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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29 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.

    • MOSS IT OUT!
      In your situation, Hypnum moss would be the answer, I think.
      Hypnum is tolerant of constant wetness, it's one of the most inexpensive mosses, and also one of the fastest spreading.

      Because it's a Pleurocarp (one of the two types of mosses), it can be placed in patches all over the area.

      DON'T do the milkshake thing. It doesn't work. It never worked. I think it was a prank someone pulled to get people to spray buttermilk everywhere.

      You can order it online fairly cheaply. Or, and of course you can't do this because it's probably against regulations, just take a bag with you when you go to the park. I can almost promise you that just off the beaten path, there's Hypnum everywhere.

      While you're (not) doing this, however, please don't take more than 25% of the patches you see. Moss holds moisture for the plants growing nearby and prevents invasion of competition. Don't take more than 25%, and don't take any if there isn't at least a square foot patch (there will be you just have to look).

      You can take patches of moss-covered deadwood too, but it may be a different species so it might not be as tolerant of the conditions. Doesn't hurt to bring it to the area, though.

      I used different mosses to solve a problem with topsoil erosion on the shady side of my house - which were rather pressing since I live on a terraced lot and there are three 4' staggered walls on the downslope as opposed to one 12' retaining wall. Worked like a charm and I've collected several species and am cultivating it on the uphill retaining wall and various pieces of decorative deadwood as well.

      Not a moss expert, but not a novice - and that's my 2 cents.

  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?

    • I got you. My kitchen is an add-on and has crawl space under it so I have a teeny bit of experience with this.

      First step (inexpensive):
      Ensure that rainwater from your roof isn't contributing to the problem. Make sure the gutter spouts are driving roof rainwater far enough away from your house, and in the right direction, that the rainwater isn't coming right back towards the foundation. If not, get some hoses or trays (trays can look nice if done properly). And I know it's no fun, but we have to clean those gutters twice a year.

      Second step (inexpensive):
      Ensure the water isn't gaining access the through the crawl space access hole. This is where my experience took place, because when I bought my house everything was fine but a year later there was an insane amount of humidity in the summer that my dehumidifier could not conquer.

      Turns out the access hole to my add-on kitchen's footing, concealed by the backyard deck, had been covered with a very poor quality plywood which had warped and rotted and essentially let nature have free access to my basement. At least it was a few inches above ground level so there was no rainwater entering, but BATS SURE DID! (I mean... I love bats. They eat mosquitoes, and I grew up in the country with a barn so it's nostalgic to have them around at night - BUT NOT IN MY HOUSE!)

      So... yeah - check the access holes. Make sure they're sealed properly.

      Step three (inexpensive if you're patient):
      Correct the grading around your home's footing. As far as I know, all of the same rules apply. If you're patient and wait for sales, or if you buy ripped bags (50% off at most box stores), you can buy silt, clay, and rocks fairly cheaply. Dig away the topsoil in sheets (as best you can), throw down the mix, tamp it so it slopes away (fairly sharply) from your home, replace the sheets of soil.

      Or consider buying 4" perforated drainpipe and put it in under the ground near your house (after wrapping it with landscape fabric). It will essentially make an underground moat for your house and divert water flow to wherever it leads.

      Nothing wrong with having a tiny hill next to your house. I have one on the East side of mine because the driveway is close by and no thank you I do not want an entire driveway's worth of rainwater getting shoved into my foundation.

      So those are the first three steps. 1 and 2 might solve your problem. I hope they do because they're cheap and not too labor-intensive.

      Step 4 (not all that expensive):
      Crawl spaces need to be moisture controlled. The best way to do this is to prevent the water from ever getting in, but it will sometimes. I don't have much knowledge with this, but I believe the standard is to lay down a few inches of gravel, then cover with thick plastic sheeting SEALED to each other and to the walls a few inches up.

      This is a fix for crawl spaces that don't see much traffic, because crawling around on plastic on top of gravel will damage the plastic, but there are tapes that will survive moisture.


      Even without plastic sheets, the ground under your house should be covered with gravel. Just the gravel alone prevents an insane amount of moisture from reaching your floor, because the moisture rising from the dirt beneath it is blocked or condenses back down.

      It doesn't have to be official "gravel". Any small stone is fine. This is something you can usually find for free on Craigslist (if you haul it away) every now and then. If it's too much of a job to do all at once or you don't have a truck, get a sturdy rubber/plastic tote from Wal-Mart and get it filled occasionally with the free stuff. Or keep an eye out for those torn bags at home depot and get a $4 bag of pea pebbles / river gravel / heritage stones / pea gravel / paver gravel / etc for $2. (I bought 2 bags of pea gravel, 2 bags of pine bark nuggets, and a bag of heritage stones from the 50% off "torn bag" cart earlier today to cut into my potting mixes).

      And because I have to get going - step 5+:
      Waterproof / hire a professional. Full-on waterproofing (youtube vids for instruction) or hiring a pro. If you hire, get someone highly reviewed. If you're still nimble, watch a bunch of youtube vids and do it yourself. Get a good respirator, those surgeon mask things are crap.

      Good luck!

      It's easy to be long-winded when you type 70 words per minute.

  11. What about the opposite situation, too much grade? I'm looking at a house situated 14 feet from it's closest corner at a grade of 15%, to a culvert/stream bank that steeply drops from there in about 8 feet to the water which is about 8 feet down.
    Even though it is in a no flood zone, my realtor recommends against buying it because of possible foundation damage as seasons alternate between wet and dry and the foundation gets stressed.
    Any ideas would be much appreciated.

  12. Hey tim have a question i know my slope on my soil isnt good and i have standing water against the vinyl siding of my house should i have a minimum of 6 inches from the top of my foundation to any soil all around my house if so say my foundation is 4 inches thick would you just keep it at the bottom of the foundation? Thanks

  13. How high can the ground be against a single brick home with no basement? I dug down towards the bottom of the last row of bricks and the gravel started to appear. There is still a row of bricks showing though. I am concerned about grading and bug control.

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