What does ENERGY.GOV tell you about the need to control moisture in your home? CLICK HERE and see!
In construction, a building or structure is waterproofed with the use of membranes and coatings to protect contents, and structural integrity.
In building construction, waterproofing is a fundamental aspect of creating a building envelope, which is a controlled environment. The foundations must be water-resistant and sometimes waterproof. Many types of waterproof membrane systems are available, including felt paper or tar, bituminous waterproofing, liquid sealant and more.
Copyright 2019. EcoMaster LLC. All rights reserved.
Protection Boards are used to shield waterproofing membranes from construction damage, damage from backfill materials in service, and ultraviolet radiation. The most commonly used protection board is a semi-flexible sheet containing an asphalt core placed between asphalt impregnated glass fiber mats. The material may have polyethylene film on one side and a glass mat surface on the other side. For some membrane applications such as hot-applied bitumen systems, the protection board is embedded into the wet membrane forming an integral part of the waterproofing membrane. Asphaltic protection boards are available in 1/16, 1/8 and 1/4 inch in thickness. Other materials sometimes used as protection layers are extruded polystyrene rigid board insulation or prefabricated synthetic drainage layers.
In general, using prefabricated composite drainage board directly against certain waterproofing membranes as a protection layer is not recommended. Although the composite board may have a polyethylene sheet on the membrane-side, this sheet is often cut, damaged, or missing. If installed, soil pressures can cause the "dimples" in the drainage core to displace or damage the waterproofing membrane. Additionally, the composite cores have sharp corners that can cut the waterproofing membrane during installation or backfill operations. Therefore, a protection layer is recommended between the waterproofing membrane and the drainage layer.
In buildings using earth sheltering, a potential problem is too much humidity, so waterproofing is critical. Water seepage can lead to mold growth, causing significant damage and air quality issues. Properly waterproofing foundation walls is required to prevent deterioration and seepage.
Waterproofing membrane systems are available as either post-applied or pre-applied products for use in either positive-side, negative-side, or blind-side applications. Positive-side waterproofing systems are post-applied to the surface of the element that is directly exposed to moisture, typically the exterior side of the foundation wall. Negative-side waterproofing systems are post-applied to the surface of the element opposite the surface exposed to moisture, typically the interior of the foundation wall. Blind-side waterproofing systems are pre-applied to the area where the concrete element will be placed that is directly exposed to moisture. Positive-side systems are available in numerous materials and forms. Negative systems are generally limited to cementitious systems. Blind-side systems are typically either a waterproofing sheet or an impermeable clay-based material.
Waterproofing membranes can be categorized into four (4) types:
Fluid-Applied Systems—These systems include urethanes, rubbers, plastics and modified asphalts. Fluid-applied membranes are applied in liquid form and cure to form one monolithic seamless membrane. For foundation wall applications, typical cold applied fluid applied systems are approximately 60 mils in thickness. Some systems include reinforcing mesh embedded into the liquid. Hot applied, rubberized asphalt systems can be 125 mils to 180 mils thick, plus embedded 60 mil neoprene sheets.
Sheet-Membrane Systems—Sheet membranes used in foundation wall applications include thermoplastics, vulcanized rubbers, and rubberized asphalts. The thickness of these systems varies from 20 to 120 mils. If heat-welded seaming is employed and loose-hung membranes are tough and protected from damage by protection board, they may be effective waterproofing materials, but if a leak occurs, the leak will be difficult to locate and correct due to the loose application of the waterproofing layer in those cases. It is always better to have a continuously bonded and adhered waterproofing layer to reduce the potential for lateral moisture migration beneath the membrane.
Bentonite Clays—These systems include composite sodium bentonite systems with HDPE liners and geotextile fabrics, which are more common and more effective than the traditional systems. Bentonite clays act as waterproofing by swelling when exposed to moisture thus becoming impervious to water. This swelling can be 10 to 15 percent of the thickness of the base material. Bentonite is, therefore, most effective when properly confined so the product can swell to fill voids and so that it cannot be washed away. If Bentonite clay is unconfined, it can shrink upon drying, creating gaps that undermine waterproofing characteristics. Clay panels and geotextile sheets are popular for use in blind-side waterproofing applications such as on retaining earth systems and elevator and sump pits.
Cementitious Systems—These systems contain Portland cement and sand combined with an active waterproofing agent. These systems include metallic (metal oxide), crystalline, chemical additive, and acrylic modified systems. The latter two should not be used as waterproofing except for the most non-critical conditions. The first two systems can be applied as negative-side or positive-side waterproofing. Even these systems should only be considered for use as a secondary (back-up) waterproofing to a positive-side waterproofing system, unless they are used with special details provided by a waterproofing expert which are beyond the scope of what are usually provided by system manufacturers.
Waterproofing should be applied a minimum of 12" above finished grade, and then applied to a point 12" below the top surface of the interior slab on grade. Typically, the waterproofing is wrapped over a masonry brick shelf, or up behind the finish exterior materials at grade so that it may be terminated and shingle lapped by the weather barrier. When it is wrapped over masonry ledges, care must be taken to coordinate with masonry ties and thru-wall flashings. Where grade slopes down along an exterior wall, the waterproofing will step down incrementally so that it continues to protect the below grade, occupied space.
If the exterior wall materials will not protect the waterproofing at grade, base flashings should be used to protect the waterproofing from ultraviolet (UV) radiation exposure. These flashings are usually stainless steel to resist corrosion in contact with grade soils and moisture.
In some situations, it may not be possible to apply waterproofing directly and entirely to the foundation walls, and it may be necessary to fasten a "lens" membrane to the foundation wall to catch runoff and redirect it away from the foundation. It is recommended that a 60 mil PVC membrane or polyolefin membrane be used, set on a concave sand bed and fastened to the foundation wall with a stainless steel termination bar with standard waterproofing applied to the wall above that point. The lens membrane should slope away from the building and collect and redirect the runoff to a drain tile or sump away from the foundation.
The concrete in foundations needs to be damp-proofed or waterproofed with a liquid coating, basement waterproofing membrane (even under the concrete slab floor where polyethylene sheeting is commonly used), or an additive to the concrete.