Do you have water coming into the house or pooling close to the foundation because of a sloping concrete porch? Do you want to know how to fix this problem? You’ve come to the right place, for we have researched this question and found the answer for you.
There are several ways to fix the issue. The most common solution to a sloping porch is to install a channel drain on the lowest part of the slope. Here are other methods that can solve the negative grade issue.
- Catch basin at the lowest spot
- Overlay existing concrete
- Replace the concrete slab
Let’s talk more about negative grade in the succeeding sections. Learn more about the different ways to solve a negative grade problem in the sections below, including the pros and cons of each.
What is a negative grade?
A negative grade is when the surface around a structure slope towards the structure. In the case of a concrete porch, the surface of the porch slopes towards the house.
Negative grades aren't limited to porches, and can even be found in driveways or landscaping. If you have any area around your house where water pools after rain, that area has a negative grade.
What is the ideal slope?
Ideally, there should be a quarter of an inch of slope away from the house for every foot of length. Thus, if you have a 12-foot driveway, the starting point of the driveway should be 3 inches higher than the ending point.
A concrete porch should have a similar slope.
When measuring the length, use the length of the surface that is going away from the house.
Check your local code regarding the slope for porches.
Negative Effects Of Negative Grade
A negative grade leads to the accumulation of water around the house. This water buildup can lead to serious negative effects.
If your house has a basement, strong rains can cause basement flooding.
Concrete is a porous material, and water will pass through it over time.
This will create moist areas in the wall and floor of the basement. If you get rain for an extended period, the soil around the basement will get saturated and push water through.
Anywhere there is moisture, there will be mold.
Water that accumulates around the house will create an area of high moisture. This area becomes an ideal habitat for mold growth.
Constant exposure to water will cause the soil to soften. Eventually, the ground under the foundation will sink. Once the ground sinks, the foundation will also sink.
Additionally, concrete surfaces that are constantly soaked in water will weaken and crack over time. The surface of your concrete porch can have water damage due to the negative grade.
Surfaces that have pooling water are a slipping hazard. This is especially true if the surfaces have started to develop mold.
Any high-traffic area—like the porch—should always stay dry because the areas with water will always be an accident just waiting to happen.
How to fix a concrete porch that slopes toward the house?
There are several different solutions to a concrete porch with a negative grade. All these solutions seek to move the water away from the house—and with it, the foundation.
Let’s talk about each solution in more detail below.
A channel drain, also known as a trench drain, is commonly a straight drain that runs the length of a problem area.
A channel drain takes advantage of gravity by positioning itself at the lowest point of a surface. Any water that gets to the area doesn’t get the chance to accumulate because it will flow into the channel drain.
A metal grate covers the top of a channel drain. The bottom of a drain ideally slopes to a piping system that will draw water away from the house.
Before you install a channel drain on your concrete porch, you need to identify the lowest point. You can tell where the lowest point is by using a level where the water pools.
Cut the concrete about a foot wide to install the channel drain. Slope the drain to a pipe system that you can connect to the closest drain.
The advantage of a channel drain is that it can drain water from a wide area, making it extra effective against water accumulation.
The disadvantage of a channel drain is that it can be hard to match the metal grate with the look of your porch. Additionally, if the lowest point is somewhere in the middle of the porch floor, then having a channel drain there can ruin the look of your porch.
A channel drain can also attract pests.
A catch basin is a common drainage system that you’d find in landscaping. The top has a metal grate that covers the pit. The bottom has a pipe that redirects water to the drain.
This is a useful solution if the water on your porch accumulates in a small area only.
The installation of a catch basin is similar to the installation of a channel drain. The first step is to locate the lowest point. Cut the concrete at the lowest point and dig a hole in the ground.
Install a sump pit into the hole. Connect a pipe from the sump pit to the nearest drainpipe.
The advantage of this method is that a catch basin is smaller than a channel drain and can easily blend with the rest of your porch. This method is also the most ideal if the lowest point of the porch floor is somewhere in the middle.
A disadvantage of a catch basin is that it can attract pests. Moreover, if the water flow is too heavy, the pipe leading out of the sump pit might not be able to drain fast enough. This can happen if the catch basin catches garbage from the porch that can clog the pipes.
Overlaying concrete is installing a new layer of concrete over the existing concrete. This will allow you to correct the negative grade and create a slope that leads away from the house.
Before you install a new layer of concrete, you need to fix any cracks in the old concrete and let the repair dry completely. If your porch accumulates water due to a negative grade, it can have cracks from water damage.
Once the repairs are complete, clean the old concrete surface thoroughly.
Use self-leveling concrete to make it easier for you to overlay your existing concrete. Follow the manufacturer’s instructions when mixing and pouring the concrete.
Measure the slope that you need so that water will no longer flow toward the house.
The advantage of this method is that you will be able to fix the slope issue while rejuvenating the look of your porch. Additionally, this is the easiest and cheapest solution to the problem.
On the other hand, the disadvantage of this method is that the floor level of the porch might become higher than the floor level of the house. This might be against the building code in many places if the porch is adjacent to the house. Check your local building codes regarding this.
Replace the Concrete Slab
If the concrete base of the porch has a lot of damage due to exposure to water, it might be better to remove the old concrete slab and pour a new one. Additionally, if the concrete has a negative grade because part of it sunk over time, then you might want to fix the layer under the concrete slab to stop the concrete slab from sinking any further. There could be a problem with the subgrade that led to the sinking of concrete.
In these scenarios, you will have to remove the old slab to fix the issues under it.
Once you decide to go this route, you need to decide if this is something that you are willing to do yourself or whether it is something you’d rather have a contractor do for you.
The advantage of this method is that this will solve all the underlying issues of having a negative grade. Additionally, this method will ensure that your patio is compliant with any local building code in your area.
The biggest disadvantage of this method is that it can easily become the most expensive of the methods on this list. The price will rise even more if you need to bring in a contractor for the job.
There are different ways to fix the negative grade on your porch. Choose a solution that is most applicable to your situation.
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