A few years ago during spring, we had really wet several weeks where the rain did not stop, and subsequently, lots of our neighbors ended up having water in their basements. Many of us learned that the way our earth was graded around our homes wasn’t adequate, so the question became how to fix negative grading.
Fixing negative grading requires either adding or removing soil from around the foundation of your home. You may have to do a bit of both to achieve a continuous declining grade away from your home. The ideal drop is 1 inch per foot.
There are other considerations too, such as windows with window wells that may need repair and vegetation such as garden beds or grass that abuts the house. In this article, we’ll cover all the different ways you can fix negative grading so that you keep the puddles – not in your basement.
- What Is Grading In Construction
- What is Negative Grading
- What Is the Proper Grading for Land Around the Foundation
- Best Soil for Grading Around House
- How to Fix Negative Grading Around the House
- Other Land Grading Techniques
- How Much Does It Cost to Regrade Around a House?
What Is Grading In Construction
Grading in construction refers to the slope of the earth in relationship to the structure. A negative grade means the earth is sloping downwards toward the structure. A positive grade means the slope runs downward from the structure.
This article specifically refers to the grading around the perimeter of a house or other domestic structure. Grading is often considered within the context of water drainage, as a positive grade is needed to keep water away from home and keep the home dry. A negative grade at any point along a home’s perimeter can result in leaks and significant damage.
What is Negative Grading
Negative grading means that the earth near the perimeter of a structure, in at least one specific area, slopes downwards towards that structure. The grade doesn’t have to be unbroken, and you can still have a negative grade even if the earth immediately next to the structure is raised slightly.
Let’s say the earth against your house drops about an inch per foot up to 5’ away. If the ground then rises significantly several feet beyond, then you have a negative grade. Water will filter down into the earth and find the path of least resistance, which is often through the walls or floor of your home.
The foundation of a home or shed is not waterproof. If you have concrete block walls, they may be covered by tar or some type of impermeable membrane. If so, then you have a measure of protection against water. But even if you have “waterproofed” the foundation of your house, negative grading means that water will eventually settle against your home and find its way in somehow.
Water that constantly sits against your house can ruin the structural integrity of the foundation. It can cause the foundation to shift, eroding soil from beneath. Shifting can cause cracked drywall, uneven floors, and other major problems. Seeping water through a basement can also cause mold. It will start behind your walls, on the concrete walls, behind drywall, and ruin the insulation.
As you can see, the consequences of negative grading can be drastic. Luckily the solution is something within the average homeowner’s capability and is arguably one of the most important aspects of maintaining your home.
What Is the Proper Grading for Land Around the Foundation
Proper grading around a home or other domestic structure means that there is an unbroken, downward slope starting from the structure up to 10’ away from that structure. An adequate grade is 1 inch per foot of grade, at a minimum. The greater the grade, the more effectively water will run away from your home.
The minimum amount of grade you should have, according to the IRC, is 6” of drop for the first 10 feet. This is also referred to as a 5% grade. Although some jurisdictions do provide a maximum grade of 33% due to erosion and diverting too much water towards adjacent structures, there is no maximum.
Some homes are built in such a way that achieving a positive grade is very difficult, such as those built-in low-lying or marshy areas and those that are extremely close together. Luckily, there are solutions for those issues, which the IRC outlines to install drains or swales. We’ll investigate that more later in the article.
Best Soil for Grading Around House
Most fill will work if it is clean. The ideal fill is a mix of silt and clay, which is impermeable enough to divert water away but also has enough gaps so that it won’t hold it against the structure. It is important to avoid very sandy or high clay content soils. Sand will allow water through before draining and only act as a filter, while clay will hold water against the foundation wall.
It is not a good idea to increase your grade with mulch. Most mulch mixes are extremely soft and will absorb water without allowing it to runoff. It will divert water downwards towards your house or just hold it against your foundation walls, where it will eventually find its way through your walls into your home.
Also, avoid gravel or other very porous material. The purpose of positive grading is to provide a slope or ramp for water to travel down. Gravel is like a sieve; water will travel between the cracks to the earth below. While your foundation should have a layer of gravel down to the weeping tile, where it then gets diverted away from your house, you’ll want to avoid overloading your drainage systems and put dirt on top of the gravel.
Other Materials to Use Around a House
If you have landscaping against your home, soil such as black earth and manure mixes are acceptable, provided the grading is up to code. While river rocks and other landscaping rocks are attractive, they could prove too porous and it is better to cover them with a layer of silty/clay soil.
Be careful, however, with gardening mixes that have higher concentrations of materials such as peat, which act as excellent absorbers of water, and are not ideal when it comes to shedding water. A solution is to simply keep a 1’ buffer all around your house with non-porous soil, then begin your
How to Fix Negative Grading Around the House
To fix negative grading around your house, you need to add grading topsoil around the perimeter of your house. First, remove any vegetation or mulch in areas that need grading. Your grade needs to be no less than 1” per foot, up to 10’ from your home. Add topsoil so that you have a continuous slope around your entire home perimeter. Once added, tamp the soil down, add more if needed, then smooth the grade with a metal rake.
Once you’ve added the topsoil and raked it smooth, check to ensure your grade is continuous using something long, flat and level, such as a 2×4 or a 6’ level. Put the edge flat against your house and check for a continuous downward grade. Be sure you have not covered up any siding on your house and that the topsoil has only made contact with your foundation. Ensure there is at least 6” of clearance between soil and siding.
In some instances, removing soil might be more efficient if much of your home is already graded. This should be a second option since removing soil is much more time-consuming than adding. The goal should be to remove soil in all places where a continuous positive grade is interrupted. Simply use a shovel to accomplish this, then tamp and smooth with a metal rake.
When checking for a continuous downward grade, you should be able to visually see the positive grade. Use a 2×4 and rest the edge against your newly graded surface. Stand back. The wood should sit firmly against the earth on all parts. If you can see beneath the wood at any place, rake and tamp until the wood is firm against the ground. Rest a level atop the 2×4 to ensure your grade is positive.
Finally, once you’ve established a positive grade, check to make sure you have a drop of at least 6” per 10 feet – or 1” drop per 20” of run. You can use any level to establish this starting from your foundation and working outwards. Find your level, then you can eyeball if the end of your level is 1” above the ground. Continue that way until you reach 10’ from your home.
Let’s go through the method for positive grading, step by step:
- Walk the perimeter of your house to identify areas that have a negative grade. Use a 2×4 or another flat object like a 4 or 6’ level to gauge grade by laying one end flat against your house, resting it on the earth. Check for level. If it is level or negatively graded, then you need to backfill.
- Remove all vegetation that is touching or within a foot of your house. Also, remove any mulch or decorative stones that might act to suck up water and bring it towards your foundation walls.
- Add grading topsoil against your house in areas that need a positive grade.
- Using a metal rake, pull soil away from the house to achieve a gradient with at least 1” drop for every 20”.
- Compact with a tamper. This is an important step as simply raking and leaving it could result in additional settling over time, ruining the grade.
- Now identify spots that need to have soil removed. These will be areas that already have a positive grade but may have some minor humps that impede water flow.
- Remove fill and use the metal rake to achieve the proper gradient, tamping and raking as necessary.
- Return with your level or flat piece of wood to ensure all areas have a continuous grade up to 10’ beyond your house.
Other Land Grading Techniques
You may be unable to properly grade along your house due to property lines or other obstructions in many instances. In that case, you have alternative options that, while more labor-intensive, can still work to divert water away from your house.
The first option is to simply create a swale. The term “swale” is just a fancy name for a ditch that diverts water away from your house. In tightly-packed neighborhoods, you’ll notice that between houses there is – or should be – a dip in the earth running the length of the homes and leading to a larger drainage ditch. Lacking space along your home, you can run a ditch parallel to your home to an area with positive grading.
If you have space, but your yard is level or negatively sloped, you can make a ditch a couple of feet deep and a foot wide, place a perforated plastic pipe sheathed in mesh at the bottom, and backfill with ¾” clear gravel.
Creating one of these french drains parallel to your home and leading to an area further away to where the grade is positive can help keep your home free of water.
How Much Does It Cost to Regrade Around a House?
Regrading around your home can cost under $1000 if all you need is some more backfill. You’ll pay for a load of earth delivered to your home plus a couple of guys to spread it, tamp it, and grade it to achieve a positive grade of at least 6” per 10’.
If you need to dig out a drain or just create a swale, then you’ll probably be paying for a landscaper to come out with a small backhoe or ditch digger plus several guys to shovel gravel and move dirt. This would be no less than $2000. For larger homes needing a perimeter drain, then you’ll be looking at the cost of over $5000.
Water in your basement can be an extremely frustrating and costly event that many homeowners experience from time to time. The great news is that you can often mitigate that issue by simply adding topsoil.
Even better, the addition – or removal – of topsoil is a cheap solution that just about any homeowner can accomplish with a little time and effort. Just be sure the material you choose to backfill with is clean and clear and won’t hold or let the water filter through. Your local landscaping supply store will be able to direct you in the right direction.
Lastly, positive grading is just one of the many solutions for keeping water away from your home. Proper gutters, downspouts, and footing drains are also critical to creating a dry house. But a dry basement or crawl space starts with positive grading.