Cold climate foundation choices?

Hi everyone,

Glad I joined this forum, its great to swap info with like minded people.

I am designing my future cottage and will have to deal with codes around montreal. I am looking into foundations at the moment for my strawbale infill. I remember visiting a building site 5 years ago when I was studying carpentry construction that used ICF's.

The research that I have done it seems for code I could do a frost protected shallow foundation FPSF with ICF's.  I am trying to find a design that will allow for an independant slab (an earthern floor) rather than a concrete one that is connected. A plan showing a concrete slab is fine aslong as its independant and not monolithic attached to foundation wall.Anyone seen anything or worked with them??

It needs to work for a cottage that may or may not be heated so the ones I ve seen insulate underneath the whole thing the same as a garage.

I will attach a rough picture of what I am thinking. Ok I know the ICF's are 8" or so and a strawbale is 18" plus plaster and in my pic they are the same thickness, so sorry will redraw after a few replies . Also not sure about the floor layers yet and the heights etc but lets start with the basic concept first and fine tune the drawing later.

If you have any input for code approved I would be grateful so no earthbag or rammed tire ideas. I love them too but can't do them yet, maybe 2012 will happen, might be the break the planet needs and all of use can ram what ever we please. Sounds kinky eh? Will it is dirty!

Cheers everyone
Enviroman

While overall it looks for the most part okay, what you're doing with the insulation is unconventional.

1.What's the purpose of having the insulation slope away at an undecided angle for 4'?
*If it's to drain water away there are better methods, If it's to insulate more it seems a bit useless to waste the material going sideways. You'd get more constant temperatures going straight down.

There's also one major factor that may change your detail.
-Water Table: If you building is anywhere near the water table you will need a Sump with a perforated drain pipe around the exterior of your stem wall. Your other more passive alternative would involve setting up fantastic drainage and accepting that during heavy rains you might flood a bit. If you are near the water table I would also suggest you have a concrete foundation instead of compressed earth on sand.

A free online resource on common construction methods I found a while ago is here. They don't discuss straw bale, but it does go over the most common american foundation details for residential construction.
http://www.engext.ksu.edu/henergy/envelope/builderguide.pdf

Three points on your foundation. 1.  On the sloped insulation running away from the foundation.   This is a totally legitimate practice in areas with extreme winter conditions. There are many areas of heavy clay soil on the Canadian prairies where the ground can freeze to a depth of 6 feet or more. Frost heaving has destroyed many well-built concrete foundations as the moist clay expands with thousands of tons pressure. This insulation limits the depth of the winter freeze and the unfrozen clay surrounding the house becomes a buffer for all of this frost heave pressure. Very common around Lake Winnipeg and in other cold and moist locales. Further north in the Yukon and Northwest Territories there is a problem with permafrost melting under homes built upon it. Some people insulate the soil seasonally. They allow a very deep freeze in the winter and then spread the foam in the spring so that their homes fragile support on frozen ground does not thaw out. These homes are generally built on pilings or up on blocks. Slab on grade is uncommon.

  2.   You might want to examine rubble trench foundations. Although they are uncommon in Québec residential construction they are definitely used for commercial buildings which are much heavier. Many concrete block buildings like gas stations and grocery stores are built on these foundations. Frank Lloyd Wright used them extensively. Some of the heaviest castles in Europe rest upon rubble trench. Rubble trench gives excellent drainage and uses less concrete since you only need a grade beam. If your building inspector is at all knowledgeable he has heard of this.

   3.   Much of Québec has high levels of radon gas naturally occurring particularly in areas underlain with granite. Next to cigarette smoking this is one of the leading causes of lung cancers on the Canadian Shield. Environment Canada or your local building department will have information on testing and remedial action. Usually this means some good quality vapor barrier under your gravel plus some PVC pipe vents. I've heard of government grants for this portion of the work. If they exist in your area you may find that your excavation is subsidized.

Thanks ilchianti and Dale for your replies already. Yeah the four foot skirt is normal for these foundations and the slope too but most drawings show them horizontal yet in practice its not. Was trying to be as accurate as poss. lol. I redrew my foundation adding in footings and drainage, also a toe up for the bale width difference, can also chase wires through it, one option as I want bales off the floor.

Dale that permafrost thing, got me upset all the trapped methane is coming out, its scary stuff, those poor people with their buildings up their, I would be moving asap. I like the rubble trench but worried about code. But say I could, how would you insulate it, similar to the ICF??

My other question now is do I insulate under the footings too? I  or above the toe up and I guess I should start talking to some ICF companies, any suggestions?

Radon gas, I remember when I took my trade at college in carpentry construction something about having to include a pipe for the radon gas to vent think it ran from the ground all the way out of the roof. Yeah it can kill too if you don't. For the water table issue, I plan on catching the rainwater to harvest and will have 4 ft over hangs, a clay soil, gravel, french drain and maybe the insulation will help as you say for run off, another benefit, cool!

It is interesting to see your detail developing, I do quite a bit of work in the Peak District in the UK where we often have radon problems. If the survey shows high levels we usually put in a radon sump and vent pipes below the damp proof membrane. Often the membrane is a heavy gauge too. If we find levels are low or the ground is just showing CO2 reading we will use a 2000 gauge DPM if the levels and gas flow rates are high we tend to involve specialist companies and get a warranty on the products & system for peace of mind.

I am not familiar with the codes and practice in your part of the world, so forgive me if I get something mixed up. Is your straw bale wall going to take the weight of your roof or are you planning to have a frame work to do this. Looking at your detail the straw bale seems to be only partially bearing on the supporting wall, just a thought but I would be concerned about the stability or localised crushing if this wall is taking the roof load.

The one straw bale I saw built was framed like the following .pdf shows on page 29 & 30.

http://www.ecohabitar.org/PDF/strawbalebuildinguide.pdf

Generally in the United States Straw bale is purely insulation material, providing some additional bracing to the structural frame as the posts and straw bale help counteract each others' bending and settling.

In the cob house I saw put up they didn't plaster the exterior but enclosed it in corrugated panels that they sealed at the top and bottom, so they could swap out the bales every decade to reduce possible problems due to decomp, mold, etc...

Hi there,

Thanks for the replies. Yeah I am carpenter by trade and I will be building with wood frame construction. So the straw will be infill. The peak district wow you are lucky I am originally from London been here 12 years or so now. Miss it now, lol.

The radon gas might make a good post on the forum, I will follow our code for that but my issue here is my foundation design and the ICF insulation stuff etc. Rubble trench I like but still have to insulate so any ideas on that would give me another option. Just need to insulate under the slab and tie it in etc. Just not sure about under the footings?

Thanks for the link ilchianti it was a good read, took a few bits such as the hazle in the bales rather than rebar which can cause moisture in the walls. Glad to hear they are in the UK too. I know cob is and lime plaster for the rain. I will try clay plaster with good overhangs.

When It comes to construction details I have a digital library that's almost too large. I'm trained as an Intern Architect and will hopefully in a few years have my architect's licence. I'm unfortunately not too versed in construction in construction with radon prevention in mind. Super-Insulated buildings on the other hand, I'm familiar with.

The following pdf shows the simplest way to get a complete slab insulation.

http://www.google.com/url?sa=t&source=web&cd=5&ved=0CD4QFjAE&url=http%3A%2F%2Fbouldermountainresources.org%2Fdownloads%2FSuper-Insulated-Slab-Foundations.pdf&rct=j&q=superinsulated%20slab&ei=MhuJTq_1IOeusQKyk7mMDg&usg=AFQjCNGGiC_nGbhJZwU_7L5c9Kw04_gwOA&cad=rja


Unfortunately I don't know any good ways of insulating the slab that doesn't involve foam insulation. The other alternative is always just going the earthship way and not directly insulating the slab.

Thanks a lot ilchianti for the great link to Branch river and the perimeter grade beam foundation. Wow okay so EPS way better XPS for the enviromental manufacturing issue. Those guys use 6 inch of form under the slab, WOW! I thought the info was great, I will start comparing with other ICF company's and then post my findings later.  I like the idea of horizontal insulation for simplicity and then the perimeter beam for less concrete. Not sure about the width 20 inch is very wide and I think I recall some being only 6 inch wide of concrete then maybe 12 inch total with insulation.

For the earth floor I have done some research and I really like it for owner builder aspect, no concrete, thermal mass, beauty, simplicity etc.  I wish I could go completely natural but its not realistic for building around here. Using any foam or concrete is a hard one to take for an enviromentalist but at the moment this FPSF with just a perimeter on insulation over a 12 inch gravel base sounds a serious contender. It also would keep my strawbale up, think 9" to 18 " is suggested so was think two 16 " one below grade and one above with extra insulation around the Toe up for the extra width of the bale.

I think your comment on water table would be picked up in a survey. What about about if its bedrock? How do you deal with foundations then. I think thats cool you are getting you license, you are an assest to this forum. Thanks for any links. Looking at a site in two days for practicing some ideas with straw and mud walls. Land is a friends who said go play! Doing a soil test first to see what I got. Will be posting more very soon.

Cheers mate

If you're directly on bedrock you most likely would put the building up on piers drilled several feet into the bedrock and forget making a slab.

If you really wanted a slab on bedrock you would probably end up spending wayyyyy to much just having the ground leveled/dug.

The only true positives of building on bedrock is the fact that if you don't have to worry about bearing capacities and landslides.

Nice to see you have settled in well from a life in London Enviroman & thanks for the links ilchianti, I find fascinating to see how detailing differs from place to place.

The only non foam/concrete insulated floors I have come across are Limecrete and Hempcrete, I have not detailed these as yet but I done a little reading around them in the past. I do know that certainly Limecrete is prone to suffering frost damage if the cold gets to it before it has set, so it may not work too well (or for that matter even be available) where you are.

With regard to insulating a solid floor: one project near me used 300mm of foam below a thick slab, with the south facing glazing and no carpets to act as a barrier it worked brilliantly as a heat sink and heats the homes all year. Perhaps this is something your earth floor could give you.

You might look up earth tubes and see what they suggest.  Here is one link
https://www.thenaturalhome.com/earthtube.htm  They are very much aware of the effect wet soil has on foundations  and suggest that sometimes it is helpful to extend  barriers up to 20 feet out from foundations, suggesting several alternating layers of 6 inches of straw and heavy plastic. Earth Tubes  is the system used by the Citrus In the Snow guy in Nebraska, though I have no idea what he used to insulate his system.

Even if you aren't intending to use Earth Tubes, what those who do use to max their effect might be helpful to consider. Dry earth won't bounce your foundation and fireplace around like wet earth will. Nor suck out the heat from your house. Hot air rising and cold air falling is all very well, but temperatures try to equalize. Keeping the soil dry under and around your house is a very good way to minimize heat transfer to the ground.

I dont have the final answer yet but for bedrock I guess piers is best.

For normal conditions if I did ICFs I think insulation under the slab is a must, also extending out 2 feet around the perimeter with a graded slope. French drain and at least 6 inches of gravel under the foam. I would also run the foam under the footing but not sure if I need a wide footing.

I want to do an earthern floor and I know foam isnt green but the EPS seems better than the XPS foam. I need to find some companies that make them and send them my design. Other ideas wont pass code and dont insulate well, or you huge amounts of wood flooring which still needs insulation.

I did think that once the ICF has been filled with concrete that I should remove the foam from the inside and add it to the outside, it doesnt make sense to leave the inside insulated as the concrete part should be part of the envelope on the inside. I am talking about the radiant heat effect and using the thermal mass of the ICF. However code may not permit and also may prove to be akward to actually do.

Anyway  if anyone wants me to draw a new pic of my update then let me know, I need inspiring. Thanks for all the input so far.

Enviroman,
I am interested in how the house was built? Did you start it? I have some of your concerns, but I am not on bedrock. I have the complication of wanting to build where every 15 years or so this place floods for a short time maybe 4 hours with a foot of moving water ( having jumped the creek up hill). Until I discovered this sight I was going to build up with fill, but I understand that that is unstable now. As I see it I have two options, build a foundation that the water can pass through or try to make it impervious. So far I have only come up with this idea that I crudely sketched.

Enviroman,
I am interested in how the house was built? Did you start it?
I have some of your concerns, including a cold and somewhat damp climate(just south of fingerlakes area of NY ) but I am not on bedrock. I have the complication of wanting to build where every 15 years or so this place floods for a short time maybe 4 hours with a foot of moving water ( having jumped the creek up hill). Until I discovered this web sight I was going to build up with fill, but I understand that that is unstable now. As I see it I have two options, build a foundation that the water can pass through or try to make it impervious. So far I have only come up with this idea that I crudely sketched.
I can't seem to upload it maybe because it's a jpeg?
Well I'll try to describe it in words. First a rubble trench, with drain to daylight. Then Gabion basket foundation wall 2 .5 feet. One half a foot bellow grade 2 feet above grade. Inside where there will be floor, fill with rubble.
On top of the Gabion basket wall insulated concrete. The inside rubble would come up a few inches above the baskets, then insulation then an earth floor. My thinking is that the rubble filled foundation will let the water pass through but be stabilized by the gabion baskets and the mass of the rubble. What do you think? What does anyone think? Will it work? Thanks for any and all imput.

I forgot to add that on top of the insulated concrete there would of course be a cob/straw bale wall.

We have a floating slab sitting on insulation on crushed stone on ledge and keyed to the ledge. We're in the mountains of northern Vermont. Our cottage then sits on the slab.

http://SugarMtnFarm.com/cottage