Do I Need a Sump Pump If I Have a Vapor Barrier?

The entire purpose of a sump pump is to drain water out of a crawl space. However, if you’ve heard of other waterproofing methods, you might be wondering why you might need so many different waterproofing solutions to keep your crawl space dry. Remember, a good crawl space waterproofing system is made of different pieces that all do their individual part to protect the foundation. 

What a Vapor Barrier Does 

A vapor barrier is a plastic sheet that is used to encapsulate a crawl space. This impermeable barrier can block out water so that it doesn’t enter the crawl space. You might be thinking that a sump pump isn’t needed because you won’t need to drain water if it never gets into the crawl space in the first place. 

However, while it is true that water and water vapor can be stopped with a vapor barrier, the sheets usually aren’t applied to the roof of the crawl space where all the floor joists and insulation is. Water always can find a way to seep through the top of the space, so it’s better to be safe than sorry. 

What a Sump Pump Does 

Besides being there in case water manages to bypass the vapor barrier, the sump pump plays a significant role in draining out groundwater. The groundwater that surrounds the crawl space is still dangerous, even if it doesn’t enter the crawl space itself. This is because of the way it behaves during the winter. 

Because of the freeze-thaw cycle and frost heave, the groundwater around your crawl space can still damage the foundation. The concrete walls outside the crawl space can still deteriorate because the vapor barrier only protects the inside, not the outside. The crawl space posts can still shift about due to soil erosion too, so a sump pump is needed to avoid foundation damage.