To pile or not to pile? That is the question. 🤔

Hey everyone.

This is the picture of the land that i'm buying (i'm buying 2 lots only). I was told this land is flood-free. The soil is black/dark brown and you can see the forest in the surrounding area. I was also told that to build my house here, i would first need to pile up the ground (with red clay soil at least 2-3 feet high).

Thing is, i've watched tons of Youtube videos and some of them dig up trenches 2-3 feet deep and fill them up with gravel, before adding layers of soil and finish them up with boulders/big rocks on the surface. While some others build their house foundation straightaway on the surface.

So my question is, if i were to pile up the ground before i can build my house, and i'm suppose to dig trenches as well, won't it be redundant? I mean, first, i ask them (the people i'll be hiring) to pile the ground with hard clay. Then after they're done, i ask them to dig the trenches around it? They might think, why would i ask them to pile up the ground if after completion, i ask them to dig it back? That's like doing the same job twice.

Hence, i'm kinda confused here. Do i pile up the ground, or do i not? Do i need to dig trenches, or straightaway build my foundation on the ground?

Please advice!

Did you ask the one who said the region does not flood why you have to build up the site some three feet?

Alden Banniettis wrote:Did you ask the one who said the region does not flood why you have to build up the site some three feet?

Because you can't build houses on that land without piling up the ground first. As you can see from the picture, the soil is black. It's more suitable for agricultural purposes like gardening/planting. Hence, to build a house, one must pile the ground first with red soil, at least 2 feet minimum (standard is 3 feet).

Thing is, i've never done a cob house before so i don't know if i should/suppose to dig the trench or can i straightaway build the foundation on the surface?

There are 17 other lots next to my land. If i don't pile the ground by at least 2 feet minimum, my house would be lower than my neighbours'. In case it rains heavily, extra water from my next neighbour would run to my place since my land is lower than theirs.

Well, I have never heard that agricultural ground needs such a building up, but then I am no engineer.  I am surprised that one could not skim off the organic upper layer of soil and then either fill it with gravel, earth-packed tires, or just put in piers.  As for the trenches that you mention, well, I like that idea in general for drainage and I think that all homes should have drainage put in- and plenty of it.  I think that, cost-wise, piers should satisfy the conditions you have.  But those piers have to go down past the frostline and then as high as you need to be above ground.  I would do the piers inside the perimeter of the trenches.  And then you could make some use of the crawl space maybe.  I am sure others on this forum are going to know exactly what your options are.  I am building a cordwood house up here in northern Maine.  Clay soil.  I am doing an insulated rubble trench foundation and I will be raising the structure a couple feet high to be above our crazy snowfall.  I am using earth-filled tires for that.

I think people are confusing apples for watermelons.

Has this advice come from the local authorities or others?
What is the aim of the works?
Is the land actually flood free or is that a rumour?
Agricultural land will need filling if its flood prone.

Trenches are often dug to create strip footings.
Foirmwork can be installed about the ground for the same reason.

Do you know how deep the black/brown soil goes? If it is really rich in organics, it will compress when loaded. I can definitely see trenching to stronger soil, and removing some topsoil from the floor area and replacing with gravel. Clay once it settles or is compacted will give a strong base, but no drainage at all. How flat is your lot? Can you run a drain from the base of your trench to an aboveground low spot? You would be safer if you can do that, and if bringing in fill is needed, it would be worthwhile. I would see no point in dumping clay and then digging down in that; if adding fill, I would make a pile of it in the middle of your footprint, then trench around the perimeter, put in whatever foundation you plan, and level the pile to give a good base for the floor slab. I am assuming you will have a slab because an aboveground wood floor would have zero need for a pile of fill under it.

What is your climate? How much frost do you get in the ground?