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Waterproofing Watchwords for HomeownersMarch 1st, 2012 by
Here are just a few terms that are useful to know when dealing with a professional waterproofing contractor.
Damp-proofing , like waterproofing, is applying materials and measures designed to resist water. Unlike waterproofing, damp-proofing is not made to resist water in the presence of strong hydrostatic pressure.
The materials used in the process are often asphalt- or tar-based, and they’re generally sprayed thinly and quickly over the structure. As the structure settles over time the coatings can flake or crack, leaving the structure vulnerable to water.
Damp-proofing is typical in new construction, particularly in states and municipalities where the building code does not specify a requirement to waterproof a structure. Builders generally choose damp-proofing as a cost-saving measure.
When water builds up in the soil—usually from heavy rains or snow melt—and it reaches a level where the amount of standing water is constant and the water has nowhere to flow, this creates pressure against a home’s foundation.
The occurrence is greatest in areas where the soil is composed more of solid rock and clay, as these soils do not allow for water to flow easily away from structures.
The weight of the water presses against foundation walls as the water seeks a path along which to flow, which can cause the walls to bow over time if the pressure is not relieved.
Water incursions are the result of hydrostatic pressure attempting to relieve itself along the least resistant path, which, unfortunately, is often into the basements and crawl spaces of a home through gaps or cracks in the foundation or footing.
A footing is a concrete slab used to support the weight of a structure’s foundation walls. Because footings are generally poured and cured at different times than the foundation walls they support, the crease where the footing meets the wall is often a prime spot for water under hydrostatic pressure to seep into a structure.
Drains are usually installed here to remove this water, but footing drain failure is the most common reason for leaks in foundations.
Contrary to what is commonly believed, a French drain is not named for the country of France but rather for Henry French, who popularized this type of drain in the 19th century.
A French drain consists of a trench that’s layered with rocks or gravel and contains a perforated pipe, which is buried in its basin among the rocks.
The drain serves to redirect both surface and groundwater away from structures, usually using gravity to help pipe the water to an area that is more suitable for dumping.
The gravel in a French drain is an especially important component, as it helps deter sediment from getting into the pipes and keeps them clear and flowing.
A strip drain is a type of footing drain often used in new construction. Typically consisting of a six- by one-inch PVC pipe with only a filter fabric surrounding it, a strip drain is installed at the base of the footing and then covered over with fill dirt.
Though widely used, some waterproofing professionals consider this type of drain to be inferior to other waterproofing methods, noting that its size does not displace a lot of water and it is likely to clog due to its placement, which is usually alongside the bottom of the footing, in direct contact with the soil.
However, there are newer strip drain products that are designed to rest on the top of the footing in the crease where the wall and footing meet.
While offering somewhat better performance, these drains are still not generally preferable to a pipe and stone system, particularly in areas where the soil is mostly fine clay.