Q&A / 

Tips on Foundation Soil Grade Around Houses

New Construction

New homes and room additions are frequently the victims of poor planning with regard to grading. I can't tell you how many houses I have seen that were put too deeply into the ground. This condition causes marshy ground, wet basements or flooded slabs. In virtually every case, a simple drawing or calculation would have solved the problem.

Many modern building codes have responded to this problem. They require that the top of foundations or slabs be at least 6 inches above the highest point of soil at any location around the house. Furthermore, the ground must fall away from the foundation at least 6 inches within the first 10 feet around the perimeter of the house. Note that this is a minimum requirement. The more slope the better.

Using these calculations, this means that when laying out a new house, you need to pay attention to the existing grade before you dig. In fact, you need to site the house and see just what the highest elevation of the ground is at any point within 10 feet of where the foundation will be. Knowing this, you can now begin to dig the foundation.

I always made a point to put the top of my foundations 18 inches above this highest point. You would be surprised how quickly the dirt from the hole disappears when spread out around the house. Although the foundation would look high prior to backfilling, the ground had a very gentle slope once all grading was completed.

In my opinion, you can never have too much slope away from your house. My guess is that anyone who has a wet basement or ground that slopes back towards their foundation will agree.

Existing Construction

Those of us with existing houses that have grade problems face different challenges. Landscaping, sidewalks and other improvements must be dealt with in trying to correct grade problems.

If you are lucky enough to have a sloped lot, your task of establishing grade can be accomplished. It may take a small piece of earth moving equipment like a Bobcat or skid-steer loader, but it will be worth it.

If you have a situation where ground is slopping towards your house (houses built on hillsides), the trick is to slope the ground gently by creating a swale. This swale, or ditch, allows you to do two things. It gets water away from the house and at the same time collects the water which runs downhill towards your house. You direct this swale around a corner of the house and continue until the natural slope of the ground is falling away from your structure.

Flat Lots

Those of you who live in houses on flat ground face a more serious challenge. Sometimes the ground is so flat that there is no way to easily create a swale or sloping condition. In these cases, you need to pipe roof water as far away as possible. Downspouts that dump water onto the ground near the house can cause serious problems. You would be surprised at the volume of water a 1 inch rainfall can produce.

You can also consider surrounding your house with a moat, something like the old castles used to have. This moat is simply a ditch that is dug around the problem areas of your house.

You dig this ditch as wide and as deep as you can handle. A 2 foot wide by 2 foot deep trench can be very effective. Once this trench is excavated, fill it to within 1 inch of the top with large 1 inch washed gravel. This trench acts as a collection area for surface water. As long as your soil can absorb water (even at a slow rate), you will have improved drainage conditions around your house.

Only in very wet seasons, when the water table rises around your house, will you experience problems.

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21 Responses to Tips on Foundation Soil Grade Around Houses

  1. What if the amount of water coming onto my property is so huge that it has( and will) continue to wash away my topsoil. I live in city limits and I feel that waste water is directed onto my property. I am told that since I live on lower grounds from my neighbors that I have to allow their water to come onto my property. I put french drains onto my property But the amount of water coming from theirs is flooding my yard and spreading into my second level home!!! Shouldn't my neighbors try to stop water coming upon their property like I did!!

    • You install a hardscape of larger rock in the area the water runs. Think of it as a stream bed. It's IMPOSSIBLE to stop water from running across your land or your neighbor's land. All water is trying to get back to the seven oceans. It is ILLEGAL to divert water from land in a way that it's now going a direction it wouldn't go PRIOR to the development of the land.

  2. For soil around the foundation of an existing house - what's the appropriate soil composition (i.e. how much clay, gravel, etc. should be mixed together)? Thanks.

  3. I live at the bottom of a hill. When tropical storm Lee came through our area a few years ago, I ended up with 39 inches of water in my finished basement. (It's no longer finished). Since then I've noticed than when it rains I have water seepage in different parts of the basement. I had a plumber come by to give me an estimate for a sump pump, but he said until I fix the grading problem around around my house a sump pump wouldn't help as water ponds in my yard when there is a heavy rain. I don't understand. Could you possibly explain what the plumber might have meant?

  4. we are having a new house built and the construction crew is dumping all kinds of broken cement tile roofing , rocks and broken bricks, I asked them to remove the piles , I am afraid they will try to grade these items into our foundation, I think it will be harmful to our foundation, Am I correct ?

    • Yes. TAKE PHOTOS and document this and any other apparent error. Put your complaint in WRITING NOW to the builder. ALL complaints and issues MUST be presented to the builder in writing and produce written minutes of every meeting with the builder.

  5. I need to coorect improper grading around my foundation. The existing dirt slopes inward towards the basement and water is getting in at the joint of the basement floor and basement walls. What kind of dirt do you recommend I get to fix this? Thank you.

  6. We has an elevated yard, which causing the water to flow toward our house and the gate. The grass from middle of the yard to our house is pretty damage/muddy all the time. I contacted the builder and he replied 'the area is extremely shaded from being covered by the house and does not allow much sunshine. Unfortunately, there would not be anything that we could do to fix this.' Can't they put in a French drain by the house or something? Is there anything we can do? It's our first house and I feel cheated as the neighbor had they fixed before moving in.

  7. Have a house one wall bricks sets foundation about 1inch inside move in put carpet down filled it but on north side of house when it rained real bad bedroom leaked on floor will that empty space fill with water.house bilt in1975

  8. What's the mathematical way to figure out how much dirt will be coming out of hole for my house

    And how do you change the elevation numbers to feet by having the undercuts

  9. I have a new property where the driveway and frontof lot slopes toward new house spot. New house spot is now occupied by a 40x60 pole barn that will be relocated. I want to enlarge the exisisting barn earth pad to accomodate house foundation. Since part ofthe the spot has been compacted over decades from farm equipment what composition of fill is best to create a stable and well drained situation? Note my plan for drainage includes 2 swales i stalled uphill for redirect.

  10. We have an older house with a crawl space under it. We have water coming in under the footing/foundation. We have checked for broken pipes and leaks. None found. We have been pumping the water out from under the house. Any thoughts as to what can be done with this problem?

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