A Step-By-Step Guide to Basement Waterproofing

By
Juan Rodriguez
Juan Rodriguez
Juan Rodriguez
  • University of Puerto Rico
  • DeVry University
Juan Rodriguez is a former writer with The Balance who covered large-scale construction. He is an engineer with experience managing and overseeing large civil works construction.
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Updated on 11/20/19

Basement waterproofing can lead to many problems due to insufficient or poor waterproofing. Seepage can cause extensive damages if it is not addressed properly. Sometimes you will try to apply a coat or any other product in the basement when the actual problem comes from the outer walls. Let's see how to waterproof a basement.

01
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Dig Around

Home being dug around by construction worker
Justin Sullivan / Getty Images News / Getty Images

To protect your basement from water, you will need to dig all the outer perimeter of the basement all the way down to the base of the foundation. Having the right product applied over the walls will be key to having a successful waterproofed basement. 

Drainage tiles, gravel or crushed stone drains, perforated pipe, or other approved systems or materials shall be installed at or below the area to be protected and shall discharge by gravity or mechanical means into an approved drainage system.

02
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Check for Cracks

With the excavation completed, clean the wall and check for any cracks or areas causing the water to seep in. If you have detected these issues, apply a coat of hydraulic cement to the walls to stop the leakage. Hydraulic cement will expand as it is curing and with its chemical properties, it will fill in the cracks and voids reducing the probability of leakage.

03
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Apply Sealant

Apply a coat of cement based sealant to all exterior walls. Cement based sealants are easy to apply and can be used over concrete and masonry surfaces. This type of sealant will harden and will close the concrete pores. In case a hairline crack was not fixed in the previous step with hydraulic cement, it will be covered in this procedure.

04
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Apply a Membrane

Install a waterproofing membrane. A heavy coat of the membrane, an asphalt-modified polyurethane material, can be troweled or sprayed on to seal the foundation wall against water from the outside. Elastomeric membranes are made of modified asphalt and exhibit great waterproofing characteristics.

One of the most important benefits of elastomeric membranes is that they can flex and move to accommodate when new cracks occur. Be sure to use a waterproofing product instead of a damp-proofer product that is likely to fail.

05
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Install Drainage Mat

Install a drainage mat with molded dimples. The material used needs to create air gaps between the wall and itself so that moisture can travel to the drain structure. The drainage mat should be cut to the exact depth of the foundation. It can also help ease lateral pressure against the foundation.

06
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Complete the French Drain

Install the French drain or weeping tile. The pipe, 4” could be used, must be installed at the base of the footing weeping the water level below the basement floor. It is a good practice to install cleanouts, to provide easy to access for maintenance purposes.

Backfill with gravel and complete your French drain installation. Gravel should be 18″ from grade for earth areas, and 4″ from grade where cement will be poured.

07
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What to Avoid Doing

The following should be avoided when waterproofing a basement:

  • Do not use tar. Tar will become very brittle and will crack eventually.
  • Do not use plastic to waterproof your basement walls. The plastic-like material will peel, and moisture will make its way in.
  • Don't use limestone to backfill. Limestone will reduce drainage capabilities and could clog all drainage structures. Use gravel instead.