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Does a Waterproofed Basement Need a Sump Pump?

We all agree that basements are vulnerable to flooding. Whether this is from the effects of Mother Nature or thanks to rusted piping, preventative measures have to be taken. In unfinished basements, a sump pump is the go-to method. But when the space is finished nicely, a sump pump looks out of place.

Finished basements are waterproofed, which might seem like the solution. However, while waterproofing and sump pump both keep basements dry, they do so in different ways that don’t really overlap. Now, you don’t have to install the sump pump, but you should make that decision once fully informed.


Waterproofing prevents seepage through walls and floors. Sump pumps remove standing water from excessive seepage, burst pipes, floods, etc. Waterproofing cannot help against floods or burst pipes but sump pumps are not necessary with waterproofing. The flood risk and potential damage must be considered.

Purpose of Waterproofing

Waterproofing has been developed to prevent water from insidiously infiltrating an area. 

This is done through a watertight material being laid over a surface. This material is usually plastic-based.

Plastic materials are impermeable; the pores between the molecules are too small for water to get through. 

Sheet Waterproofing Membrane and Liquid Waterproofing Membrane

Waterproofing materials include thin sheets as well as liquids that can be applied to various surfaces. 

Some waterproofing materials also allow for breathability. Because water is usually trapped within the membrane, an exit for evaporated water can prevent water damage from trapped water. 

As the purpose of waterproofing is to keep seeping water out, it can have many advantages. However, eliminating the need for a sump pump is not considered to be one of these advantages.

Waterproofing is good for controlling humidity and small amounts of water leaking through, but once water gets into the basement, whether this is through a faulty waterproofing barrier or water entering through areas that are not waterproofed, the water cannot leave.

When your basement is flooded without waterproofing, some of the water can soak into the ground beneath the basement. 

So, this is when waterproofing can prove to be disadvantageous and why sump pumps remain important.

Sump Pumps Have a Different Purpose

Rather than keeping water out—or in—sump pumps remove water from an area, most often the basement. 

Sump pumps consist of a containment unit underground and a system of pipes that move water outside of the house. 

REPLACE WITH LICENSED IMAGE

Water collects underground and is removed from the containment unit when the water reaches a certain level. 

The goal of the sump pump is to keep the water level at this level or below. 

There is also a level above this one that indicates that the sump pump is not removing enough water. At this higher level, the sump pump will sound an alarm so that you know to intervene before the problem becomes overwhelming. 

Where a waterproofing material is made to control small amounts of water, sump pumps are made to control large amounts of water. 

If you have a problem with humidity or condensation in your basement, a sump pump will not solve this problem. It will only solve problems related to flooding and standing water. 

The level at which a sump pump becomes effective is not specified, but a few inches of water is most likely when a sump pump will begin its work based on how they work. 

Seepage Can Create Standing Water

Determining where water is coming from and how much is entering can determine whether you need waterproofing, a sump pump, or both. 

For example, if the problem is seepage through the walls and floor of your basement, you may need either waterproofing or a sump pump, but not necessarily both. 

Seepage into the basement can occur due to a variety of factors. 

The soil surrounding your basement can play a part.

If the soil is sandier, the water is unlikely to sit in the soil since the spaces between the sand particles are large enough to allow for water to escape downwards. 

However, if the soil is more clay-based, the water is more likely to stay in the soil because the spaces between the clay particles are small and less likely to allow water to escape. 

If your soil has a high clay content, water is more likely to enter your basement. 

Water seepage on a basement due to clay soil in the surrounding

The quality of your foundation can also determine whether water can enter your basement. A poorly-built foundation will allow more water in. 

Another factor that can affect whether or not moisture enters your basement is the weather—obviously. 

Consistent rain will keep the soil wet. Additionally, when spring arrives, and snow melts, the frozen ground will also melt, increasing the likelihood of moisture infiltration. 

However, if your area does not experience frequent rainfall or does not often experience freezing temperatures, you won’t have much to worry about. 

If conditions allow for seepage to occur, you can choose between waterproofing or a sump pump. 

The waterproofing will keep the moisture out, while the sump pump will allow moisture to accumulate until it is removed. 

Both are not needed because waterproofing should not allow any moisture in, making the sump pump useless since the water will never build up enough for the sump pump to activate. 

Consider the Flood Risk at Your Home

If your home is at risk of flooding, both a sump pump and waterproofing may be necessary. 

The reason for this is that waterproofing will help with small amounts of water seepage but catastrophic water infiltration through flooding requires a sump pump to remove the water. 

With these two systems working together, both seepage and flooding can be kept at bay.

Both of these are only really needed if the risk of flooding in your area or in your home is high enough. 

If weather conditions where you are located include the risk of flooding, it would be wise to have both systems in place.

Additionally, if you live in an area where it is possible to have flooding, being located in a low area (a valley, beneath a hill, etc.) can increase the risks of flooding. 

If you live in such an area, certain parts of your home can make flooding more likely. 

For example, if your basement contains a high window that can break in the event of a flood, your basement is far more likely to flood. 

A broken window can provide a convenient opening for water to pour into your basement.

Basement turned children's area with a basement window

However, it isn’t just weather conditions that can lead to flooding. The state of your pipes also can. 

If you have brand new pipes, the risk of them bursting and causing flooding is low (unless they were poorly installed). 

However, if your pipes are quite old, they can be likened to a ticking timebomb and may burst at any moment. 

Additionally, if your home contains polybutylene pipes, these are likely to fail and cause flooding. 

Another source of flooding in the basement is a water heater

If the water heater’s anode rod has corroded enough to be useless, the water heater’s metal interior is likely experiencing corrosion. This corrosion can cause the water heater to burst and the basement to flood. 

Whatever the source of the flooding, if your home is likely to experience flooding at some point in its lifetime, it would be wise to have both a sump pump and a waterproofing barrier.

What Is Stored in the Basement?

Another reason why it is important to have a sump pump if you are likely to experience flooding is because basements can store a variety of things that hold sentimental value or material value. 

Old electronics, new electronics, appliances, power tools, and more can be stored in the basement. In the event of a flood, these things can be ruined. 

Additionally, basements are often the storage place for sentimental items such as holiday decorations or old children’s toys. These items are often sensitive to water and a flood can ruin them. 

A sump pump can keep these stored items safe from harm.

Installed-sump-pump in the basement

Whether the basement is finished or unfinished, removing water quickly and efficiently can also help minimize the repairs to the basement. 

Sources

https://www.westernadvocate.com.au/story/6888438/how-does-a-waterproofing-membrane-work/

https://www.squareone.ca/resource-centres/getting-to-know-your-home/sump-pump

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