Frequently Asked Questions
Many problems can occur in a basement or foundation that was not designed to withstand the elements, its important to know the Facts and Forces behind a wet basement so these problems can be averted. This area was created to provide information on a wide variety of topics including:
|The force that a standing fluid, such as water, exerts. For example, standing water below grade exerts hydrostatic pressure on the foundation walls.|
|Capillary action allows water to defy gravity. Capillary vaction is the wicking of water into a porous material via adhesion (clinging to the concrete) and surface tension (clinging to itself). By clinging to the concrete’s surface, water can wick into the foundation through its pores. Water can wick into concrete, brick, wood, and any other porous materials. Water wicking through a foundation footing or slab is a good example of capillary action at work. The problem will show up as damp carpeting on a slab floor, or as dampness around the base of a foundation wall.|
Some products are designed to waterproof foundations, while other products only damp proof them. The American Society for Testing and Materials defines waterproofing as a treatment that prevents the passage of water under hydrostatic pressure.
Damp proofing, on the other hand, only resists the passage of water in the absence of hydrostatic pressure. Hydrostatic pressure is the force that is exerted on a foundation by the water that is in the ground that surrounds the foundation.
Less Expensive, Less Effective
There is strong evidence that damp proofing is insufficient in protecting basements against moisture penetration. 85% of builders questioned in a National Association of Home Builders survey said that at least some of the basements they have built leak.
The standard practice for damp proofing new basements is to apply one or two coats of unmodified asphalt (asphalt with no chemical additives) to the exterior side of the foundation walls from the footings to slightly above grade. This is less expensive than other methods, but also much less effective.
Asphalt emulsions are the easiest damp proofing substance to work with. Water-based emulsions can be applied to damp substrates, including green concrete; they aren’t flammable; they don’t emit noxious fumes; and they clean up with water. They also can be used for gluing extruded polystyrene foam insulation (XEPS) to foundation walls. On the downside, emulsions must be protected from rain and freezing until they have dried, which can take several days in cool weather. Backfilling too soon can cause an uncured emulsified coating to deteriorate
Cutback asphalts are solvent based and normally aren’t affected by rain or freezing. But most cannot be applied to green concrete or to wet substrates. Uncured, they’re toxic and combustible, and they dissolve foam insulation.
The trouble with unmodified asphalt in general is that it is a byproduct of the oil-refining process, and incremental improvements in refining technology gradually have eliminated asphalt’s elasticity. Today’s asphalts won’t span the cracks that invariably occur in the basement walls as concrete shrinks and foundations settle or move in response to various other conditions. Asphalts also tend to embrittle or emulsify with age, exacerbating the problem.
Rubber Damp Proofing
One alternative to asphalt is a Rubber Polymer. This type of damp proofing is much more flexible and better at spanning cracks than unmodified asphalt, but it degrades in sunlight and needs to be covered fast.
Polymer-modified cementitious coatings are also used for damp proofing. These cementitious coatings occupy the gray area of moisture-proofing. Typically brushed or troweled on, they bond tenaciously to cured substrates and, in some cases, even stand up to hydrostatic pressure. They also breathe, which helps prevent basement condensation; they require no protection board; and they look good where they’re exposed.
The trouble is, even the best polymer-modified cementitious coatings don’t reliably bridge shrinkage and settling cracks. Instead, they tend to crack where foundations do, admitting water where protection is needed most.
Waterproofing, Keeps All Moisture Out
If you elect to waterproof instead of damp proof, there are several factors to consider when choosing an appropriate material. Products can differ in everything from shelf life and compatibility with form-release agents to ease of application and cost. Some membranes require protection against backfill; others don’t. Also, some membranes can be installed by the average contractor, while others have to be installed by factory-certified technicians.
Liquid Applied Elastomeric Membranes
Sprayed-on liquids that cure to form elastic membranes are probably the most popular basement-waterproofing products on the market, and for good reason. Not only can they be applied quickly to concrete or masonry, but they also cure to form seamless, self-flashing membranes. These membranes conform to complex surfaces, such as curved walls or walls that have a lot of lines or pipes passing through, and they span cracks to 1/16 inches wide. Also, because the entire membrane bonds to substrates, leaks are confined to small areas that can be detected and repaired easily.
Dimple sheeting is relatively new in North America, but big in Europe as it is a low-cost waterproof membrane that doubles as a drainage mat. The sheeting is simply rolled over concrete, masonry, or wood foundations and tacked up with special washered nails. It can be installed over substrates in any condition and backfilled whenever you’re ready. The membrane not only repels water, but also forms air gaps against the basement wall that will channel to footing drains any groundwater that might get through the membrane. These air spaces also allow the escape of indoor water vapor that condenses on the outside of the foundation.