How to Seal Basement Floors & Foundation Walls Against Water & Moisture
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Basement sealers to control moisture & water entry: this article discusses options for sealing basement or crawl space floors and walls, or other building foundation walls to stop water entry and to reduce interior moisture and mold risks. The photograph at page top shows a very wet basement foundation wall built of concrete block. The stain pattern extends high on the basement walls, down the full wall, onto the basement floor. Correcting this particular water entry problem should begin outside with roof drainage and surface runoff. This article discusses foundation wall and floor slab sealant options. .
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Basement Waterproofing Using Sealers for Concrete Floors & Masonry Foundation Walls
Aaron Kuertz, Applied Technologies, Inc.
Details about water barrier coverings for foundations are at WATER BARRIERS, EXTERIOR BUILDING and FOUNDATION WATERPROOFING and also GEOTEXTILES & DRAINAGE MATS. See WET BASEMENT PREVENTION for a description of the critical steps to prevent basement water entry and foundation leaks. Also see BASEMENT LEAKS, INSPECT FOR for articles on diagnosing building water entry, and see CRAWL SPACE Dryout Procedures.
Basement Concrete and Concrete Block Sealers for Basement Waterproofing
Basements are below grade and surrounded by soil. This soil absorbs water during rains and then releases it. The water can migrate through a block basement and even through solid concrete such as in walls and floors by capillary action.
This water that enters the basement can cause problems ranging from peeling paint to mold and mildew growth. Also, naturally occurring gasses that are released from soils can be transmitted into the basement. The interior basement air quality is lessened unless the walls and floors are sealed.
It is possible to seal the concrete or concrete blocks used in basement walls and floors and stop water and gas migration into a basement. In fact, it can be done from the interior of a home. Old homes and new homes alike can be sealed. |
Using Exterior Foundation Coatings to Repair Foundation Wall Cracks & Leaks
As Carson Dunlop Associates' sketch shows, foundation crack leaks can be repaired from outside the foundation wall using a combination of asphalt-mopped d & roofing and a waterproof bituminous membrane that is then adhered to the wall surface.
Sodium Silicate Sealers for Floor & Foundation Wall Waterproofing
Sodium silicate is used in a water-based mixture to seal the basement walls and floors.
The sodium silicate penetrates up to 4” into the substrate.
After penetrating the sodium silicate reacts with the free lime content of the concrete or masonry . Concrete, concrete block and masonry has lime as a natural component in their composition.
This reaction between the sodium silicate and free lime produces a solid crystalline structure that fills the microscopic cracks and pores of the substrate. This hardens and densifies the concrete and masonry so that water vapor and gasses cannot migrate through by capillary action. Also, gasses are retarded from entering a basement. After curing, the substrate looks the same as if it were not sealed. There is no surface film or sheen to it.
Benefits of Sodium Silicate for Building Waterproofing
By sealing the basement walls and floors with sodium silicate water vapor will be stopped from entering into a basement. The basement will be dryer than before. This greatly improves the interior air quality of a home by retarding the growth of mold and mildew.
Since the surface of the walls and floors are hardened, they will have less dusting and chalking. Gas transmission will be reduced as well, further improving air quality.
Many people like to paint the floors and walls of their basements. If paint is applied to unsealed walls and floors, it is possible for the water vapor to get trapped under the paint. After a period of time the water vapor can break the bond between the paint and the substrate. This causes the paint to blister and peel.
After application of a sodium silicate the walls and floors can be painted without fear of the paint peeling and flaking. Also, adhesives for tiles or other floor coverings can be used.
Application of Sodium Silicate for Basement or Crawl Space Waterproofing
Sodium silicate is applied to bare concrete, concrete block or masonry. Anything that would prevent the sodium silicate from being absorbed must be removed. No grease, dirt, soil, adhesives, oil, sealer or paint can be on the surface to be sealed prior to application.
Application is done simply by using a garden sprayer, roller or brush. First dampen the surface with water using a mop or brush. Apply in areas 10’ x 10’ in several light coats. Apply each coat after 10-20 minutes. Concrete takes 2-3 coats, concrete block and masonry 3-4 coats. Do not over apply the sodium silicate since if all of the product is not absorbed it may leave a white residue. Wipe up any excess product.
For several days after application loose dirt will be pushed out of the substrate. This is normal and can be swept off.
A Few Caveats about Any Foundation Sealer or Weather Barrier Product - DF OPINION
Watch out: any surface coating, even a penetrating wall sealer such as discussed here, can fail if exposed to continued or chronic water and water pressure through the foundation wall.
The pressure from water, frost, or more significantly, the formation of efflorescent salts (see EFFLORESCENCE, Salts & White / Brown Deposits) can exert tremendous pressure, sufficient to separate a paint or other coating from a masonry foundation surface. Efflorescence has been cited in several paint failure studies where these forces were explored.
Some factors that affect the durability and thus success of any foundation coating or waterproofing coating include:
- The cleanliness of the surface to which the coating is applied
- Application of the sealer according to the manufacturer's instructions, including specifications of pre-cleaning, thickness, temperature, humidity at time of application
- The degree of water intrusion or water presence on the exterior of the foundation wall
- Climate, freezing temperatures
- Chemistry of both the masonry wall and the water, affecting the formation of efflorescence
- Chemistry, composition, and in some cases fiber reinforcement of the coating
Watch out: sodium silicate is an alkaline substance that can cause burns, eye, and skin damage. Quoting from a MSDS:
Causes moderate skin irritation. Spray mist
causes irritation to respiratory tract. Due to high pH of
product, release into surface water is harmful to aquatic life. ... Causes severe irritation to the eyes. ... Causes moderate irritation to the skin. ... Spray mist irritating to respiratory tract. ... May cause irritation to mouth, esophagus, and stomach. ... No known chronic hazards. Not listed by NTP, IARC or OSHA
as a carcinogen. ... Dries to form glass film which can easily cut skin. Spilled
material is very slippery. Can etch glass if not promptly
removed.
...
Human experience indicates that skin irritation occurs, particularly,
when sodium silicates get on clothes at the collar, cuffs or other areas
where contact and abrasion may occur.
The acute oral toxicity of this product has not been tested. - MSDS for Sodium Silicate from PQ Corporation
Also see this MSDS for Krystol Hydrostop WB [copy on file as /exterior/Krystol-hydrostop-wb.pdf ] - WB from Kryton Corporation.
Thanks to reader Stan Rosenbaum for alerting us to the need for care when working with sodium silicate.
Weather Barrier Coatings, Mastics, Sealants, Adhesives used on buildings, Building Sheathing & Building Foundation Coatings
AkroGuard, Omega Products, International, 1681 California Ave, Corona, CA 92881, Tel: 800-600-6634, 951-737-7447,
Fax: 951-520-2594, Quoting from the company's product description:
AkroGuard is a field applied, non-cementitious, [acrylic] flexible coating that when used with AkroFill creates a water-resistive barrier over approved substrates.
Basic Uses:
AkroGuard is designed for use as a water-resistive barrier and air barrier over approved substrates and with the AkroFlex EIF Systems. Complies with ICC-ES Acceptance Criteria for Water-resistive Coatings (AC212).
AkroGuard may be applied to the following substrates:
- Gypsum sheathing
- Fiber-faced gypsum sheathing
- Wood-based sheathing
- CMU/Poured-in-place and/or tilt-up concrete/masonry
- Cement board
Thanks to reader J. Campbell for pointing out this product, March 2010.
Krystol Hydrostop, Kryton Corporation, "Crystalline Waterproofing" masonry sealer. MSDS for Krystol Hydrostop WB [copy on file as /exterior/Krystol-hydrostop-wb.pdf ] - WB from Kryton Corporation. Masonry sealer.
- Krystol T1 and T2 waterproofing system is brush-applied onto concrete surfaces to become an integral part of the concrete. It contains Kryton's renowned waterproofing chemicals and is durable and self-sealing.
Vi-Cryl CP-10 (Trowel Grade) & Vi-Cryl CP-11 (Spray/Brush) Weather Barrier Coatings, Childers Corporation. We discuss the use of this coating at INSULATION LOCATION for BASEMENT WALLS. Quoting from the company's product literature [copy on file as /exterior/Vi_Cryl_cp-10-11.pdf ] - ,
VI-CRYL CP-10/11 weather barrier coating is unsurpassed for the
mechanical protection and weatherproofing of thermal insulations both
outdoors and indoors, in hot, cold, and dual-temperature service.
However, since it is a ‘breathing’ coating (vapors under pressure will
pass through it) it should only be used over insulations in lowtemperature,
or dual-temperature service when the insulations
themselves are vapor barriers.
VI-CRYL CP-10/11 has also found use
throughout the thermal insulation industry as a coating used over closed
cell polyethylene and polyurethane foam insulations. Industry
experience has demonstrated that all weather barrier coatings may
blister when applied over polystyrene board. This effect may be limited
by the use of white colored coatings.
VI-CRYL CP-10/11 weather barrier
coating in its Metallic Gray color is the ideal companion product to
Aluminum and Stainless Steel Jacketing. VI-CRYL CP-10/11 gives
superior mechanical and chemical protection to any irregular shape or
surface where the application of Childers Metal Jacketing Systems is impractical.
Also see INSULATION LOCATION for BASEMENT WALLS,
see WET BASEMENT PREVENTION for our complete list of basement dry-out or water entry prevention methods.
Frequently Asked Questions (FAQs) About paints, sealants, crack fillers used to seal leaky basements & crawl spaces
Question:
I have a leak in my basement what do I use to seal leak thank you. - R.Y. 12/12/2012
Reply:
Before sealing a basement leak, it's important to identify the water source - else the leak will continue or will reappear nearby. Find and fix the cause.
With that step taken, depending on the leak point and building surfaces involved (which you haven't yet described) we can recommend some solutions. The choice of best sealant or coating depends in part on what kind of surface is to be sealed and second the nature of the moisture, dampness, or water entry trouble.
See
for complete guidance on finding, fixing, and preventing basement water entry. You might also want to take a look at
- Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Aaron Kuertz is with Applied Technologies, Fairfield, OH 45018, 877-APPLY-IT (277-5948). (513) 939-3767. Mr Kuertz has been in the waterproofing industry since 1998. Applied Technologies is a manufacturer of waterproofing products used by both professional contractors and homeowners alike. For more information on Hydra Block™ water-based concrete and masonry penetrating sealer used for concrete and concrete block basement sealing, see Applied Technologies at www.appliedtechnologies.com
- Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
- John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- Kryton Corporation, 1645 Kent Ave., Vancouver BC Canada VSP 2S8 - 604-324-8280 email: info@kryton.com
- PQ Corporation, P.O. Box 840. Valley Forge, PA 19482-0840, is a producer of sodium silicate. Quoting:
PQ Corporation is a leading producer of silicate, zeolite, and other performance materials serving the detergent, pulp and paper, chemical, petroleum, catalyst, water treatment, construction, and beverage markets. It is a global enterprise, operating in 19 countries on five continents, and along with its chemical businesses, includes Potters Industries, a wholly owned subsidiary, which is a leading producer of engineered glass materials serving the highway safety, polymer additive, metal finishing, and conductive particle markets.
- Thanks to reader Stan Rosenbaum for discussing sodium silicate hazards - June 2010
- Childers Corporation, Specialty Construction Brands, Inc., producer of Vi-Cryl [copy on file as /exterior/Vi_Cryl_cp-10-11.pdf ] - water based vinyl-acrylic mastic coating for thermal insulation, 315 South Hicks Rd., Palatine IL 60067 800-231-9541 or 800-338-2975
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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