current apartment and build the house with that money.
Of course, being in lion's den has it's (many) disadvantages as i mentioned before.

Michelle, sad but true.
I have accepted this stupid course of events as it can be twisted to have some advantages.
My brain tornado right now is to make this thing not suck (pun intended).
Concrete sucks up water like a sponge and this is unavoidable since concretes that don't suck much are unobtainium.
I must, by design and execution, do things in such a way that this material is not permanently subject to water.
And if it gets wet, this wetness should be only superficial, and there must be provisions for it to dry.
Here enters the gravel / crushed stone / river stone / etc.
This is simple but the way it's layed out might not be so simple.

PS
Now i'm busting my back trying to make those grade beams as few as possible.
Code says grade beams under ANY internal partition wall.
For us those are gonna be most likely drywall ... so it's gonna be a major bummer to put a bazillion grade beams in there ...
All that's gonna be double tough as the wife has designed the interior spacing in such a way to maximize space usagethat the construction axes don't go straight from one end to the other ...
Great for  but agony for someone trying to not fill everything up with the grey stuff.
I wouldn't bother but the codes say the grade beams should come upto floor level.
That's not a problem if you put a continuous concrete slab above, which i definitely never want to do.
But if you want to do some earthen or wooden floors with insulation underneath and the darn grade beam comes up right thru the middle of the livingroom or bathroom ... well, screw the insulation ... we have a glorious sill to trip over and a nice thermal bridge.

Oh, the joys of trying to do things right.

PS2
My highest irritation is about the fact that i can only speak with people at the top, of the highest technical knowledge and understanding.
Trying at any lower level is just an exercise in frustration / futility / mad cow disease ...
Problem with these top people is they have some interesting personalities (i can manage that) but are extremely short on time.
If i could get my PE exclusively for 2-3 hours i'd touch all subjects i care and the thing will be done.
But as it stands right now, i can get 20 mins, maybe half hour of half babbling and spoon advancement ... not nice ...

Many years ago I lived high up on the moors in the North of England a friend nearby had a very old house ( 1660 ish ) thick feildstone walls my house at the time was a more modern 1815 . Someone had put a concrete floor in . The house used to be a pub and we could see stones that looked like lintels on the outside  about 15cm above the ground level . mmm cellars we thought !
So we dug a deep hole one sunday morning ( powered by beer ) what did we find?  dirt nothing but dirt and clay no cellars but also no foundation!
My now very worried friend talked to an architect on the monday first thing who assured him this was the way it was built and since it was 300 years plus and still standing it  was unlikely to be going anywhere soon.

ionel ... you are awesome. it s hurtful to read the stress that the coding people cause. i hope, you ll find a solution.

have you thought about french drains at the bottom of these gravel trenches?

David, common knowledge.
I have talked to architects saying it's much better from all pov the way i want to do it (from traditional ways) but code forbids that.
My PE, one of the best available, is of the same opinion (although he has his own quirks), but that's not the issue.
The best people around know this but they don't want to move a finger against code.
Or, they spec as you wish but warn you're not gonna pass local permit aproval.
Or, they spec according to code and you do it your way (if the inspectors don't find out, else you're in a orld of hurt).

Tobias, french drains is if i put a perforated tube on the bottom of my trenches.
It's just some more plastic which will make water move faster.
It'll work without the plastic pipe, just a tad slower.

Hi everybody.

I'm advancing slowly with the thinking on this foundation system.
The pads are easy, just dig a hole and pour the darn thing in.

The ways to build the stem walls are plenty, each with pros and cons.
But the surprising fact is the overall costs are the same.
Some methods cost less in materials and less in labor and some others cost less on materials and more on labor.
Some methods offer stem wall thermal insulation while some others do not.
Let me give you some examples of what i'm thinking:

Ways to do it	Pros	Cons
Pay someone else to make the forms	Not much work for me except supervising	Insulation at an additional cost both in materials and labor
Make the forms myself	Maybe a little cheaper ?	A lot of work and no insulation
Make the forms myself and include some insulation	Has insulation	A little more costly and labor intensive
Use some predefined insulative forms like ICF	Forms are also permanent insulation, very easy to set up	Frickin' sytofoam with all it's disadvantages
Make my own insulative forms	Forms are the Insulation	More labor intensive

After researching all these, remember the total costs are similar for each of the above, i decided the best option is the last one.
Since i don't fancy using EPS (expanded polystirene) because many factors including the dubious affair of making it rodent proof, i better find some rodent proof insulation.
And guess what, there is some.
I could use AAC (autoclaved aerated concrete) blocks or big hollow brick blocks.
I chose the hollow bricks since they are just a tad more expensive but are not so sensitive to water and have 5 times the compression resistance.

So now, i just have to make a small double wall out of these bricks, temporarily reinforce it to withstand the pouring and that's it.
All ice and dandy, there's just one catch.
And we're coming back to our beloved concrete again.
This thing is hygroscopic even when fully cured.
That means it will be "wet" and i don't know how well the bricks will behave in this situation.
As a plus, the grade beams don't directly contact the soils, they are on top of a gravel layer.
But the concrete blocks are in direct contact and could expose the beams to wetness.
I could try and use a layer of gravel alround the blocks but will have to fight hard the PE.

So, do you have any experience with bricks, hollow or not, sitting in contact with concrete ?
I really  want to know if there's some concern in using them like this.
I will try to talk to the brick manufacturer but i have the feeling he won't be very helpful.

This is the brick i want to use for outside:
Porotherm 25-29 Th Light
And this one for the inside:
Porotherm 11,5 N+F

what about moisture barrier on top of these blocks? builders here use tarpaper. you could use a paint-thing. or foil. or a sheet of stainless metal.

Hi Tobias.

Since i will be forced to use friggin' concrete, a moisture barrier on top of the stem wall is absolutely necessary, otherwise the wooden sill will not last.
Traditionally, this barrier was bitumen impregnated cardboard - or as you said, tarpaper.
This will span across the whole top, from the exterior hollow brick -> grade beam / stem wall -> interior hollow brick.

It's not this moisture that i'm worried about.
It's the one passing from the concrete into the bricks.
The bricks are hollow and can facilitate airflow, with a little care.
The bottom will sit on gravel and the top will be closed but not completely, enough that water vapor can escape.
Air flow means a chance for potential wet things to get dry.

I'm worried about lifespan of wet brick (if indeed it will be wet - this i don't know and would like to find out) and thermal transfer coefficient.
Wet things are not good insulators.
And wet things get destroyed on freeze / thaw cycles.

And if using hollow bricks won't serve as insulation for long as they will be disintegrated, then why use them in the first place ?
Might as well use ICF (insulated concrete forms).
This is something i'm trying to figure out.

i meant on top of the pads, not the stemwall, sorry

In theory it should work.

Problem is, the grade beams are connected to the pads.
There is 4 x 12mm rebar encased in the pads and sticking out into the grade beams, connecting with beam rebar..
The connection between pad and grade beam is called a cold joint since the 2 were done at different times and therefore not perfect.
Water can enter thru that joint and cause damage, even more so if there's a moisture barrier there, as i will be more likely imperfect connection.
Maybe a combination tarpaper layed with liquid bitumen using some torch to get a good grip.

But it's all going to disintegrate some time after 50 years so who cares.
I'll put this in the plans, maybe the PE will like it , who knows.

hm... what options are there to waterproof concrete? liquid acryl stuff (some kind of primer)? there are special products to prevent concrete (or brick walls) from wicking moisture.

i doubt that much moisture will wick up through the rebar. probably near to nothing. probably you could coat the rebar with anti-rusting-paint-stuff. but i don t think that you would need to.

i think that most of the strength of that joint comes from the embedded rebar, not from the two concrete-surfaces bonding with each other. but your engineer will tell you...

There's no such thing as waterproof concrete.
There are grades more or less spongy, that's it.

The damage i was referring to is to the rebar, sorry for not being clear enough.
Theoretically, concrete embedded rebar is protected, even if it's wet, due to the high alcalinity.
Theoretically because water is never clean, it always has some salts that start corroding rebar which rusts and spalls, increases volume therefore cracking the concrete which lets even more water with salts in ... ad nauseam.

So, the only thing tying the grade beam to the pads is the rebar, that is for horizontal, aka earthquke, stresses.
And the current PE's don't  quite grasp the notion, as expanded in the original raised earth foundations, that buildings JUST SIT on they're foundations by weight alone.
And in they're minds, if this rebar is gone, by rusting for example, then you have a compromised foundation, which imho is total nonsense.

stainless-steel rebar

or titanium


ok. coating rebar should be good enough.

is there any way to waterproof the pads from the outside? like pouring them into a waterproof rubber-bag? mylar? even simple plastic sheets could do, because they re dug in, so they re protected from degradation through UV-sunlight.
or dig barrels in and pour the pads into that. or cut off IBCs.

or sit the pads on gravel and put frenchpipe below the pads. that should make engineers happy.

but still i don t think that much might wick up, when you have moisture barrier on top of the pads. even if, you ll have ventillation around the stem walls.

If you have enough gravel for good drainage, you won't get liquid water in/on the bricks or grade beam outside of maybe big floods. A vapor barrier under the bricks and grade beam will keep most of it dry, and vapor that is not airborne is proportional to conductive area. If you have a tiny gap in the barrier, you will get a tiny bit of vapor. Liquid water or airborne vapor are different, of course, and a tiny gap can be fatal.

I once lived in an old house with a thin concrete basement floor poured directly on dirt. It was always moist. There were broken spots in the floor, and I patched one with concrete and put plastic under it. That spot stayed dry while the floor around it was damp.

When dealing with code officials, I've found making THEM responsible for the decisions they make works wonders.

Officials can grant a "variance" to a particular code.  Codes are NOT "infallible" and are often ignored, or variance granted by officials.

In some instances, different departments will have conflicting codes about the SAME THING... and there is no way to adhere to BOTh codes... so one department basically "ignores" their own code.  If they can ignore one code, they can ignore others.

Case in point:  In LA County, the Fire Department Code requires hillside plantings to be spaced far apart to prevent fires from spreading.  The Grading Department code requires hillside planting closer to together to prevent erosion.  It is literally impossible to adhere to BOTH codes.  So the grading department ignores their own code!  These type of discrepancies Can be used as arguments against the code... But you need to search for them to find them.  

Officials main fear is that by allowing something that's not conventional, and if it fails, They will be sued for it.

HOWEVER, if it's made clear to them that if they persist in forcing their codes on you, while refusing to approve older methods that have worked for hundreds of years are still working, that they will be sued if THEIR method fails, they often will reconsider.

It's usually about liability...

Then there are instances with officials who are just ass%$^#s.  These are power hungry beurocrats who just enjoy screwing with people.  THOSE guys you need to battle HARD.  Go over their heads.  Put EVERYTHING in writing so there is a paper trail, and MAKE SURE THEY KNOW that.  They often will want to "talk" to you, and have "meetings".  This is so there is NO PAPER TRAIL, and they can later claim whatever they want. Your best bet when dealing with those types is to simply say the following:

"at the advice of my attorney, everything needs to be done in writing so there is a clear record of what's been decided, approved or not approved, in the event we have a legal matter later."

When put on notice that you are going to hold them accountable for EVERY Action, they usually leave you alone.

I've dealt with this repeatedly in dealing with LA County, and LA city officials, and LA has some of the most difficult codes in the WORLD.  Yet I've managed to get variances for all sorts of stuff, and/or they've left me alone.  

Variances can also be granted when the construction technique meets the "spirit of the code".

For example, when I built my underground house. The code required insulation in the attic.  However, there was no attic, AND the energy calculations showed the house would use 80% less energy for cooling and heating over a conventional above ground house.  Since my house met the "spirit" of the code, they easily waived the insulation requirement.  That was one of at least half a dozen variances they granted.  Now, my plan checker, who was a total asshat, and is a story in and of himself, refused to grant a variance, and even insisted variances don't exist.  The second I went over his head, his boss stepped in, and granted every variance I asked for.    

There's also the persistence factor.  if you keep going back, and battling them on everything, they can't get anything else done... there comes a point where they just want to get rid of you, and will sometimes just approve things to get rid of you.

The key is to be polite, but VERY FIRM in how you deal with them.  Every once in awhile, letting them have it can help too.  LOL.  

One time, I went in for a slight plan change on plans that had already been approved.  They had previously told me what I wanted to do was no big deal.  So we modified the plans, then I brought them in.  The same guy who told me it could be done "over the counter" in about 5 minutes a month before, now insisted he didn't remember telling me that, and that I had to basically start the entire process over, and re-pay all the fees.  (THOUSANDS of dollars).  I had a slight meltdown, and told him to go in the back and get his supervisor out front to discuss this.  He asked "which one?"  I told him "all of them.  Bring EVERY single supervisor back there out front.  you tell them I'm out here, and we need to discuss this."  (We had had issues before, and they knew me by this point.)  

The guy disappeared in the back, came back 15 minutes later, and handed me my plans and said, "you're all set.  Everything is approved."

So basically one of two things happened:

1) They lied, no "recheck" was needed, and were simply trying to collect more fees from me.  (Which I've seen them do.)

or

2) They knew they were going to have a huge battle on their hands with me, didn't want to deal with it, and instead just signed off on something they shouldn't have.  

Neither reason is acceptable, but in the end, I got what I needed done.  

This is why my next place will be somewhere with minimal to no codes whatsoever.  

Let me also add this.

Officials HAVE to consider and look at alternative methods.  If they refuse, get a lawyer to write a strongly worded letter.  

Also, the more people you've had sign off on something, the harder it is for someone to deny it.  So the "guy who isn't technical and won't sign something even if every PE approves it" won't have a leg to stand on.

Also, when you are dealing with this guys, get their full names, proper spelling, badge numbers, etc.  Make it clear you are keeping a record of them, and writing everything down in detail.  This can also work wonders.

I've had officials who were reluctant to give me their full names, I persisted, they asked, "why do you need my full name?"  My reply:  "for the record, and because my attorney told me to get that info in case we need to serve you with a subpoena or name you in the lawsuit your actions are likely going to result in."  Suddenly, things were magically approved.

Knowing the codes is also a good thing.  I've repeatedly had officials misquote a code, (or blatantly lie about it), but I had done my homework, and knew the code.  Sometimes, the codes are vague and ambiguous, meaning easy to challenge.  Other times, the WRITING of the actual code leaves much open to interpretation... and if it does, you can capitalize on that.  

In a nutshell, often times when dealing with these bureaucrats, you need to be a bit of a dick.  Let them know you're not giving up, you know your rights, you know your stuff, and you know the code, and will fight them to the end.

good luck!  

Thanks all for chiming in.

Tobias, you had a good idea with the membrane between pads and grade beam, one i haven't thought about but it's worth insisting on.
There's no point in waterproofing the pads from outside using plastic membrane or tarpaper because at some point water will get in but won't be able to get out.
The only solution is drainage.
Gravel beneath and around the pads.
Beneath is easier from an execution pov but will have fights with PE.
Around is tougher to execute and more expensive and at this point i really don't care about the PE.

So putting that bitumen tarpaper as you said will let me not care if the pads are soaking wet.

Glenn, spot on.
I plan to put a hefty layer of gravel underneath them beams and around, a little above grade.
So whatever water gets there will get away in an instant.

Eddie, my dear fella', you had a full experience there.
The things over here seem pretty simple (but wrong on so many levels none the less).
1. Structural engineers are liable to PRISON if they're structure fails under 50 years under normal, estimated, stresses.
This is national law.
That's why they oversize everything.
2. Codes are minimal and mainly center around concrete for foundations.
Each jurisdiction can decide to accept only a part of what codes specify or be more strict about it and this is sometimes the case.
Permit signers are not liable for anything and a direct fight with them might not be a good idea.
There are other ways, fortunately or unfortunately.

Ionel Catanescu wrote:BUT it better have concrete written somewhere otherwise you won't get any permit.
Mind you, there's work to remove even stone foundations from codes as they are seen as inappropriate.
This may be true but it's only because nobody learns how to work with stone anymore  

[small slightly OT rant] I imagine it may have less to do with a lack of training, and more to do with who the friends are of the people that write the laws and building codes. Call me suspicious, but I would bet that if you check among them, you might find big manufacturers of Portland Cement, and big builders and building supply (rebar, etc.) manufacturers and merchants, who live well by charging high prices for their "modern" products, in every project, all over the country.  

It is fairly standard procedure in "modern" societies the world over now to develop and use contacts in government to ban those terrible "old," "primitive" methods that have been in use and working well for hundreds or thousands of years, that do not have the virtue of costing so much, and of course, being exclusively available for sale from these big companies and their friends. (Compare: Pharma/herbal medicine, dry stack/reinforced concrete, natural gas/rocket stoves...)

High cost for consumers, to the politician = "a boost to the economy and GDP" = doing things well.  

Sustainability or the natural living world famously have never entered into the core of mainstream economic calculations. Mainstream "modern" economics literally assumes nature/resources to be unlimited, "natural capital" (the stuff nature gives us) to be worth zero, and "externalities" or waste products to magically disappear. Thus the whole field of ecological economics trying to counteract this insanity. [/small slightly OT rant]

Anyway, best of luck in convincing the builders and bureaucrats to make exceptions for well thought-out small projects such as your own. In many areas, for instance, small farmers have been able to get exceptions to sanitary and marketing regulations to allow them to sell value-added products direct to consumers. It would be great to get the same kind of movement going in green construction!

Dave, absolutely as you said.

What i meant to say is that stone foundations are actually very good in the hands of stone masons, the real ones.
But these real ones are dead or dying or just a handful left in the country or selling they're work for an arm and a leg.
Every once in a while i hear about a tv show with "the last stonemason in the country", a guy carving and laying stone that should have been dead 100 years ago.
needless to say, even though we speak the same language, his soul and speech seem very foreign today, but very true.

The other stonemasons (the patchers) have no idea what stone is about.
Just cover it in cement mortar to glue things up and it will be ok.
Code enforces this unfortunately.

So, if one of these patch'up stonemasons does your stone foundation, you betcha it's gonna be inappropriate.
And almost nobody learns the old ways - therefore code - very conveniently - forbids these practices.

I'll give you a rough translation of what code says about stone foundations (just a tiny space) - the part that is on it's way out:
"Stone can also be employed where it is available, in the mountain ranges of the country"
So, it's used only on account of local availability, nothing on it's virtues.
It's been a long time since i've last heard of someone in the mountains building with stone ... even if it's in, on and around the construction site.
ornamental use, yeah, that's another story, but structural ?

Hi guys and gals.

I'm back from my incredibly crazy brainstorming without a clear answer, just more possibilities / questions.

I've stopped now on the topic of floor insulation.
IS this a real thing or just modern hysteria ?
I mean, old buildings did not have insulated floors while most modern ones do ...
I do intend to use a RMH for space heating but it would be foolish of me to not put a dime aside and install appropriate tubing for hydronic heating.
Considering the floor will be a form of stabilized earth (clay/lime/pozzolan variations like rammed earth or tataki), that should be very simple to do.
But if i heat the floor and the subfloor (mostly gravel) is cold (which will be during winter since it's coupled to the ground), i'll lose all heat by conduction.

So here comes the insulation into play.
It has to have 2 qualities:
1. be as insulative as possible
2. not break apart when tamping the floor into place

There are some choices available:
- aircrete / aerated autoclaved concrete
- mineral wool
- hollow brick on it's side
- EPS

Now, aircrete has potential moisture issues underground and not much load bearing but immune to rodents.
Mineral wool has great insulation and not much rodent issues but no load bearing, except the highly expensive types which have a "little" but not enough.
So i'm left with only 2 contenders.

Hollow brick has excellent load bearing capacity and rodent resistance but modest insulation and price is not great either.
EPS has excellent insulation and price, has reasonable load bearing (the EPS200 types at least) but rodent damage is assured unless special precautions are taken.

So, comparison on price / insulation values.
For the same price, hollow brick 30cm thick will have a u-value of 0.47 W/sqm*K while EPS (20cm of EPS100 and 10cm of EPS200 on top) will have a u-value of 0.127 W/sqm*K
SO, for the same price, EPS has 3.7 times less losses or is 3.7 times more insulative.

But EPS is friggin' EPS.
I hate it when the the "apparent" best solution is a "toxic", pest ridden one.
I would have loved for this 3 year old thread to have detailed more about usages such of mine but it deviated into fire burning toxicity which won't be possible in my scenario.

So, hollow brick is more expensive, less insulative with almost no chance of rodent damage - high initial investment, higher heating costs due to losses.
EPS is cheaper (relatively) with better insulation - lower initial investment and lower heating costs due to lower losses.
EPS caveat : to protect it, a stainless steel mesh should be placed as a shield around the foundation perimeter or as a netting directly under the EPS, and this has pretty steep prices raising a lot the initial investment.

So, after the new year's celebrations end, maybe someone will have an enlightened eye to give me a bit of advice on something i haven't thought about.

Happy new year,
hopefully.

my brother-in-law used a kind of foamed glass for the floor. he s renovating a maybe 200 year old house. he used that in the cellar.
this product comes in chunks like charcoal. it feels lightweight, like big pieces of perlite.
if i remember correctly, it should be very insulation and non-wicking.

i m not sure if any kind of pest would like to dig in there. if you touch that stuff it feels yuuuuuuuuuuuuuck. it leaves super fine glass dust on the skin. yuck.

EDIT: wikipedia says its pest-resistant. it can be used under concrete slab foundations, it should handle the pressure of your setup. and it´s made from recycled glass.

Hey Tobias, glad your brother-in-law found this product and (could) use  it.
It's a great product for underground, heavy duty work.
It has the same thermal properties as EPS / rock wool but is load bearing, much more than even XPS.
It's approaching concretes in load bearing and, as you said, rodent proof.

It has only one MAJOR problem.
It is VERY expensive.
5 times the price of XPS and 7 times the price of EPS200
If i were to use EPS200 (highest grade of EPS) it would cost me cca 2000 Euro / $ for the whole house.
I don't even want to think of multiplying that by 7 ...

We have a saying around here : "Money don't grow on trees".
We're on a permaculture forum and know that is not true, money does grow on trees, albeit in a different form.
I just haven't even planted those trees ...