Northern Alberta foundation ideas?

sirmike68 · January 10, 2008, 04:48:11 PM

I am in the planning stages of a hunting cabin on my newly purchased property in northern Alberta. I was thinking something about 14 x 24 like the Nash cabin. The planned building area sits on about a 2 acre "high" spot surrounded by muskeggy water logged soil. I think the area is fairly high in clay because the few holes I have dug have been extremely hard to do and remarkably dry but then I only dug down a foot. The area civil engineer said the frost line can be up to 9 feet down. I can not get any heavy equipment into the area and everything will be done by hand or whatever my generator can run. So digging piles that deep are out of the question. From your guys expierence what is the best foundation for my situation?

Redoverfarm · January 10, 2008, 05:36:20 PM

There has been simlar topics posted on various threads with your frost line problem. I don't recall exactly which ones they were mentioned in but if you have a little extra time search throiugh some recent post and you may come up with one or two. Or maybe someone's memory is better than mine and they will recall which ones and direct you there. Is it not icing up time there when season is in. I would hate to get caught there for the winter if you wasn't prepared.

January 10, 2008, 05:36:43 PM

Maybe an adjustable one on well drained gravel - sloped trenches of gravel drained to daylight if necessary to minimize frost heave would be one of my ideas.

Are there other buildings in the area to check and see how they have survived?

Welcome to the forum.

bobtheengineer · January 11, 2008, 04:56:02 PM

If there isn't any plumbing running to/from it, or any rigid electrical, you might want to consider building the building and mounting it on timber skids. You could dig a couple of trenches for the skids and put gravel in em, and bring it up to level grade and build from there. It will heave and swell a bit, with frost heave, but it shouldn't be anything too large, that it would upset the building.

sirmike68 · January 11, 2008, 07:44:23 PM

No plumbing but I will wire it so a generator could power everything in the cabin. If I used something like railroad ties and built this thing on a skid how much frost heaving can I expect? I wouldn't think it would be too much, maybe if a guy could make the skid foundation rigid enough the building would not twist and flex enought to cause problems.

January 11, 2008, 07:52:01 PM

How much depends on your conditions. On a well drained rock bed should help. Adjustable beam or post mounts would be nice so you may not have to jack it op if things shift -- just readjust the jack bolts.

hnash53 · January 16, 2008, 09:40:42 PM

I'm the "Nash" of the Nash cabin. The key is to prevent your footings from getting wet. That is done by providing good drainage. I dug down below any organic material, about 6-10 inches, packed it with gravel, preferably crushed rock. Then you need to insulate the footing in some way to keep the ground from freezing around and underneath your footing. Scandinavians have done this for years. A search on this forum should provide some links for you. I layed down 4'x4' tarp material around my footing to prevent water from getting into my footing. Then I insulated it with wood chips piled up around my concrete blocks. Look closely at the pics on the website here. The wood chips retard air flow and prevent the cold from entering the ground, basically insulating the ground from freezing.
This is similar to what people do to keep their potatoes from freezing during the winter. They pile grass clippings on the ground above the potatoes and it works. I saw this in Montana where it gets cold.
It's worked for me since 2001. I've had no settling around the perimeter, all the windows and doors still open and close as they did the day they were installed.
Best wishes in Alberta!!

lonelytree · January 16, 2008, 10:15:07 PM

Helical piers are out, $1000 each.

Piles can frost jack unless VERY deep. It would require heavy equipment anyways.

Here is my current plan. Remove all vegetative matter from the pier area ONLY. Pour a nice cement pad. Put a couple layers of cement blocks together and fill with cement. Put an adjustable jack on it. Something like this:

I am building in semicontinuous fermafrost in Alaska.

Redoverfarm · January 17, 2008, 08:00:57 AM

lonelytree sounds like a good plan. To go one better stop by a camper trailer supply or dealer and pick up a couple of levels to affix to the sides of the structure. This will allow easy intermitent inspection of the tilt (if any) then you can adjust it. Just install them at the onset of your completed (level) framing. Yes a 4' level would work just as well but these will always be where you put them and you will not have to go find it.

January 17, 2008, 09:34:05 PM

I was also told to make the floor joist area as solid as possible. If a corner drops, the house should have minimal twist.

I am now trying to find 1" or better threaded rod "cheap"

sirmike68 · January 18, 2008, 01:01:25 PM

THX for the input guys. I still can't get my head around "insulated footings." How can one stop anything from freezing if the temperature gets as low as -40 C on a regular basis. I guess if you keep the water away it can get as cold as it wants. So I dig down until I pass the organic material which would be about a foot and do the "insulated footings", what about the 8ft of earth above the frost line below the footing that can freeze and thaw however it wants. I'll have to read more about this but if you guys are doing this in the permafrost it must work. I'll have to look into it a little closer. THX again.

MountainDon · January 18, 2008, 03:33:45 PM

IF dealing with permafrost go HERE. That's the University of Alaska at Fairbanks.

That page should open at the Housing Construction and Maintenance section. Have a look at the 4th article, # HCM-00754, entitled, Permafrost-A Building Problem in Alaska .
There's also a load of other articles.

Direct link to the permafrost article/download... Click for PDF Form

....from the article...

Wood piles anchored in the permafrost are considered the most stable foundation for arctic building. The piles should be well embedded in the permafrost and the structure raised above the ground to permit natural air circulation beneath the structure and to minimize heat flow from the structure to the frozen ground.

Piles are driven in place with a pile driver. However, the permafrost must be melted with a steam jet. The piles can be set in an augured hole filled with slurry and allowed to refreeze. Autumn and early winter are the best time to set piles for the next construction season. Piles should set undisturbed for a year until firmly frozen and anchored in place by the permafrost. Sometimes piles are fitted with refrigeration coils to hasten the freezing process. The tops of the piles are cut off 4 to feet above ground allowing free air circulation beneath the structure floor.

MountainDon · January 18, 2008, 03:58:22 PM

Further notes from Alaska (other articles)

1. Consult with an architect, engineer or contractor before building on soils subject to permafrost. This includes most of Interior Alaska and areas west and north of the Alaska range.

2. Enclosed crawl spaces or basements should not be constructed in soils subject to permafrost. Wood posts, mud sills or engineered foundations with open crawl spaces are suggested in permafrost soil.

lonelytree · January 18, 2008, 11:27:30 PM

I am right on the edge of discontinuous/sporatic. On the map it is near the lowest bottom right green spot.

Discontinous permafrost may or may not be under the lot. Without digging a hole I am faced with what others are doing that is working. I know that any method that involves digging a hole and inserting a post etc OR any piles driven WILL heave. Maybe not for a couple years but they will.

I have talked with many homeowners that have many different foundations. Since all will move, they suggest the easiest one with adjustability. Most are actually laying RR ties or green treated lumber on the base and criss crossing their way up. Personally I don't like the idea. I ran into a close neighbor and he suggested doing what he did. Cement pads with risers to the beams. I have looked at several types and have determined either cement (like in my earlier post) or 6" well pipe on pads.

My problem is compounded because the lake level is not over 8 foot down. I suspect that I would hit water at around 5-6 feet. Some areas of the lot have black spruce. Black spruce is caused by poor drainage and/or wet soil. The area is also experiencing warmer than normal temperatures.

It is possible that cement piers with insulation (ref: nash) may be even better.

No matter what. I will experience earthquakes, frost heaving, an occasional heavy snow and some winds.

January 19, 2008, 01:54:27 AM

Seems that if you are in perma frost it would allways stay frozen? Up lift happens when it defrosts and freezes again causing the lift. That is why you see so many rocks on the surface after winter, when you raked them all away during the summer. To me it would seem if you ancored the wooden posts real good inside a larger concrete square block down low in the perma frost and back filled it, let the back fill re/freeze again first it would not lift up because the concrete block frozen into the permafrost would stay down not being able to be lifted by the smaller wooden post above it. It would have to make a void below the concrete and push up the frozen ground backfill first above it using the post to pull it up. I can't see where this can happen unless the concrete fractures and the ancors pull out of it or the post tears in haft. If the perma frost melts during the summer there could be some lift but it would have to melt first. Am I wrong in this theroy? Mark

MountainDon · January 19, 2008, 11:03:02 AM

If there is actual permafrost someplace down deep then a pile/column of some sort firmly frozen in would be good. You must remember though that the section of the post/pile that is above the permafrost, where the ground might freeze at times of the year can also exert lifting forces if tje frozen soil /water mix can get a "hold" on the sides of the post/piles. That article made mention of doing something to prevent that. Something smooth.

I have a problem fence post here. It's in the ground 4 feet. Frost depth here is given as 18 inches. This one post has lifted enough over time to need the gate latch adjusted every few years. The gate is hinged to a post that's attached to the house and there's no evidence that the slab on grade house is sinking. It must be frost heave "adhesions" to the post sides during times of wet soil and freezing, methinks.

glenn kangiser · January 19, 2008, 12:18:33 PM

Quotefrost heave

...often found near a drunk in a snowbank.

kev_alaska · January 23, 2008, 07:53:16 PM

One of the things an oldtimer here told me when we were putting in our fence here in town was in order to minimize frost heaving:
a) Dig your footer hole past the frost line. 40" here in Los Anchorage, add 4" of gravel.
b) Wrap a plastic garbage bag around the bottom of your treated post. Tape the top of the bag so it stays put.
c) Drop the post into the hole and cement as needed.
d) 14 years with only one fence post (out of 23) frost heaving. My neighbor put his posts in sans bag and we are adjusting his gates and strikers after each freeze....

glenn kangiser · January 23, 2008, 08:00:59 PM

I wonder if it would be good to put drains in the bottom. On untreated poles plastic bags cause them to rot in about 4 years. I know treated would be better, but still they are not immune to rot. I assume the bag is to keep the ice from getting a grip.

If it works I suppose it is best to not fix it, eh?

Willy · January 23, 2008, 08:12:18 PM

Quote from: glenn kangiser on January 23, 2008, 08:00:59 PM
I wonder if it would be good to put drains in the bottom. On untreated poles plastic bags cause them to rot in about 4 years. I know treated would be better, but still they are not immune to rot. I assume the bag is to keep the ice from getting a grip.

If it works I suppose it is best to not fix it, eh?

How about slipping a PVC sch 40 tube around the post part way and let the frost heave slide it up and down instead? That way the grip of the freeze would attach to the PVC instead of the wood post. Just another idea to confuse things. If the PVC fit snug it would stabize the post in the hole from leaning. Mark

January 23, 2008, 08:30:47 PM

Quote from: glenn kangiser on January 23, 2008, 08:00:59 PM
I wonder if it would be good to put drains in the bottom. On untreated poles plastic bags cause them to rot in about 4 years.

It might take longer to rot considering the time spent frozen up there, vs. your CA post bottoms. Still, I think that's something that needs consideration. Glenn is familiar with the problems of repairing/replacing rotted post bottom ends.

skiwest · January 24, 2008, 12:49:34 PM

won't be perma frost. he's surrounded by muskeg. Muskeg is swampie land that has 10-20 ft of organic mater. can only drive on it if frozen. Its a work out to walk on , like walking on a two foot thick low density sponge.

He has a high spot so I would say level and sit wood on ground stacke to make a pier like every ATCO trailer up there. Gravel up there is hard to come by. if surrounded by wet no way can get heavy equipment in other than in winter.

sirmike68 · January 26, 2008, 01:05:11 AM

I think I have come up with a plan. I will contact the local railway company and buy enough surplus ties to make 14x24 "foundation a couple ties high and work up from there. I will clear off the organics and lay the ties on sideway blocks all around. If any major shifting occurs I will just shim where needed. Without any heavy equipment available I think this would be the most "do-able" for me.

sirmike68 · May 22, 2010, 06:34:09 PM

Well its been awhile and my project will start this June if it dries up enough to give me access. I have decided to go with treated beams 6x6 stacked to make a foundation of 6x12. My dimensions will be 16ft x 24ft and the beams will be comprised of 16ft and 24ft lengths. I then plan on making the floor side beams by nailing two 2x10's together for the whole outside edge of the floor and then using 2x10's spaced 16" apart for the joists. Will the 16ft span of the floor joists being supported on each end be sufficient or do I need to put another 6x12 treated beam down the middle for support?

MountainDon · May 22, 2010, 08:40:57 PM

To answer the joist question with accuracy there are a few details needed as well as the supplied 2x10 dimension and OC specaing.

Species
Lumber grade

Note that for floor joists the deflection limit is usually L/360, the average live load contents of building) at 40 psf and the dead load (joists and other building parts) at 10 psf.

The span for a joist is not necessarily the overall distance from one end of the joist to the other. If the joist is seated on a pair of beams that are a nominal 6 inches wide, or 5.5 inches true measurement, and if the outside faces of those beams are exactly 16 feet apart, then the actual joist span is measured at the inside face of the beams. In this example that would result in a span of 15 feet 1 inch.

There are two handy online joist calculators available. They use slightly different input data and produce either a maximum span for given data or a chart of options.
http://www.awc.org/calculators/span/calc/timbercalcstyle.asp
or
http://www.awc.org/calculators/span/reversecalc/reversecalc.asp

As for the beams please note that a pair of 6x6 stacked one on top of the other does not necessarily equal the same strength as a true 6x12. It can be close especially if they are prevented from sliding one each other as they try to flex with an applied load. Probably not a big factor in this case, but something to be aware of if you go stacking 2x material flat sides on top of each other sometime.