Repairing and Sealing a Basement Cost

• Expect to pay $100 -$300 for do-it-yourself materials to patch any cracks in your basement walls or floor, then seal the interior basement walls or floor with a sealant. In extreme cases, if the cracks and leakage problems are extensive, you might also excavate outside a problem area in a wall, install exterior footer drains and backfill the excavated area. This could bump the total do-it-yourself cost up to $300 -$600 or more, especially if you rent a backhoe. A Long Island, NY homeowner spent $400 (including $300 to rent a backhoe) on a do-it-yourself project repairing three long cracks in the basement of his 3-bedroom home, sealing the interior walls and then excavating outside and sealing one exterior wall.
• Hiring a waterproofing or basement contractor to patch and seal your basement interior can run $1,000 -$2,000 or more depending on the size of the basement and the extent of the cracks and leaks. If the project also includes outside excavation and drainage as well as sealing exterior walls and covering them with a moisture barrier, the total costs might average $5,000 -$10,000, but can run $11,000 -$15,000 or more depending on regional prices and the size of the project.

• The basement walls or floors should first be cleaned of any dirt, grease and dust. If using a cement-based sealant, the surface needs to be wet thoroughly with a fine mist before applying the sealant. Depending on the type of sealant, usually two coats will be needed. When patching cement, the hole or crack should first be widened slightly and made at least half an inch deep. Better Homes & Gardens provides illustrated instructions for repairing basement leaks, including applying interior sealant and doing outside excavation and sealing.

• Extensive landscape replacement may be needed after outside excavation; the cost will vary considerably depending on the size of the area damaged by excavation and the type of replacement plantings chosen.

• Get estimates from several companies. Be sure you understand exactly which materials will be used and what work will be done -- and how the project will fix your specific basement water problems. The contract should include a written evaluation of the problem and how it will be fixed; start and completion dates; a guarantee or warranty; and a clause that there will be no additional work down without your consent, approval and signature (to avoid unwanted add-ons or unpleasant surprises with the final bill). Ask for and check references from satisfied customers, and look for any complaints on file with the Better Business Bureau. The BBB warns against waterproofing contractors who ask for large payments in advance or don't provide a written estimate.
• The National Association of Waterproofing and Structural Repair Contractors lists things to do before calling a contractor, a checklist for hiring a waterproofing contractor and referrals to its members in each state.

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