Hello,

I am new to this group so bear with me.  I am building a small cabin up in the woods of Upstate New York in the next few months and had some questions, primarily about foundation ideas and drainage issues.  The property is small, only about 5 acres and is seasonally wet.  Since it is dense hemlock forest with little sunlight and most clay for soil, this time of the year it is usually rather wet.  Can I install a gravel pad that is about 16' wide by 32' long and then place 2'X2'x2" concrete stepping stones (for lack of a better term) and then top them with concrete chimney block.  I would space them about 6' apart and place them every 4' along the length of the cabin, the cabin will be 12' wide by 28' long.  My biggest fear is the gravel pad shifting and causing the cabin to shift out of level.  I figured on making the pad about 12" to 18" deep.  It is nearly impossible to get a concrete truck to the property and I tried digging holes for concrete tubes, but finally gave up when I hit clay and massive amounts of solid rock.  Another issue I am facing is the problem of standing water.  Do basic french drains with perforated plastic pipe really work as well as I have been told?  Any help would be greatly appreciated.

Jeremiah

Hi Jeremiah,

Don't make a bathtub --- hole in clay filled with sand or gravel = bathtub --fills with water.

Can you dig down with a power auger to the bedrock for stable piers - anchor to it and pour piers?

French drains work well if they have a place for the water to drain away to.

Glenn,

Thanks for the fast reply.  I think I was not so clear about the way the gravel pad would be built.  The pad will be above the grade surface.  I would only scrape the surface of the ground to try to get the pad site as level as possible, but 95% of the gravel pad will sit above grade.  There is a small spring fed stream in the back part of the property, which is probably were I will have the french drain, drain the water runoff to.  Thanks for the help.

Jeremiah

  Glenn!  "don't make a bathtub" ! Wow, you just said a 1,000 words with the picture in my mind.  That picture, and understanding, will stay with me forever.  Thanks!

If you are in wet soil and are expecting to bear the weight of a building on that via a gravel pad you are not likely to have much success. This kind of ground is not suitable for much of a structural load. In clay soils in NY state you can also expect lots of frost action.

You can do what indigenous folks have done for thousands of years - pound poles into the muck until you get something approaching solid footing. Even then they did buildings lashed together so they could make adjustments as things settled and moved. This same technique has been updated with steel pilings that are done for all kinds of buildings in poor soil. This is very expensive of course. You basically keep pounding an I-beam into the ground until you meet the required design resistance. With enough money you can build just about anywhere.

If you have a slope and can get a French drain to carry water away you may have some luck in drying out a selected area. Then you could analyze the soil to see how much silt and clay are there and what it might do when it freezes.

You might explore what is built in Alaska where they build on permafrost that melts in the summer. I think they use floating foundations on gravel pads. It is possible to design a small building like an Ark and float it on beams connected to piers resting on crushed rock pads. The building will have to be re-leveled periodically as the ground below moves up and down. You may have to lift and refill gravel trenches if the soil "eats" your foundation! Bottom line: you wouldn't want to do this with an expensive building.

Not all land is economically buildable - there are lots of properties that should not have buildings built on them. Look at New Orleans!  

Well Glenn (DAD) it sure would be nice if you could come up here and help me construct a shelter of cardboard and duct tape.......One that won't get sop and wet with rain, blow away in the wind or fall apart, that's all that I can afford with these high gas prices... We were told by a broker we could get a home loan for $77,000 but that's pretty much a 780 sq foot house with crumbling foundation and leaky roof, in these parts.   :'(

Gravel sinks into wet clay surprisingly quickly. I spent one summer walking to work along a road built on wet clayey soil. Every 2 to 3 weeks the town would lay down a fresh 8" layer of crushed rock, and a couple of weeks later it would all be muck again. That was during the dry season and this road did not have a lot of traffic.

If I HAD to build on such a site, the first thing I would do is
identify what area is the highest and best drained naturally.

Then I would bring in a large back-hoe, or crawler, and strip off all the top layer of soil that contains any trace of vegetation..... and temporarily locate this material away from the house site.  On an area about 6 times the footprint of the house, I would try to pull clay and rock into a mound in the centre to support the building ... at the same time create an peripherial area drain several feet away from the intended building.

Then I would watch it for about a year to see if the drain worked and if the mound was "high and dry" ... perhaps a few test fence posts installed ay different depths on the foundation mound would give an idea of what winter frost will do.

If it looked okay, I would plan a small structure, using piles that went down to undisturbed earth or stone, that could later be expanded.

If you've got the time, JRR.  Sounds like a good idea, and why people often recommend living on or near your land for a year.

The guy (real estate agent) who puts out the booklet on the Alaska Log Cabin--vertical logs--seems to indicate that a floating foundation can be made with just a slab with the edges thickened, IIRC.  Don't know if he's right.

I was noticing today how much a couple of pallet-shaped stacks of concrete blocks have settled and shifted in the last couple of years.  They were put on fill dirt, nowhere near the septic tank or drain field, quite a bit of erosion coming down, but some of the blocks seem to be a couple of inches lower than the rest.

Soil consolidation at work.

Looks like Angie needs another roll of duct tape. Another reason for this forum - at todays costs many people can't afford to have houses built --- have to learn the do it yourself tricks.  Hopefully it makes it possible for more to be able to build their own home.

Frank - the bathtub explanation was given to me years ago by a good engineer explaining to me about a similar situation.  Badly expanding clay -  --- we mounded - graded away and dug a 3' deep reinforced perimeter footing to keep the clay underneath dry.  We ended up with a very stable foundation on a 50 x 120 or so building --30 yeas ago almost -- for a customer --- no problems ever mentioned.

Daddymem says

QuoteSoil consolidation at work.

He's right too.

Perhaps you could/should look around your area and talk to others who have built on similar soil.  What has worked for them, and what hasn't?  Local knowledge and wisdom might be of value to you in helping to decide how to proceed.

Best wishes.

Thanks to everyone for their invaluable information.  I think I am going to ask the other two cabin owners on both sides of me how they went about their foundations.  I know the one cabin is up on a gravel pad and other is up on pt stilts.  The cabin with the stilts has sunk a bit on one side, but the cabin that was built directly on the gravel pad seems fine.  Of course I have not been to both properties for a long period of time to see the amount of wetness in both areas.

Best Regards,

Jeremiah