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How To Waterproof Your Crawlspace

Updated on June 19, 2013

Water is a major cause of damage to a house causing millions of dollars in damage every year. While some of this is unavoidable, there are precautions you can take to lessen the effects of water damage over the years. Water under the house can cause floor joists to rot, attract termites, and let mold grow rampant. Keeping the crawlspace dry can save many future headaches.

Start With Some Landscaping

The yard should be sloped away from the house so the water runs downhill instead of under the crawlspace. The gutters should drain properly while the downspouts should divert the water away from the house. This alone should keep the majority of the water clear of your home. Small water absorbing plants should be planted around the edges of the house. Keep trees at a distant because they can cause cracks in the foundation as well as roof damage.

Coat The Outside Foundation

Use a quality non-fibered roof and foundation coating to seal the outside of the foundation. This is mess and needs to be applied with a brush. Put the coating on fairly thick to help keep water from seeping through. When applying the tar take your time and go slow. Be careful not to brush it on the siding or on the yard. It is very hard to clean off. Dispose of the empty containers as noted on the product.

Under The House

The inside walls need to be coated with a waterproofing made for concrete, like Drylock or other similar brands. This is not as messy as the outside tar however it is a lot harder to do. There is not much room and a lot of the work will need to be done while lying on your belly. A lot of breaks are necessary and even a lot of volunteers could be helpful.

Still Under The House

This next step can be a help or under the right conditions lead to a disaster. Dragging large sheets of six mil plastic under the crawlspace is what you will be doing. The ground needs to be totally covered while the edges are sealed to the inside foundation walls with some leftover tar. This is supposed to keep ground moisture from seeping into the house. the problem here is if you ever have a plumbing leak it will be almost impossible to get it dried out under there without removing all the plastic.

Foundation Vents

Foundation vents need to be opened and closed in places that have freezing temperatures one season and hot another. Some recommend automatic vents but these can malfunction quite easily. The vents need to be opened in the spring and closed in the autumn. The vents need to be shut during the winter to help hold the heat under the house to keep water pipes from freezing. In the summer they need opened to help keep the ground dried out under the house. Your whole house needs checked twice a year and foundation vents should be on this list.

Crawl Space Area

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The foundation will need a good cleaning before applying the foundation coating. Rent a high pressure washer with a good detergent to spray the foundation with. After a good cleaning a good rinsing will need to be done. Allow to dry completely before applying the tar. You will need to apply two coats for best results. Coverage should be about 100 square feet per gallon for the first coating and 200 square feet per gallon for the second coat. Drylock and other types of masonry sealers usually cover about 200 square feet per gallon. Now waterproof your crawl space for the life of your home.


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    • kennynext profile image

      kennynext 4 years ago from Everywhere

      Thanks Eiddwen. Taking time to do preventive work can save thousands of dollars in the future. Have a great great week

    • Eiddwen profile image

      Eiddwen 4 years ago from Wales

      Interesting and so well informed. Voted up and shared.