The foundation is a vulnerable place for water intrusion. Improper drainage around the foundation is a major cause of leaking foundations. When a drainage system is used in residential construction, it is usually a combination of a gravel drainage layer with a foundation drain, either drain tile or perforated PVC pipe. Months later, as drainage occurs, small soil particles can fill the drainage path, resulting in reduced drainage of ground water. Water pressure then builds up and eventually causes leakage through the foundation wall.
Engineered, prefabricated foundation drainage panels are designed to facilitate the movement of ground water to reduce the water pressure stress on the foundation waterproofing. The drainage panels provide an unobstructed path from surface grade to footing, allowing the footing drain to collect and remove water away from around the foundation. Some of these systems also provide thermal resistance and can reduce interior condensation.
Foundation drainage panel systems combine with waterproofing membranes to provide protection from ground water in areas where there is a high water table or hydrostatic pressure. The standard gravel drainage course and foundation drains with dampproofing on the foundation are applicable in areas with occasional or no groundwater.
The typical foundation drainage system consists of a waterproofing membrane at the foundation with a preformed path, whether a grid system or a solid, porous board, and a filter to keep the drain path clear of small particle build-up. The filter has been traditionally a course of specially-graded aggregates, ranging from crushed stone or gravel to coarse angular sand. Geotechnical fabrics, commonly called "filter fabrics", are now frequently used to allow the flow of water, while not allowing the small particles to pass through. These fabrics consume less space, are more reliable, and relatively easy to install.
The drainage path can be obtained by several different methods:
- Through a drainage board, solid board material, with a porous structure, allowing moisture and water to drain vertically down to the foundation drain. These board-type systems provide protection of the waterproof membrane and provide thermal insulation.
- Through an air space created by a dimpled plastic grid or "geogrid", a twisted plastic wire grid. Condensation can also be collected in this air space.
- The traditional gravel course, with filter fabric to the outside and protection board over the foundation waterproofing. Washed pea-gravel or screened crushed stone works well for this drainage course.
The panels with an air space quickly move the water to the drains, reducing hydrostatic pressure against the foundation. Most of these systems also provide protection to the dampproof or waterproof membrane.
Dimpled polyethylene sheets can be used in two ways:
- With the dimples toward the foundation wall. This provides an air space for condensation, using the back side as an impervious barrier. When properly sealed, the system resists ground water percolating through to the face of the foundation, thereby protecting it from the moisture.
- Some products have a filter fabric adhered to dimple side of the panel. In this case, the flat side of the panel is toward the foundation. The drainage path is created by the dimples and protected by the filter fabric.
Another method of providing a path with the filter fabric is the use of a "geogrid". A geogrid is a twisted-wire plastic mesh, often shaped into a diamond lath pattern, faced with filter fabric. These normally are rather thin, flat membranes offering effective drainage characteristics in a minimal space. EnkadrainTM employs a fused, entangled polymer-filament geomatrix, a plastic wire mesh, faced with filter fabric to provide the drainage layer.
American Wick Drain Corporation makes a sheet drain system connected to a strip drain at the bottom of the foundation wall. The strip drain can be connected to piping to lead the water away from the foundation. "Form-a-drain" by the Certainteed Corporation is a rectangular drainage conduit that also acts as a footing form, saving several installation steps.
Foamed plastic insulated panels may be used outside foundation walls to move water to drain tile or pipe at the bottom of the wall. As mentioned previously, these panels also provide thermal insulation. Panels may or may not be faced with a geotextile membrane. GeotechTM, for example, is an unfaced board of expanded polystyrene. It allows water to move between the bead structure of the material, and the polystyrene offers insulating value.
Other foam foundation panels are made from extruded polystyrene, grooved on the soil side, covered with filter fabric. The filter fabric allows the water into the grooves, which transfers it to the drain tile. The polystyrene insulation has a low permeability rating, and provides insulative value.
Some drainage panels are composed of rock (mineral) wool or fiberglass material oriented to provide vertical drainage to the foundation drain. No filter fabric is necessary with this material.
Dimpled polyethylene sheets can be used in two ways:
With the dimples toward the foundation wall. This provides an air space for condensation, using the back side as an impervious barrier. When properly sealed, the system resists ground water percolating through to the face of the foundation, thereby protecting it from the moisture.
Some products have a filter fabric adhered to dimple side of the panel. In this case, the flat side of the panel is toward the foundation. The drainage path is created by the dimples and protected by the filter fabric.
Another method of providing a path with the filter fabric is the use of a "geogrid". A geogrid is a twisted-wire plastic mesh, often shaped into a diamond lath pattern, faced with filter fabric. These normally are rather thin, flat membranes offering effective drainage characteristics in a minimal space. Enkadrain™ employs a fused, entangled polymer-filament geomatrix, a plastic wire mesh, faced with filter fabric to provide the drainage layer.
American Wick Drain Corporation makes a sheet drain system connected to a strip drain at the bottom of the foundation wall. The strip drain can be connected to piping to lead the water away from the foundation. "Form-a-drain" by the Certainteed Corporation is a rectangular drainage conduit that also acts as a footing form, saving several installation steps.
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Foundation drainage panels offer improvements over traditional granular fill that includes: lighter weight; greater dimensional stability; dependable and increased flow; full flow continuity; and protection against freeze-thaw and backfilling damage.
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Foundation drainage panels are readily available in several different configurations to accommodate local soil conditions. Some foundation drainage products may not be available for use with wood foundations or non-proprietary waterproofing systems. Warranties for the products generally range from one to five years. Longer warranties are typically available with insulated systems, but only available when used with waterproofing foundation coatings as opposed to lesser quality dampproofing.
Regardless of the type of drainage panel used, washed gravel is always necessary to properly bed and wrap drain tile. The dimples of non-geotextile-faced membranes can damage dampproofing or waterproofing applied to foundation walls. They do not offer an external pathway for ground water to reach the drainage tile/pipe as do other systems. Most drainage panels are effective to twelve feet below grade. Many of the products are only warranted by the manufacturer for use on masonry or concrete foundations.
Some fibrous drainage panels are only available when used together with a particular waterproofing membrane designed for concrete or masonry foundations, e.g. Tuff-n-Dri®.
Wholesale products range in cost from $.30 to $.45 per square foot, although geogrids may be slightly less.
Not Applicable
Most products have received building code approval. The National Evaluation Service (NES) has reviewed and accepted foundation drainage panel products, and has issued National Evaluation Reports (NER). On February 1, 2003, America's four building-product evaluation services officially combined their operations under the International Code Council. The four "legacy" evaluation services that came together to form ICC-ES were the National Evaluation Service, Inc.; BOCAI Evaluation Services; ICBO Evaluation Service, Inc.; and SBCCI Public Service Testing and Evaluation Services, Inc. Information on these NERs can be obtained by contacting ICC at their web site shown below (www.icc-es.org) or by clicking on any NER report number listed below under contacts.
Not Applicable
After the foundation wall has been constructed, dampproofing or waterproofing should be applied to the wall. The top of the drainage panel should be three to six inches below the top of the foundation wall, as recommended by the manufacturer. Full-size sheet products may be adhered or mechanically fastened at the top and draped down to the footing, or extended over the drainage tile/pipe, depending on the type of drainage panel used. Panels that are not large enough to extend full height should be started at the bottom of the foundation wall, working upward, with overlapping facings in shingle style.
Always follow manufacturer guidelines for care and installation to prevent voiding the warranty. These guidelines generally require filter fabric to be wrapped over and back down the backside of the panel about four to six inches prior to attachment to the foundation wall. The top of the panel is usually protected from being covered with soil. Care must be taken not to penetrate the waterproof membrane. Be sure that attachment of the drainage system does not affect the waterproofing membrane, either in attachment or by pulling and tearing the membrane during backfilling and soil settling.
It is important to understand how the material works and apply it to the wall correctly, with the correct side out, so that it can fulfill its purpose. After installation, the panel and drainage tile/pipe should be adequately tested to ensure that water flows into and out of the system.
0-30 years dependent on manufacturer
Foundation drainage panels offer improvements over traditional granular fill that includes: lighter weight; greater dimensional stability; dependable and increased flow; full flow continuity; and protection against freeze-thaw and backfilling damage.
Insulated systems offer the increased benefit of energy savings (up to R-5 per inch), improved interior comfort and reduced likelihood of interior mold and mildew growth from condensation on cold basement walls. Should insect infestation occur in fibrous panels, they may be successfully treated with insecticides.
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