hello and a few questions

[leinom]

Hi, I'm new the board here, and I have recently started on a 16x 16 cabin but I am having some water troubles. I'm in thick clay soil that goes down three feet into a sand bottom, i have holes dug, and 5 of them have over a foot of water, and i keep bailing them but they just keep filling up. I have been told by a local contracter that I should just fill the holes in with crushed rock and set concrete pads on top. I'm going to be using treated 4x4s for my posts, and i already bought some concrete... I have worked for a plumber for 4 years but I don't know too much about  building so any help you guys could offer would be great. Great forum guys...


Mark

[youngins]

Hello and welcome...

I had exactly the same problem with the holes for my playhouse. I would bail them out on the next sunny day - with no additional rain they would just fill right back up.



It appears they were filling with underground drainage water.

I was stressing out about them as well - and then DW (dear wife) gently suggested I just fill them in with good drainage gravel.  I asked around and a landscape company suggested limestone gravel.  

Got the holes bailed out, filled in with some limestone gravel - enough to "quasi" level the piers, set the piers, pour gravel around the piers..



It took about 800lbs of gravel. Ignore the built-up beam / piers - they got butchered (not one of my better ideas ).

The piers have been rock solid through many flooding events.

So far, it appears DW was right about this one....

[leinom]

Thanks very much youngins for the great pictures. I was just worrying about the concrete getting wet too early and never drying properly. I'm also in central MN and code states 4 foot footings, but its a hunting shack right? I'm still kind of inbetween on what method to take I like the thought of having my posts roughly 3-4 feet into the ground, but if it heaves up and I have to take them out next year that would not be good. I would like to talk to some more people and see if piers sitting on crushed rock on the surface would work. I'll keep thinking and asking questions and won't jump on anything right away. Thanks again.

Mark

EDIT: What is your frost depth? or what part of the country are you in

[youngins]

How about pre-cast piers from home depot - or wait for a dry spell??? Also, trying to find a way to keep water from draining into the piers might help (like what I attempted to do with the lawn edging).

I am in North Texas frost depth is basically nil. But I do have to deal with that clay soil.

I am sure somebody from the "brain trust" will jump in with some sound advice rather than hearing about the adventures of a computer geek trying to do construction.  

[John Raabe]

The best advice is not to build in a high water table area. An area that won't drain properly can have lots of problems with frost heave, bugs, mud and mold.  Foundations need to keep their feet dry to have a long life. Only then can bearing and stability be assured.

Perhaps a french drain can improve the soil at the building site.

If you are stuck with wet soil but can be assured of solid bearing at the bottom of the post hole then you might be better off with foundation grade PT posts rather than trying to do concrete. You can backfill the hole with gravel. Wooden posts rot only about 6" to 12" above and below the soil line - an area where both moisture and oxygen are available. Wrapping the post with a waterproof membrane at this vulnerable transition could extend the life of the posts.

[leinom]

Well I have a pretty good idea of what I'm going to do. I'm going to make 12" round piers and set them on top of ground, over all the holes I have filled with crushed rock or gravel. Over the tops of the piers I'm going to build up a mound of gravel then cover with tarp and mound wood chips about a foot up for some insulation type deal. Then I'm going to build up from the piers with about two feet above ground for the bottom of the floor, using two beams similar to what youngins did. Can anyone add anything to my idea or comment on whether it sounds ok or too much or not enough? I have never built a foundation before and its kinda new to me. Thanks!

Mark

[glenn kangiser]

Lakes nearby?  Much of the water producing sand is like quicksand and will move out from under you -- or your pile of rock.  Have you tried to drive a stake down into it and see if you hit anything solid?  You are talking about sitting several thousand lbs. on each of these piers so it would be interesting to see if it has a base - bedrock - rock etc - under it.

[fishing_guy]

I'm also in central MN and code states 4 foot footings

Lakes in Minnesota?  Only about 10,000 of 'em.  Even though it is "only" a hunting shack, make sure you get it right.  I have seen to many of the shacks look like heck after a few years.

We bought some land north of Hibbing last year, and I fear we'll have some of the same issues you're facing.  Dug a hole to bury fish guts last week, and the hole was half filled up by the time I got done cleaning them.  Of course, the 1 1/2 " of rain we got the day before didn't help any.

I know that things can be built in the area, because there are 2 houses already built.  It's just a matter of getting the correct drainage.

[leinom]

Yes there is a lake about 300 feet away, but I'm also about 200 feet higher than it on a ridge. A little background from what I have heard about the soil out there- a friends dad who used to build septic systems said that there was about three feet of clay and then a layer of sand that held water above another layer of clay. I would assume that these holes I dug would never dry up. There is homes around the area, many that are much lower and closer to lakes than mine I'm building. This is going to be interesting to see how it turns out. I guess I'll just have to keep asking questions to see what the best way to go here would be. Its a beautiful spot on a ridge over looking a PRIVATE lake! Not a single house and county land bordering half the lake and not enough land between the road and lake to satisfy the countys 100 foot set back. But if worse comes to worse, guess I'll have to move my build site to the other 80... I'll see if I can remember to bring out my camera tonight and take some pictures of the area. thanks again,

Mark

[leinom]

I'm also in central MN and code states 4 foot footings

I know that things can be built in the area, because there are 2 houses already built.  It's just a matter of getting the correct drainage.

What kind of drainage are we talking here?
thanks

[glenn kangiser]

If you are on a hill it could be as simple as trenching down to the sand layer - throwing in a few perforated drain lines - maybe with a screen sock and or gravel over it - taking the ends out to a lower level down the hill a bit so it will just continuously de-water the area where you want to build - called drain to daylight.



From here   http://www.askthebuilder.com/B70_French_Drain_Design.shtml

[leinom]

Well it looks like I'm going to be moving my build site to our other 80. I went out last night looking for drier land, and used a soil tester to dig down. 4 and a half feet of sandy-clay in the spot I'm thinking, right on the top of a ridge. Insulated three foot footings is what I'm thinking about doing now, and I even have a friend with an auger for the Bobcat! Should go well, I'll take pictures! Thanks for the info guys

Mark