Building Pad Construction

[AmericanLandMgt]

Hey guys. I am building my house on some property that I have owned for a while. The land is really wet and you cant dig deep enough to dig footers without hitting water so I want to build the area up a couple feet and then dig the footers into the new fill. The soil is mostly yellow clay that compacts really well. How do I go about compacting the fill material so that it is suitable for digging a foundation into? I have a TD-20 I was going to use to compact it. Do I just need to do like three inch lifts and then track back and forth on it or do I need to get a compacter out there? This house is going to be in the family for a while so I dont want any complications in the future.

 

[heavylift]

clay isn't a could material for under a building... it swells ... then shrinks... in cycles... floors crack
most building around here use a material that they call Low Volume... which means a low volume of clay.... It's a sandy top soil dirt... and it compacts very well...
we have dug out 100's of loads of clay at a site, then haul in the low volume...

as for building on top over shallow water table water.. they do it around here, but the home don't have basements , and are for the most part slab on grade..

Might want to have the area tested first by the dirt tester people...

 

[DGODGR]

x2 on the clay being expansive. Caisons might be a better fit for your site.

 

[D6c10K]

That's interesting...around here, when building roads commercial buildings etc, they seem to always strip all the topsoil and fill with clay and compact. They may not be using just any kind of clay so there may be the difference. Where it's wet and have trouble getting it to dry out or compact to spec they mix in fly ash, but that's more on road type work.

 

[tootalltimmy]

Here we use 6" minus gravel and top with 3/4" minus gravel. I would think about dealing with drainage first?

Putting this on top of clay on top of water sounds like future problems.

12" lifts will give you good compaction.

You could rent one of these in Canada for $155/day. Would do the job.

 

[stumpjumper83]

I used to live in south east pa, where developments were the rage and I was employed by a contractor that kept 150 guys busy building developments, when the pavement was in, we were out. Major site work only.

Any fill that was going to be a road or house pad was regularly tested as it was put in for moisture content and compaction and it had to pass both. Compaction was achieved with cat 824 soil compactors and dirt rollers like ingersol's sd120, 12" lifts... etc

Between you and me, I will never own a house on fill, unless its on piers that go down to virgin earth, bedrock perferably.

If you must have a house in that exact location, over excavate it with that td20, push that yellow clay away somewhere and replace it with some something with structure.

 

[ttazzman]

call a soils engineer..........or build on piers to virgin soil/rock.........this is not a place to be guessing and taking internet advice

 

[Tinkerer]

How severe is the water situation. Is it like a swamp with surface water on occasion ? We have both yellow and blue clay with a moderate amount of water infiltrating it in our area. Basements are dug and erected on a regular basis.

 

[joe03dodge]

get the site and the pad engineered,you will not regret it. most of the time a dozer will not get to corect compaction.

 

[AmericanLandMgt]

Wow didnt realize it was that big of a deal putting in a building pad.

I will call the soil guys and get their opinion before I start pushing any dirt around.

The house is going to be built on a crawlspace foundation with footers. Basements are pretty much unheard of around here. The land isnt swamp, I may have made its sound worse than it really is, its just that when you dig down two feet or so you start to hit ground water. There is no surface water on the properly graded areas. That being said, some water does pool up in the enormouse skidder tracks that the loggers left behind.

There are houses built all up and down the street ranging from slab houses to gigantic houses on crawl spaces, but none are built on pilings, Ive owned the land a while and watched most of the houses go up. As far as putting something down to bedrock, when I had my well put in they didnt hit rock for two hundred feet so I dont think that would be doable.

I have a plate compactor that I use to install walkway and driveway pavers that I can use to compact the soil if the dozer wont do the job but its seems like renting a roller would be the way to go. The clay is actually called clay sand, its not that nasty thick georgia type clay. It seems like standard procedure here is to clear and grade the land, then dig a drainage pond and use the spoils from the pond to build up anywhere that needs fill.

As far as over excavating Ive got a track hoe that I can dig out as much as I need to, but the soil is the same composition after you get out of the top soil layer. My pond is 20 feet deep and its all the same dirt after the first foot or so.

How long do you have to let fill dirt sit untill its considered virgin soil again? I know of an old sand mine that they filled in with inert fill (concrete chuncks etc) and then build houses on. This has been years and years and they dont seem to be having any problems.

Sorry for the long winded reply and thanks for the good info!

 

[ttazzman]

since you dont have experience with soils in your area you need a soil engineer.......reason being you need to find out how much weight your soils will bear so you can put in adequate footings.....as mentioned by others soils can be extremely different and clays can go from being great to build on to swelling up when wet to turning to mush when wet.....so even if the common practice in your area is to "borrow" soils from a drainage pond to build on you need to know how much fill to place so you have the recommended amount under your footings......I consider "virgin" soil to be 100% compacted soil some soils you can compact to 100% yourself if you get the moisture content just right and some soils 20 years from now will still not be "virgin" again.....the problem with any soil less than 100% compaction is it WILL settle ...how much settleing and how fast is the problem....in any case wet soils are a problem and need special attention to get things right....and the worst thing you can do is Half-arse your foundation and deal with problems forever with the building..

lotta ranting hope it makes sense

 

[Dickjr.]

I don't see need in a lot of this . There are two ways to approach this , dig a 4 foot wide footing 4 feet deep , line it with geo cloth fill with # 57 stone , compact in lifts , pour footer and low wall. This will allow the soil to move and provide a sure foot for the building. The rock will allow the movement do to drying and wet conditions. The 20 will compact the soil well when done in lifts as long as the clay is allowed to air to a point that the moisture is not to high. I usually notice when it crusts over its time to walk it in. The first idea is an engineering approach to the situation , for large buildings , the later will work for homes , just put a pad of rock under the footer for movement and backfill 5 feet around the house with loose topsoil and it should be fine.

 

[Greg]

Having a soils engineer is pretty cheap insurance. If it settles or shifts after you do it his way you have him to go after.

 

[joispoi]

How long do you have to let fill dirt sit untill its considered virgin soil again?

I´ve got an answer that would earn me some vacation time from here. Think in terms of people. How long do you have to let them sit?:cool2

A compaction test is the only way to know if the soil is stable.

 

[AmericanLandMgt]

Think in terms of people. How long do you have to let them sit?:cool2

HAHA never thought of it that way.

What Dickjr is saying is more like what I see done around here all the time.

I talked to a soil guy and he said he would engineer it if I would like but usually people just drain the area around the footing with a deep ditch and retention pond, put in the footings then grade everything to the pond and fill in the ditch with stone. He said that way you broke the hard pan soil that holds the water and the topsoil is graded to the pond so the problem dosnt arise again. As far as the fill goes he said to lift it a foot or two but scrape the area first and dig down to the first little bit of virgin soil. that way tou have your frost protection with the thickness of the pad, and the house is sitting on virgin dirt. He also said to add some stone to the bottom of the footings for any water problem that might arise in the future.

I think I am going to do all of the draining and dig a little test footer somewhere close to the house and see how the water does. If I am still unhappy with it Ill call him and get him to do me a site plan so I can pin it to him if things go wrong down the road.

thanks for all the great advice.

 

[waller92]

Hey guys. I am building my house on some property that I have owned for a while. The land is really wet and you cant dig deep enough to dig footers without hitting water so I want to build the area up a couple feet and then dig the footers into the new fill. The soil is mostly yellow clay that compacts really well. How do I go about compacting the fill material so that it is suitable for digging a foundation into? I have a TD-20 I was going to use to compact it. Do I just need to do like three inch lifts and then track back and forth on it or do I need to get a compacter out there? This house is going to be in the family for a while so I dont want any complications in the future.

Hi there in Ireland we use lime to stiffen the ground as u apply each lift apply the lime and compact it in this stops the swells and shrinks and then use a raft foundation to stop the cracks

 

[Forestgnome]

Besides all that's been mentioned, a dozer is a terrible choice for compaction. They have very low ground pressure. A regular pickup will compact the soil more than a dozer.