Water In Crawl Space: Causes and How To Fix

Water in the crawl space of your home may not seem like a big deal, but it can cause major damage. Though this issue may be out of sight, keeping it out of mind is a big mistake.

Left unchecked, water in a crawl space can cause mold growth that can make the air quality in the home above dangerously unsafe. It can also lead to rot in the framing of your home, weakening its structural integrity and eventually requiring expensive repairs.

Moisture also attracts all manner of pests, including wood-destroying termites and carpenter ants, as well as rats and mice. And, if you’re trying to sell the home, a pool of water in your crawl space is enough to scare away most potential buyers.

Luckily, there are ways to nip this problem in the bud before it becomes a major issue. In this article, we’ll look at what causes water to pool in the crawl space and review methods for fixing this issue. We’ll also provide step-by-step instructions for installing a drainage system in your crawl space.

Water In Crawl Space

What Are the Causes of Water in Crawl Space?

There are several reasons why water might be collecting in the crawl space beneath your home. While some are easy to fix, such as a clogged drain or leaky pipe, others may require a pro to get the moisture problem under control. In the section below, we’ll review the most common reasons water is collecting in your basement.

Improper Grading

Water can make its way into the crawl space from rainwater due to poor grading or even landscaping. If the ground around the foundation is not graded away, it can cause water to infiltrate the foundation and enter the crawl space, creating problems.

If water gets deep enough around the foundation, it can even access the crawl space via the vents in the foundation. To determine if the problem is improper grading, check the grading around the foundation during heavy rain to see if water is pulling against the foundation’s base.

Foundation Vents or windows

Many foundations have vents and windows built into them. While both are vital for allowing light and fresh air into the crawl space, they can also be places water can infiltrate. This occurs if water is allowed to collect around a vent or in the window well.

Check these areas during or right after heavy rain to see if water is accumulating. Protect window or vent wells with a cover that shields them from rain and make sure the ground around them directs water away.

Cracks in Foundation

Houses settle over time, which causes cracks to form in the foundation. These cracks, if large enough, can allow water from the soil to pass through after heavy rain, leaking into a crawl space.

While there is no way to prevent these cracks from forming, you can repair them with a good concrete cement patch, available at your local home improvement store. You should also check the grading and gutters around the home to make sure water isn’t pooling around the foundation.

Leaking Pipe

Climb into your crawl space and you’ll more than likely find the supply lines and drain lines that make up your home’s plumbing running along the floor joists of the home. As a home settles, it can put stress on these pipes, causing cracks or breaks in the joints that create leaks.

Even a moderate drip can quickly collect in the crawl space, causing problems. Repair the leaky plumbing right away to eliminate the problem.

Clogged Drain

During torrential rains, the drain systems around your home can become overwhelmed, causing water to backflow toward your home’s foundation, where it can infiltrate the crawl space through cracks or vents.

Making sure the drains around your home are clear of leaves and other debris will help to prevent this problem. While this may fix the issue, if the drainage system is still overwhelmed during heavy rain, there’s little else you can do to prevent that water from coming into your home.

In this case, you’ll need to install a drainage system in your crawl space to ensure water isn’t allowed to remain there once the storm is over.

Why Should You Eliminate Moisture in Crawl Space?

How to Keep Crawl Space Dry
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While it may be tempting to ignore water collecting in a part of your home you don’t often visit, doing so could be tragic. Water in the crawl space can result in mold problems that can negatively impact the water quality in your home to structural problems that can lead to expensive repairs to your home’s framing.


Even a small amount of water accumulating in your crawls space is not something you should ignore. If any amount of moisture is allowed to linger in your crawl space, it quickly becomes a breeding ground for mold, posing a serious health hazard to you and your family.

Mold releases toxic spores that can float into the living space above, triggering asthma, bronchitis, and migraines and irritating the eyes.

Structural Damage

When water collects in a crawl space, it can cause the timbers that make up the home’s framing to become wet.

That wet wood will eventually rot, causing serious structural damage. Structural damage to a home’s foundation or framing is very costly to fix, making it crucial that you address any water in your crawl space immediately.


Many pests are attracted to water. Water that is allowed to collect in a crawl space creates a perfect environment for attracting these pests.

Termites and carpenter ants, which can devastate a home’s framing if allowed to infest the home, are attracted to moisture, as are rodents and other animals.

Selling a home

Don’t expect to sell your home if there’s water in the crawl space. Most buyers don’t want to inherit your crawl space’s water problem. Even if they’re happy to take on the issue when they move in, many banks won’t approve a loan for a home with water in the crawl space until that issue is fixed.

How to Keep Crawl Space Dry

While the problems water can create in a crawl space should be alarming to any homeowner. Fortunately, there are ways to fix the problem, many (but not all) of which can be completed with the need for an expensive professional service.


Encapsulating a crawl space involves installing a vapor barrier that consists of thick plastic sheeting. When done properly, the plastic sheeting creates a tight seal to the foundation wall and any supports, ensuring that water vapor and moisture from the ground aren’t allowed into the space.

Encapsulation sometimes involves the installation of a dehumidifier, which removes moist air from the crawl space, preventing condensation from forming.

Sump Pump

When it’s impossible to completely prevent water from getting into your crawl space, you can at least ensure it won’t spend much time there by installing a sump pump. A sump pump sits in a basin in your crawl space.

As water enters the space, it’s directed into the sump basin, where the pump sends it through a drain pipe to a location outside and away from the foundation of your home. Sump pumps are conveniently designed to turn on when water reaches a certain level inside the basin and turn off when the basin is empty.


Ventilation helps improve airflow through the crawl space, which causes water to evaporate. Make sure your foundation has ample venting to create this ventilation. You can also further expedite the evaporation process by installing a dehumidifier in the crawl space to dry out the air.


If water is getting into the crawl space from the outside, consider waterproofing it. Although this can be costly, creating a waterproof barrier similar to encapsulating a crawlspace will ensure water can’t get in, even during heavy rains. Make sure to waterproof both the interior and exterior of the foundation if you go this route.

How to Remove Water From Crawl Space

How to Remove Water From Crawl Space
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If the cause of water in the crawl space is due to a structural or plumbing issue, the solution is simple. Fix the broken drain or supply line that’s leaking into the water. If water is directed toward your home’s foundation, remedy the problem by grading around the home so rainwater is directed away.

Sometimes these methods aren’t enough to keep water from entering the crawl space during periods of heavy rain. In this case, the solution may not be to prevent water from getting in but to be sure that it can drain out quickly when the storm is over, preventing it from pooling in the space.

While it may be necessary to hire a pro, sometimes this is a job you can complete on your own if you’re willing to put in the work.

For any job that requires entering the crawl space, it’s important to take the necessary safety precautions. Before entering your crawl space, you should wear clothing that covers your entire body, preferably coveralls. Since the air under a crawl space can be potentially harmful, wear a respirator.

If you spot mold growth in your crawl space, it’s best to call in the professionals as remediating the problem requires special gear and expertise most homeowners don’t have.

Step 1. Remove Vapor Barrier

To install a drainage system for your crawl space, you’ll first need to get any vapor barrier on the crawl space floor out of the way. Carefully remove the plastic sheeting and roll it up.

Step 2: Dig a Hole for the Sump Basin

You’ll need to dig a hole for the sump basin. It’s crucial that the basin be installed at the lowest point in the crawl space to ensure it collects any water that finds its way into the crawl space as effectively as possible.

This is the most difficult part of the job as you’ll need to dig a hole large enough to support the sump basin, most of which measure around 2 feet deep and 18 inches in diameter. Prep the basin by drilling 3-inch holes in the sides for the perforated drain pipes you’ll install in the next step.

When digging the hole, leave enough space below and around the basin for rock aggregate. Add several inches of aggregate at the bottom of the hole before installing the basin.

Step 3. Dig a Trench

You’ll need to create a space in the crawl space for water to run to so it doesn’t pool in the space. Dig a trench along the foundation wall no closer than 12 inches to the wall. Disturbing the ground near the base of the foundation can cause structural problems. A good rule of thumb is to keep the trench the same distance from the foundation as its height.

You’ll need to dig the trench 4 or 5 inches deep and three inches wide to support the 3-inch pipe and create enough space above it for aggregate.

Step 3. Lay Perforated Pipe

Apply a layer of aggregate in the trench, then lay a 3-inch perforated pipe in the trench. The aggregate will help drain any water that passes through the pipe.

Placing the pipe near the foundation wall will catch any water that seeps in through cracks, vents, or other openings, preventing it from making its way further into the crawl space where it can pool. Make sure the pipe is an inch or two below the rim of the trench.

The pipe should run into the sides of the sump pump basic, directing any water it collects to the pump, so it can be removed via the pump’s drainage pipe.

Step 4. Cover Pipe with Gravel

Cover the pipe with aggregate to help the drainage process and ensure the plastic pipe stays inside the trench.

Step 5. Install a GFCI Outlet

If there’s no existing GFCi outlet in your crawl space to power the sump pump, you’ll need to hire an electrician to install one. This is one step that requires a professional. Make sure the outlet is close enough to the sump pump basin to power the pump that will go inside it.

Step 6. Install Sump Pump

Once the sump pump basin, drain pipe, and GFCi outlet are installed, you can add the sump pump by simply resting it inside the basin.

Step 7. Install Drainage Pipe.

The sump pump needs to send the water to your home’s exterior, so you’ll need to install a drain pipe. Install a length of Schedule 40 PVC pipe to the discharge side of the sump pump and run it through one of the holes in the sump pump cover.

The sump pump works by discharging water that accumulates in the basin through the drain pipe. Run the drain pipe through the sump pump cover and attach it to the basin. Secure the pump cover with the included fasteners.

Attach it to a PVC drain pipe and run the discharge pipe through the wall just above the foundation.

Local codes usually require a sump basin to be vented. To vent the basin, install a second pipe from a second hole in the sump basin lid.

Run the plumbing for both vent and discharge along the floor joists, then through the rim joist by drilling holes in the joists that are large enough to accommodate each pipe.

Step 8. Direct Discharge away from the House

Now that the sump pump and vent and drain pipes are installed, you’ll need to make any necessary attachments to the drainpipe to ensure the water is directed away from home so it doesn’t end up back in the crawl space.

If possible, tie the discharge pipe in with the gutter drainage system.

Step 9. Install Additional Aggregate

Cover the area around the drain line and the sump pump basin with aggregate, which will help water pass through the drain pipe and basin, so it drains more quickly.

Is Water in My Crawl Space After a Heavy Rain Normal?

While it’s not uncommon to have water end up in a home’s crawl space following heavy rain, allowing it to pool there for an extended period, more than a day or so, can cause serious damage in the form of rot and mold also potentially attracting pests.

Eliminate the issue by first checking gutters around the home to make sure they are draining properly and directing water away from home. If the gutters check out, survey the grading around your home’s foundation to ensure it’s not directing water towards the foundation.

If both the gutters and foundation are okay, you may need to add a drainage system in the crawl space, detailed in the instructions above.

Can I Eliminate Water in My Crawl Space Myself?

As with many projects inside the home, this is something you may be able to tackle yourself, depending on the severity of the situation. If heavy rains cause moderate flooding in your crawl space, address the issue by repairing gutters or even installing a fairly simple drainage system following the directions above.

Keep in mind that many projects require the installation of a sump pump or dehumidifier, which means you may need to have a GFCI electrical outlet installed, a job that requires a licensed electrician.

If the rain is causing more serious flooding, you’ll need to call in a professional to develop a more sophisticated solution before it creates structural problems or mold issues in your crawl space.

While hiring a professional can be costly, it’s still much cheaper than the cost of structural repairs to your home’s framing.

Can I Sell a House With Water in the Crawl Space?

It is possible to sell a home with water in the crawl space in most states as long as the seller discloses the problem on a property disclosure statement. Failure to do so could open you up to legal problems if the buyer discovers the issue after the sale. Even if it doesn’t, it’s the right thing to do.

The seller can provide a credit for the issue at the sale if they don’t have the financial means to fix it before closing.

Keep in mind that though the buyer may be okay with purchasing a home that has a drainage issue in the crawl space, the bank lending them the money may not be, especially if there is a concern that the issue is causing structural or mold problems.

And, of course, dealing with the problem before putting the home on the market will almost certainly make it easier to sell.

How Much Does It Cost to Encapsulate a Crawl Space?

Encapsulating a crawl space, which involves installing a drainage system with a sump pump and sump pump basin along with a dehumidifier, if needed, can be costly if you plan on hiring a professional service to do it.

Most homeowners will spend an average of $5,500 to install a crawl space encapsulation system. The cost can vary from as little as $1,500 for installing a simple plastic barrier to as much as $15,000 for installing a complete drainage system with a sump pump and dehumidifier.

Of course, doing such a project yourself is much more affordable. A 20-mil vapor barrier costs just 50 cents to 70 cents per square foot, while a sump pump runs between $60 and $170, with a simple sump pump basin costing around $30.

Dehumidifiers represent the costliest part of encapsulating a crawl space with a price tag of between $800 and $1,200, according to Home Advisor.


While you shouldn’t panic at the sight of water in your home’s crawl space, you shouldn’t ignore the problem either. As we discussed above, when you allow water to pool in the crawl space under your home, it can wreak havoc in the form of rot, mold, and pest infestations.

Fixing this problem before it causes major structural problems that cost thousands of dollars to repair or a pest infestation that requires the services of an expensive exterminator. The solution may be as simple as unclogging the house’s gutters and downspouts or repairing a leaky pipe or it might require the installation of a drainage system, a job you can do yourself or hire a pro to complete.

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Written By: Yevgen

YevgenI'm a DIY nut, and the founder and chief editor here at Weekend Builds.
This site is a result of my DIY passion, and to share the joys I have experienced fixing, building, and creating things over the years.

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