Timber frame vs. permafrost

[fuzzybear]

  Has any one ever built a "floating" Timber fame structure. I have been looking into this style for a long time, but I am worried about how it will hold up.  I live in an area where there is permafrost, and the ground can move as much as 12" a year. So this means no foundation. Everything must be built on blocking above the ground or on footers run down to bedrock.
  Doing footers is not an option for me because bedrock is at 50'. There is one timber frame warehouse that was built around 1899 in town but it was built with timber footers. They only had 20' to bedrock so they sunk posts and built on that.
  The main thing I worry about is the twisting. When I level buildings up here they can fall or rise as much as 3" from one corner to the next.  The log home I'm in now I have to level twice a year. Some times it's only off by 1/4", sometimes it's off by 3/4".
  When we build here it is on spf pads with 8x8 blocking.  I was thinking about building a timber base and tying the whole structure into it ontop of my pads. Any sugestions, comments would be greatly appreciated.
  Thanks,  Donovan

[shinnlinger]

I don't know much, but my thoughts are this "If your gonna build it, over build it"  "When in doubt build it stout" and that would apply here I think. 

If you went with decent sized timbers for your sills, posts,  eves, etc..and had beefy windbraces at the top and bottom and used sheet goods in your floors and walls I think you could build a box that wouldn't flex much, but you know best on how muck flex is good in your region.

[ARKANSAWYER]

  Are there any crushed stone footings in the area?  I ask because in Alaska they would build cabins on creek stone that was piled about 6 ft thick and 4 ft wider then the building.  Also they would pour floating concrete slabs and build on them.   Lots of places in the Artic they build so there is a way.

[fuzzybear]

Arkansawyer,
   I've seen lots built on floating concrete slabs in Alaska. But over here they just don't work so well. We have alot of permafrost and the Tintina fault line is rite here, we have alot of ground movement here.
   As far as gravel I would have to still dig below the frost line for that and that is around 20'. Also the area I am building in is VERY remote. I would have to cut a road in about 50 km. I would never get approval for anything like that. They had a fit when I cut a road on the ice to bring a d-6 down river to my island.
    Tomorrow I'll take a picture of three buildings we have here that are from the Gold Rush era, they are maintained for tourist. But they show what happens when you build directly on the ground, or try to put in a basement.  As soon as you allow any heat on the permafrost things take a drastic turn for the worst.  There is only a hand full of buildings here that do not need leveling at least once every 2 years.  Some of the buildings lean as much as 3" to one side.
   We have a bar here called The Westminster Hotel, Locals call it "the Pit", tourist come in and think they are drunk even before they've had a drink. It leans 4" south and 1 inch west. There is nothing they can do to fix it without bringing down the entire building. It was built in 1898 during the gold rush and was intended to last only 5 years untill the new one was built. 
   That's why we build on cribbing, so you can take a couple 40ton jacks and some shims and adjust everything when it goes out of wack.
   Because of the drastic movement here, was why I was curious about timber frame buildings. Would the joints withstand that much flexing.  Also I guess I should add that my material would be northern spruce with a VERY tight grain.  A 12" tree is around 300 years old. So it is very hard and strong.
  I want to thank everyone in advance for your input. ANY ideas or obversations are welcomed.
Donovan

[Thehardway]

This might sound wacko but has anyone ever tried building on top of a big slab of EPS?  I know in certain parts of Canada "shallow frost protected footers" are common.  They are usually built by using EPS barriers of varying thickness dependent on exposure.  EPS and SIPS are relatively light and could probably be flown in or transported easily enough.

Just thinking out loud here,  Use "Jumbo" SIP panels.  2 layers thick with seams staggered.  On top of this "floating platform" build the structure of your choice.  You would have to make sure the weight is distributed well on the platform (Not a clearspan structure) Or maybe better yet use a layer of SIPS and then heavily reinforced concrete poured over top of it to form a floating deck.  I guess the key to building there would be don't let it thaw, and distribute all weight evenly? 

Might even try an experiment using "Lite-Deck" or "Speedfloor" type systems poured on top of the ground.  Insulation should prevent interior heat from thawing out ground underneath. 

How about helical anchors?  They are steel rods with screw blades that can be turned into the ground to a specified depth without any excavation.  They then provide a support for structural elements. They are often used to level buidongs that are sinking or bilt on unstable soil.





By the way, if the ground moves that much how do they establish property lines :D

I assume things are pretty flat?  What do you do up there and how the heck do you have internet?

[shinnlinger]

Hardway,


Since my post I have been thinking a panel house would be the way to go.  INterior TF if you just had to have it for asthetics, but stessed skins all around for racking. I too have heard of insulated shallow foundations, but I have never seen one. 

[TW]

Now I am not very good at engineering English so please ask or comment if you do not understand my thoughts.

Trying to analyze the problem to the best of my limited wit.

You need either a structure that can cope with uneven settling, while not getting any serious damage, or a structure that is stiff enough to develop new load paths.

An example. Imagine a beam with three supports and two free spans of the same length, and a linear load on top. A simple form of statically undetermined structure.
Then the support in the middle settles. Suddenly we have a beam with two supports and a twice as long span. Then if the supports in the ends settle. Suddenly we have a beam with one support under the middle and overhang to both ends. These three situations create totally different stresses in the beam. There are two ways to overcome this: Either you put in a huge beam that is strong enough even for the worst of the three cases, or you scarf the beam somewhere so that no part of it has more than two supports. Then each part of it will be supported all the time in two points.

-You have plenty of snow load. This means that a stiff structure would become very very  massive. A timber frame house stiff enough to stand on three of it's posts with the others hanging in free air sounds impractical to build. That would require the entire walls to be built like huge parallel chord trusses, since you will never know which three posts will carry all the load. I think we have ruled out the stiff option now. It would be ridiculously clumsy.

-A scribed log building would surely cope reasonably well. The entire walls do in fact work like huge beams, even if the pegs do not have enough shear capacity to make these "beams" fully rigid in shear. Thanks to this lack of shear rigidity the walls will bend back and forth just like leaf springs, while getting no damage. Over here are plenty of old log buildings that have settled terribly without serious damage.

-A timber framed structure designed particularly to handle uneven settling. This would require a statically determined design throughout. This means that no beam nor plate nor ridge log nor truss should be allowed to have more than two supports. For instance plate and sill would have to be scarfed in every second span. The traditional corner braces would have to be omitted since they make the bents work like a undetermined frame with semi stiff corners. Only one diagonal brace could be allowed per wall. Traditional timber framing largely relied on undetermined solutions so this would be a completely new design. I am not competent to design it.

This is only my thoughts on the subject. Do not take my advice too seriously.

[sawguy21]

Why? You know what you are talking about. Fuzzybear lives in a mountainous area but as he points out, the ground is very unstable due the freeze/thaw cycle. Throw in the occasional minor earth tremor for an extra challenge.

[Thehardway]

TW,

You raise some good points.  In dealing wih permafrost I am assuming it is akin to building in a bottomless swamp or a sandy beach or even water. Buoyancy and displecement laws are actually more applicable than structural spans and tables. It is like building a boat. There is nothing to support a point load no matter where you put it.  Think of driving a wheeled loader vs. tracked loader.  The tracks distribute the weight of the machine evenly over a wider surface area.  It can be driven over mud and sand with no problem where a wheel will spin and sink.  The more widely and evenly you can distribute the weight the more likely it is to survive.  The heavier the structure becomes the more difficult it is to support (buoy).  

I agree with your assessment that a log structure would handle the shifting and settling well, just not sure about the weight of it as all the weight is on exterior walls.  Add to this the seismic activity and heaving action of seasonal changes it is really a ugly picture with just about any conventional building method. The best method of building would honestly be an inflatable dome on a styrofoam pad.

I once read about the military using inflatable balloons as dome forms that were then covered with foam spray.  The dome is an extremely strong shape and will deal with severe snow loads well.  The material to build such a building can be easily transported even into remote areas by pack animals and still make a rather large structure.  It is also a very airtight and well insulated form of shelter.  It just doesn't look real appealing unless you like to see yurts or igloos.

I have read where roads were built across permafrost using logs to form "corduroy" roads.  The logs in essence worked like floats and distributed the weight of the vehicles.  Perhaps a solid wood floor that is cross planked would work similarly for a log cabin? kind of like a double planked boat hull.

[TW]

I wrote a long reply but it disappeared somehow. I will write it all again as I get time.

We do not have permafrost here, but the ground may freeze down to two meters deep so frost hewing is a common problem. When the ground freezes the water in it expands. That creates a huge but uneven lifting force, that will easily lift any load. The lifting force become more uneven because when soil freezes the capillary action sucks the water towards the frost line. Therefore chunks of solid ice may develop in the soil. When the frozen soil thaws the ice in it melts too, and water has less volume than ice so in practice the soil contracts, but very unevenly. The water soaks the soil reducing it's load bearing ability greatly.
This frost cykle happens every year in the top layer of soil above permafrost.

Thehardway
There are many older roads and buildings built on timber floats on clay or swampland, in the Nordic countries. the problem is that the floats have to be constantly submerged in groundwater whatever happens. Otherwise they will rot very fast. The only problem I can see is a lot of digging by hand in a remote place.
A dome is only stable as long as it's supports do not shift. If a part of the perimeter settles the whole thing will become unstable.

There are forum members who were building before I was born.

[fuzzybear]

I know log homes are easier to level than stick built homes. We have alot of log homes from the gold rush that are still standing.  I was just thinking of something different for up here.
  We use timbers still for some bush roads. But like TW said they rot fast because of the thawing and freezing that happens.  In the summer they are hit with 24 hours of sunlight that helps dry them out and in the fall we have alot of rain just before freezing.
   Log homes must have long eves to keep the rain off of them or the logs will rot and split.
   When we dig through permafrost here it is with jackhammers and explosives. or the old way off lighting a bon fire and digging like mad when it burns out. The place I want to build in will be off grid so I have the logistic problem of transporting fuel to the sight if I want to dig. At $2000 an hour for helicopter drops It is to expensive.
   I thought of building a log base with all of my floor joist and posts tied into it. Kind of like building a large "Bird house" frame. This would then be leveled on top of cribbing.
   I was thinking of a barn type structure 24x32. The side walls would be 10' tall.
   Keep the Ideas coming PLEASE.  There are some good ideas that would work elswhere in the territory. I am Thinking of SIPS for another project where I don't have permafrost to deal with.

[Thehardway]

fuzzybear,

Had a idea last night while thinking about your problem and what TW said about a single weight bearing point.  When first exploring home building I was very taken up by the works of Fowler who was big on Octagon shaped homes made with wood forms that were then packed with gravel.  I being an efficiency nut I liked the Octagon shape as polygons offer more interior sqFt per linear foot of exterior wall than squares or rectangles.  Going on this I explored a number of prefab housing companies that built polygon homes.  Many of these were built for extreme climate areas since another advantage to polygons is smaller surface area for high winds to push on and better internal airflow for heating and cooling.

One of the companies I stumbled across was located close by here in North Carolina called Topsider Homes. I visited thier plant back in around 2002 and it was pretty cool. They built all of their homes in factory jigs for a platform that was mounted on a central steel mast.  The mast was drilled, driven, or anchored into the ground and then a platform was built around it and a patented steel tension ring system used to support the roof structure.  The floor was typically elevated about 7-8' above grade.  This area underneath could then be used as a garage, storage or laundry facility.  as well as house a stairway for entry. Many of these homes end up on beaches, mountain tops, or areas where excavating a flat stable surface was impossible or cost prohibitive.  In some cases they would drill directly into a rock face and mount it.  Here are a couple pictures off of their website to give you an idea what I am talking about




Size(diameter) was limited but multiple units could be built and connected together with passage ways that are free floating and allow movement between modules.

These modules were packaged into shipping containers and sent all over the world.

Perhaps a similar model would work for you in a timber frame design.  A large central post could be erected and the house hung from it.  It could even be gimballed if so desired for seismic issues and it would actually be able to rotate to follow the sun for maximum solar exposure.

Being that all the weight is on one bearing point there would never be any leveling needed.  With it elevated off the ground, ground should remain more stable.  Sips could still be used for roof, floor and exterior walls over a timber frame skeleton.

By the way I would have built that octagon house if it hadn't been for the fact that there was quite a bit of waste in plywood trying to make the roof/floor.  Getting the size right to maximize use of lumber was like a gigantic jigsaw puzzle. At that point I did not have my own sawmill and relator advised against odd shaped home due to difficulty in obtaining loans and poor resale.  I doubt these factors have much bearing on your project.

Don't know if something of this style would suit your fancy but between what you have said and TW's central bearing point I couldn't help but mention it as it more or less fit's the bill.

I dream of someday seeing that area of the world.  I imagine the land of the midnight sun to be one of the most beautiful places in the world.  If nothing else just for its pure remoteness.

Good luck and keep us posted.  I am very interested in how you will go about meeting your energy needs.  Is wind a viable energy source there in the winter?  No doubt PV's would supply all the power you need in the summer.  Will batteries actually function well in that extreme cold?

[fuzzybear]

Hardway,
   Thank you for the idea. I will have to do some research on that type of building.
As far as electric supply, Wind is an option, but I will probably be using solar and heat generated alternators to keep the batteries charged. I am curently using this system. You have to store the batteries in a warm area. You loose a great deal of amperage if the batteries are below freezing. I have a room that I keep at around 40f. In this room are my batteries and inverter, a 500 gal water tank, and cold storage of food.
   It's not hard living off grid, and even if I moved back to town I would still use solar as a primary source.  I've set people up with solar in town and they have reduced their power bills to $0 in the summer and to $20-$30  a month in the winter.

[TW]

Now I am running the risk of sounding conservative and stubborn and pessimistic and maybe even crude, but i will take it as it comes :

If you want something unusual and the material source is a spruce forest:

Why not build some version of log building not usually seen in America. Different parts of northern Europe has different styles so you can just pick the style that fits you. I posted a show and tell tread called "Finnish log building methods" once. https://forestryforum.com/board/index.php?topic=27608.0
The Norwegians have traditionally built very advanced and refined log buildings. I doubt there is any Norwegian style buildings in Yukon territory.

[beenthere]

TW
That was some interesting construction. 

Thehardway
Your suggestion of a central support post was intriguing, as then the possibility of having perimeter posts (like are shown in the background of the pic with the couple) that would be height-adjustable over time to keep the entire building 'level' as possible frost heave and/or settling would likely occur. 

When ya roll outta bed during the night, just know that it is time to change the height of the outer legs... ;D ;D :D :D

[Thehardway]

Beenthere,

That outer post is not on all of the buildings, only the larger diameter ones.  I noticed it after I had posted.  Some are completely free standing on the center post.   

Fuzzybear,  Interested in your off grid power solutions but I will PM you so as not to hijack this thread.

I love TW's log buildings.  Can't argue with +300 yrs. of history and still standing strong.

[fuzzybear]

TW,
  Actually there are alot of those style log homes here. I believe that most of them came from the Russians here.  The truth is that the Russians were here mining gold about 40 years before the famous gold rush of '89.  There is a cabin on my wood lot that was built with  blind dove tail joints. the walls are still standing although the roof has long since rotted away. About 30 yards away is a shaft  that is 45' deep and the cribbing was dovetailed in place. There is a boiler there that none of us can figure out how they got it there. It weighs around 10000lbs. If I can break the trail to it I'll take some pictures of everything and post it.
  Dawson City was the first city in north America that was totally electrified. There were over 50,000 people here trying to make their fortune. It was said that there was not a country on the planet that did not have people here. Some of the most colorful people were from Europe and Asia. They left their marks in the buildings and the land.
  When the weather breaks I'll head to town and try to get pictures of some of the European log home here.