Crawl Space Waterproofing: Hydrostatic Pressure, Sump Pumps, and Interior French Drains

If you are having water in your crawl space, then you have come to the right place. We are here to guide you through every thing you need to know. First and foremost, the term crawl space waterproofing is kind of a white lie. The systems typically installed should actually be called water management systems. This is due to the fact that the crawl space it self is not waterproof at all.

Water is still coming into the crawlspace, whether below the footer or through a small hole in the foundation. Once the water enters into the crawl space, it is properly directed and removed. The two typically installed water management systems are interior french drain systems, and/or a sump pump. However, before we get into the systems we must talk about where the water in your crawl space is coming from.

To answer this question we must first define the term Hydrostatic Pressure. Hydrostatic Pressure is a phrase that you may have heard talked about before, but what is hydrostatic pressure? Hydrostatic pressure is the pressure being applied to groundwater, and then this pressurized water forces itself into cracks/crevices of your foundation, and even under the footer of of your foundation as well. Thus allowing water to infiltrate inside your crawl space. Any water management system used is typically focused on managing the water coming from hydrostatic pressure.

The first system we will cover is the sump pump. You may have heard of a sump pump before or you may not have. Either way we are going to go over everything you need to know when it comes to sump pumps. There are 3 parts to a good sump pump installation.

1. A proper sump pump basin/pit. The sump pump basin is typically 24-30 inches deep and is installed directly flush to the top of the soil. Holes are drilled directly into the sides and bottom of the pit itself this allows any water to properly flow into the pit.

2. The second part of a sump pump installation is the pump itself. A sump pump is just a phrase used to describe a water pump installed into a basin and is used to catch ground water. While there are multiple styles of sump pumps, we are going to focus on the submersible pump. This is a style of sump pump that sits safely and directly in the water that it is pumping out.

3. The final part of a sump pump installation is the discharge line. This is typically made of 1.5-inch PVC and is used to direct all the water being pumped out of your home.

Now that we have gone over the components of a sump pump, lets dive deeper into the pros and cons of a sump pump. The #1 pro of a sump pump is its ability to catch water from a small low region of a crawl space. It is highly effective at catching smaller amounts of water primarily from one low spot in a crawl space. This leads directly to its biggest con or limitation.

It is unable to catch all the groundwater from under your crawl space. It is installed typically in one corner of the crawl space. So, its physical location limits the amount of water it can effectively manage/pump out. Now if your home only has one area of standing water during a rainfall, then a sump pump is probably a great option for you! If not, then keep reading below.

A french drain system is a much more extensive and complete water management system. It has 3 components as well. The 3 components being a 4-inch corrugated/perforated pipe, an aggregate of surrounding the pipe (typically gravel), and a sump pump that is used to catch all the water from the pipes. While we mentioned the main limitation of the sump pump is it cannot be physically throughout the whole crawl space, the french drain system can be.

The first step with an interior french drain system is to trench all along the base of the foundation inside the crawl space (also called the footer). The pipe is then installed, and gravel is installed completely encasing the pipe itself. The gravel allows water to flow and helps prevent the pipe from clogging. The piping is then channeled to the sump pump, and appropriately pumped out of the crawl space. This system can last for years if professionally installed and is highly effective at catching water that makes it into your crawl space.