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caterpa

foundation height and grade

6 years ago
Just a couple weeks or so away from getting my build started......it is an ARG plan and I've reached to to him on this as well.

I own sloped lot. It is 2.24 Ac. The front 30 feet or so back from the road is essentially flat then it falls off fairly abruptly over a distance of approximately 10 feet to 15 feet. After the drop off it becomes relatively flat once again. Essentially I have a stepped lot.

My foundation guy came out the other day and measured with his laser. The distance of the lower step of the lot is approximately 13 to 16 feet below the grade of the road and by extension, the upper step of the lot.

My plan is to place the footings the foundation just below the current grade of the lower step of the lot. I need to do frost footings. But most of the rest of the foundation can be covered with enough full to protect from frost.

In order to have essentially a straight flat driveway from the road into my garage, I’m going to need to have concrete front foundation walls in the range of 13 feet tall. This is going to add considerable cost to the project.

I’m considering modifying things a bit however I’m not sure whether this is the way to go or not.

I’m considering having the walls of the foundation at the front of the house only about 10 feet tall. The obvious problem this creates is is it places the floor of my garage about 3 to 4 feet below where the road is and where my driveway would start. This causes concern about drainage issues. I certainly do not want water flowing down the driveway into my house particularly the garage. I’ve considered tackling this in one of two ways or both simultaneously. That is grading in the first half of the drive down and then up slightly to go into the garage. I think we can grade the lot well enough to do this. At the lowest portion of this down then up driveway I would place drainage grates within the concrete to divert water and then use tile to take this water around the garage and down the grade.

The guy doing my foundation is very reluctant to have the garage be below the grade of the road. I think the excavator has less concerns.

My question for you is, what do you think of this idea? Or would you try to tackle this any other way?

Thanks for any input.

Comments (18)

  • 6 years ago

    It might depend on the geology of where you are and how you can manage the water. Plus how much water/snow you get. In my neck of the woods, I'd have a wash out of the driveway at the low point in a very short period of time.

  • 6 years ago

    Upper Midwest. Snow rain etc.


    No bedrock issues.

  • 6 years ago

    I didn't get much from the description. Surely you have a drawing or at least a diagram of the foundation; why not post it?

  • PRO
    6 years ago
    last modified: 6 years ago

    In general, complex verbal descriptions are hard to follow but you did a pretty good job. What would happen if you raise the whole house 3' in order to bring the garage up? (The down-then-up grades do not appeal as a first choice. Also, the overall appearance of a house below road grade is not as good as one at or higher.)

  • 6 years ago
    OK here's a quick sketch.

    Hopefully this is visible.
  • 6 years ago
    The house has an attached garage with 3 stalls with a front entry.

    The lot also has a very slight slope left to right. 100 ft wide. Drop only of 3 ft, over the 100 ft, left to right.

    All of it with the profile I tried to post above. Garage on the left.
  • 6 years ago

    In my neck of the woods it would be very short sighted to save the money now and then have to spend a bunch of money later on grading and repairs etc. over the life that you live in the house. Figure out how much more it actually is and then figure out the cost per month for the time you plan live there and see if that extra few dollars a month will be easier to stomach.


    Consider what a very heavy rain will do if your house is lower than the road even with grading this could cause water to get into your house. Also the ground changes some over time so you will likely need to redo some grading as time passes to keep on top of it.

  • 6 years ago

    RES


    That is a great drawing. I wish I had that kind of talent:) I clearly dont based on the quality of my drawing.


    So, your idea you sketched is my current plan. Or original plan if you will. It is simply that that front concrete foundation wall is going to have to be probably 12-14 foot tall and that comes at a considerable cost over what I had planned. (10 ft). So I was thinking of adjusting the grade to the house rather than the house to the grade. My post was simply to see if anyone else had similar lot characteristics and how they dealt with it, or to get ideas from those in the know so to speak.


    Appreciate all the responses so far.

  • 6 years ago

    1) I don't understand why ARG did not provide you with the site plan.

    2) Blah blah blah midwest... blah blah bah. Snow rain etc.

    What is the footer depth @ the address you are building?

    3) It is simply that that front concrete foundation wall is going to have to be probably 12-14 foot tall and that comes at a considerable cost over what I had planned. (10 ft).

    Yes, and for this structural wall to be 13' + <"frost depth"> it is possible that the wall have to be thickend, pray at the frost depth that you will get a good clay and not a topsoil.

    4) So I was thinking of adjusting the grade to the house rather than the house to the grade. Ok, I hope You are not planning to grade the road toward your house.. or you house sit in the fishbowl.

  • PRO
    6 years ago

    How about cutting down the lot between the road and building site?

  • 6 years ago

    You could raise the grade of the lower level but you haven't told us enough about the site to recommend that and it might cost more than a tall foundation wall.

    Or you could cut at the upper level and fill at the lower level but you would still need to bring in granular material for the footings and compact it. You would need an engineer for that and the garage would still need to be a structural slab on fire protected framing.

    Did you not consider these costs when you acquired the site? What has changed?

  • 6 years ago

    1) I don't understand why ARG did not provide you with the site plan.


    I gave him the best information I had at the time. We thought the drop was 9-10 feet which is much more workable than what it turned out to be.


    2) What is the footer depth @ the address you are building?


    46"


    3) Yes, and for this structural wall to be 13' + <"frost depth"> it is possible that the wall have to be thickend, pray at the frost depth that you will get a good clay and not a topsoil


    It only needs to be 13' to get to grade since that portion of the wall will be 11 or more feet underground after fill.


    I'll step the footings down to match the grade.


    4) Ok, I hope You are not planning to grade the road toward your house.. or you house sit in the fishbowl.


    The road is concrete. Just thought of grading the lot down to the house then up again.



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  • 6 years ago

    PPF


    That is precisely my thought and question. Then sloping the last few feet around the house up and create a swale left to right to ease water down around the house to the right.

  • 6 years ago

    RES


    I did consider the costs yes. In had a significant cut in the price of the lot accordingly.


    But like every home owner/builder, I'm trying to be as cost effective as possible to get this built.


    To answer your other questions, I have considered a flat building pad at the bottom and raising the bottom level grade about 3-4 feet. Yes I realize I'll need a soils and compaction test if I go this direction. I have no idea yet the costs of that process. But may still be cheaper than the extra concrete and fill we are otherwise talking about.

  • PRO
    6 years ago
    last modified: 6 years ago

    Was brainstorming and wondering if something like this could be useful here. (Matt Risinger has some super informative videos about house building.)


    In another instance (that I cannot locate now) I saw a project where someone used massive concrete piles that they got as free leftovers from freeway building (which I see frequently as leftovers here, as they are always building on the freeway.)

  • 6 years ago
    last modified: 6 years ago

    Unless your soil has a low bearing capacity, drilled steel piles won't help and they would be more expensive.

    Maybe you could put the house up on above-ground concrete piers but until you hire an engineer, you'll be spinning your wheels.

  • 6 years ago

    If the lot starts sloping at 30’’, looks like the setback you get to use is 30’. Or buy a different lot. Or spend a ship ton on a very special foundation and dirtwork.