rubble trench foundation with a basement

I live on 4 acres of land completely covered with quacking Aspen in the interior of Alaska. We have lived in our off grid cabin for 10 years. I am currently clearing the area for a 820 Sq foot house. I'll build using the cordwood method utilizing the trees I am clearing, and a rubble trench foundation. Our cabin is dry (no running water), and a well is much to expensive, $20,000, so I am considering a semi dry house. Storing large quantities of hauled water on site, but winter temperature is an issue. We have seen -63f. Keeping 500 gal of water from freezing is a consideration.  I am considering a basement, the soil is well drained, the gravel removed would fill the rubble ditch, heat from the house with limited augmenting should keep the water from freezing, and the basement would be a great place to store vegetables from the garden. My question is would a basement weaken the support for the backside of the rubble trench sufficiently that the foundation would fail? How far from the trench would be advisable to begin the walls of the basement? Any suggestions, or direction would be appreciated.

As a Civil Engineer my first thought was disaster!
But, I may be wrong.
Soil has a property called the  'angle of repose', which is the angle it will create if dumped in a pile from a conveyor in the air, for want of a better description.

If you draw a line at 45 degrees from the bottom of your trench towards the basement area and can have a basement
footprint outside those lines you will be ok.
45 degrees is a good working tool for this as an Angle of repose.
WATER IN BASEMENTS
I have worked with this topic for a while and collected information from many places.
I live in Australia where freezing water is unheard of. But as a water Engineer I try to learn about it.
This page will help a lot; rainfall catchment, storage and usage
In summary though,
- larger containers resist freezing
- keep the water moving
- have a small heater down there, keeping area just about freezing, but not that cold the house freezes.
- Aim for 4 months supply to reduce deliveries
- think about rainfall catchment, even if its limited
- insulate the tank with quality wrap.

In normal cold, I would say to get a couple underground cistern and bury them under the house.  For your cold, I would add a heating loop to the woodstove to warm the water and it would radiate back into the cabin.

If you can get a cistern strong enough to bury delivered to your location, I would second that as the best option for water storage under the house. If not, how tall will your storage tanks need to be (including any required top access)?

A true rubble trench would depend on earth on both sides all the way to the top. If you have rock that is not just round cobble, you should be able to build the interior face up to whatever height you need with a significant slope (like two or three feet of slope in six feet of height.) This would be durable with even minimal stonelaying skill and rock quality. Gravel would not do it, though. With that, you need to depend on the angle of repose. An 825 square foot house would presumably be about 25' in minimum dimension, so 6' in from each side leaves a good 10' of flat floor with 6' headroom, plenty of space for tanks.

Thanks for your response! I will have to do more research on maintaining back pressure against the rubble trench. As the house exterior walls would be 24" thick, the trench would be 48" wide at the bottom and 36" at the top. The inside wall deminsions are approximately 28'x30'. I was thinking that if I limited the basement to half of the exterior footprint or about 400 Sq ft, that would give enough room for the water storage yet maintain sufficient  structural support for the foundation.

Prevention of the water freezing is indeed a problem. The Tanana river isn't far from here, it has depths close to 20 ft in places and is several hundred yards wide, yet in January it will freeze solid enough to drive a D7 bulldozer across, as fresh potible water is 85 miles away in the winter storing 500 gals (3-4 months) of water would be very nice! Other than a basement the only thing that comes to mind would be a underground tank, which is difficult to maintain, or a separate heated building which is expensive to build and heat through the  winter.  

Remember that this homestead is of grid, and December sunlight is limited to about 4 hours a day, electrical heating is not an option.

That is exactly the type of basement I was considering. Using roughly half the size of the available space inside the foundation footprint. Frost line up here is 4 1/2 ft, I was thinking of a foundation depth of 5ft, a basement depth of 6 1/2 ft, that would give a headspace of 7-7 1/2 feet. More than enough for wiring and plumbing. Yet dug 10 feet from the interior wall of the foundation trench.

Somewhere on this forum is the storey of a bloke who had a tank inside a barn, each year he made improvements and
finished with a small wood stove that heated the tank room enough to stop the tank freezing.

I have seen Canadian wood heaters that burn 24 hours on a load!
Or a pellet heater.

So with a base of 4ft x4ft and a height of 6ft, we can hold 500gallons of water.
You can also stack two IBC totes and you would be able to hold 500gallons of water.
If all you want to do is hold 500gallon of water I recommend making an extra small room in your house and storing it inside the actual house.
You can put the water tank/IBC totes in the laundry room or in one of the 3 bedrooms below

On a different note, what do you think of the cabin design below, and do you mind sharing the design of your cabin.



In one of those 10ft x 10ft your could fit Four 250gallon IBC totes and still have a walkway. You can also stack them 2 layers high, so you can actually have 8 of them in a room. Thats 8*250gallon = 2,000gallon. If you made the bedroom 12ft by 10ft, you could fit 12 IBC totes vs just 8 so that would be 3,000 gallons vs just 2,000gallons.

A 250gallon IBC tote is 42inch by 42inch by 42inch

S. Bengi,  the cabin in your reply wouldn't be useful for us. The 2 extra bedrooms wouldn't be useful, and as we have a dry cabin the bathroom would be a complete waste. If we had children living with us it might be worth figuring a way to heat all the bedrooms, but I think I'd rather just add a loft. It's easier to heat as hot air rises, it reduces the cost of the foundation and the roof area, which are a large portion of the expense in building and it makes maintenance easier.

Our current cabin is a simple frame built 16x20 with a 5 ft front porch,  it's completely open in the interior, the kitchen area takes 8 feet on 2 walls, the bed is along a third wall and the living area takes up the remainder of the floorspace. The foundation is packed gravel in a hole dug to below the frost line.

There are many things I'll do differently for the house. I'll use a rubble trench foundation for the perimeter of the house and post in footings to support the floor inside the perimeter.  The exterior walls will be cordwood 24" wide made from aspen logs. With the addition of water storage in the house I'll have a bathroom. There will be two interior walls separating the bedroom from the kitchen/living area, and a wall separating the bath from the bedroom. Primary heat will still be wood, using propane at night. I'll add a entry on the front and a vestibule on the back door. The interior walls will be 2x4  frame. The attic will be floored but unfinished for storage of non temperature sensitive items, the basement will be heated for more sensitive items to be stored. I think I can get roughly 340 to 400 feet of basement maintaining a distance of 10 feet from the foundation trench. That should be sufficient keep the foundation intact even with the weight of the walls on it.

You could do concrete block walls or pressure treated wood or PSP for the smaller basement fairly cheap and easy.  Water storage and root cellar.

You haven't said how you plan to transition from rubble trench to basement. Are you just going to let the ground assume its natural slope, or are you going to have something to hold the ground back from the basement area? Do you have access to any stone beside gravel? If you plan a sloped grade transition, the sloped area can still be very useful for storage.

What is the frost depth in ground there? Is your rubble trench going to extend below that? How will you keep the walls from heaving, or will you?

John Daley did a good job of addressing the construct of the basement.   As for the water, I lived in northern MN and regularly saw weather well below -40.   My record cold was -53 f.   The big question for me is if you are planning on leaving the house for several days over the winter.  If you are not planning on being gone more than 24 hours, I don’t see a problem.  I never had my water freeze, and I certainly didn’t have the benefit of massive tanks of water.

We knew people with a well built log cabin on a thick concrete slab.  They would be gone 5 days without the temp dropping below freezing.