Acrylic Modified Waterproofing Systems

Acrylic modified cementitious systems add acrylic emulsions to a basic cement-and-sand mixture. These acrylics add waterproofing characteristics and properties to in-place materials. Acrylic systems are applied in two trowel applications, with a reinforcing mesh added into the first layer immediately upon application. This mesh adds some crack-bridging capabilities to acrylic installations. However, since the systems bond tenaciously to concrete or masonry substrates, movement capability is limited.

Acrylic cementitious systems are applicable with both positive and negative installations.
Concrete substrates can be damp, but must be cured for acrylic materials to bond properly. Alkaline substrates can deter performance of acrylic-modified cementitious systems. Acrylic-modified materials are applied in a total thickness of approximately  1 8 in.

Reinforcing mesh eliminates the need for protective covering of the systems on floor areas in minimal or light-traffic interior areas.

The properties of all types of cementitious systems are summarized in Table 2.4.

Chemical Additive Waterproofing Systems

Chemical cementitious systems are a mixture of sand, cement, and proprietary chemicals (inorganic or organic), which when applied to masonry or concrete substrates provide a watertight substrate by chemical action. Proprietary chemicals are unique to each manufacturer, but typically include silicate and siloxane derivatives in combination with other chemicals. While the chemicals do not penetrate the substrate like the other cementitious systems, chemical systems also effectively become an integral part of the substrate after application.

Chemical cementitious systems, approximately 1 16-in thick, are thinner applications than other cementitious products. As with all cementitious systems, concrete or masonry substrates need not be dry for application. Chemical systems do not require curing, but capillary systems do.

Capillary/crystalline Waterproofing Systems.

Capillary/crystalline systems are mixtures of cement and sand in combination with proprietary chemical derivatives in dry or liquid form. The systems are applied in trowel, brush, or spray applications. Unlike other cementitious systems however, capillary have the additional advantage of an application using only the dry mix product that is broadcast directly over concrete that has not yet reached final set and cure. This is referred to as the “dry-shake” method, commonly used on slab components as a vapor barrier, as additional protection with below-grade slab waterproofing systems, or as a stand-alone waterproofing system. A typical dry-shake application is shown in Fig. 2.36.

A capillary/crystalline system not only waterproofs, as a system itself; the chemical additives are able to penetrate into the concrete wall or slab and react with the calcium hydroxide and available capillary water present to form crystalline structures within the concrete itself. These crystalline structures block transmission of water through the sub- strate, adding additional water repellency to the envelope components.

FIGURE 2.36 Dry-shake application of crystalline cementitious waterproofing.

The chemical process begins immediately upon application of the waterproofing system but can take as many as 30 days to fully reach maximum repellency. Once fully cured, capillary/crystalline systems have been tested to withstand hydrostatic pressures as great as 400 ft of water head. These systems have other advantages compared to other cementitious systems, including the following:

● No need for a protection layer.
● Some products have stated capability to seal hairline cracks that occur after installation.
● Most are not harmed in the presence of chemicals and acids, making their application ideal for storage tanks, sewage treatment facilities, and similar structures.
● Penetrate and react with the concrete substrate to form additional “belt and suspenders” protection.

Curing installed systems is critical for adequate crystalline growth. The curing should continue 24–48 hours after installation. Concrete or masonry substrates must be wet to apply these systems, which may be installed over uncured concrete.

In exposed interior applications, coating installation should be protected by plastic, dry- wall, or paneling applied over furring strips. Floor surfaces are protected by concrete overlays, carpet, or tile finishes.

Metallic Waterproofing Systems.

Metallic materials contain a mixture of sand and cement with finely graded iron aggregate or filings. When mixed with water to form a slurry for application, the water acts as an agent permitting the iron filings to oxidize. These materials expand due to this oxidizing, which then effectively seals a substrate and prohibits further transmission of water through the material. This system is one of the oldest methods used for waterproofing (first patented in 1906) and remains today an effective waterproofing system. (See Fig. 2.35.) Metallic systems are applied in two or three coats, with the final coat a sand and cement mixture providing protection over base coat waterproofing where exposed. This final coat seals the metallic coats and prevents leaching or oxidization through paints or finishes applied over waterproofed areas. To prevent excessive wear, concrete toppings are installed over horizontal exposed surfaces subject to pedestrian or vehicular traffic.

FIGURE 2.35 Negative application of cementitious water-
proofing.

If drywall or paneling is installed over the waterproofing, furring strips are first applied by gluing them directly to the cementitious system. This eliminates nailing the boards through the cementitious membrane. Carpet perimeter tracks should be applied in the same manner to prevent damage.

CEMENTITIOUS WATERPROOFING SYSTEMS.

Cementitious waterproofing systems contain a base of Portland cement, with or without sand, and an active waterproofing agent. There are four types of cementitious systems: metallic, capillary system, chemical additive systems, and acrylic modified systems.

Cementitious systems are effective in both positive and negative applications, as well as in remedial applications. These systems are brushed or troweled to concrete or masonry surfaces and become an integral part of a substrate.

Cementitious systems are excellent materials for use with civil and infrastructure projects, both above and below-grade, using both positive and negative applications. These projects generally consist of large concrete components that make the same generic composition cementitious systems relatively easy to specify and install without compatibility problems. Among the types of structures cementitious systems are used for:

● Tunnels
● Underground vaults
● Water reservoirs
● Water and sewage treatment facilities
● Elevator and escalator pits
● Below-grade concrete structures
● Swimming pools
● Cooling tower basins

In new construction, where costs and scheduling are critical, these systems are particularly effective. They do not require a completely dry substrate, and concrete does not need to be fully cured before application. This eliminates well pointing and the need for water control during construction. These systems apply to both walls and floors at one time, thereby eliminating staging of waterproofing operations. No subslabs are required for horizontal applications in new construction preventative waterproofing installations.

Finally, in cases such as elevator pits, the waterproofing is completed almost any time during construction as best fits scheduling.

All cementitious systems are similar in application and performance but repel water differently by the proprietary additives of a manufacturer’s formulations. Cementitious systems have several mutual advantages, including seamless application after which no protection board installation is necessary.

All cementitious materials lack crack bridging or elastomeric properties but are successfully applied to below-grade areas that do not experience thermal movement. However, below-grade areas are subject to freeze-thaw cycling and structural settlement. If these cause movement or cracking, a cementitious system will crack, allowing water infiltration.

⇒ Metallic systems   Metallic materials contain a mixture of sand and cement with finely graded iron aggregate or filings. When mixed with water to form a slurry for application, the water acts as an agent permitting the iron filings to oxidize. These materials expand...

⇒ Capillary/crystalline systems   Capillary/crystalline systems are mixtures of cement and sand in combination with proprietary chemical derivatives in dry or liquid form. The systems are applied in trowel, brush, or spray applications. Unlike other cementitious systems however...

⇒Chemical additive systems  Chemical cementitious systems are a mixture of sand, cement, and proprietary chemicals (inorganic or organic), which when applied to masonry or concrete substrates provide a watertight substrate by chemical action. Proprietary chemicals...

⇒ Acrylic modified systems   Acrylic modified cementitious systems add acrylic emulsions to a basic cement-and-sand mixture. These acrylics add waterproofing characteristics and properties to in-place materials. Acrylic systems are applied in two trowel applications, with a reinforcing...

WATERPROOFING: POSITIVE AND NEGATIVE SYSTEMS.

In new and remedial installations, there are both negative side and positive side below-grade systems. Positive-side waterproofing applies to sides with direct exposure to water or a hydrostatic head of water. Negative-side waterproofing applies to the opposite or interior side from which water occurs. Examples are shown in Fig. 2.34.

FIGURE 2.34 Below-grade positive and negative waterproofing details.

Although both systems have distinct characteristics, as summarized in Table 2.3, the majority of available products are positive-type systems. Negative systems are limited to cementitious-based materials, which are frequently used for remedial applications. Some materials apply to negative sides of a structure for remedial applications but function as positive-side waterproofing. These materials include chemical grouts, epoxy grouts, and pressure grouts. Admixtures (material added or mixed into mortars, plaster, stucco, and concrete) have both positive and negative features but are not as effective as surface-applied systems.

TABLE 2.3 Comparison of Positive and Negative Waterproofing Systems*

The principal advantage of a negative system is also its principal disadvantage. It allows water to enter a concrete substrate, promoting both active curing and the corrosion and deterioration of reinforcing steel if chlorides are present. Positive-side waterproofing produces an opposite result—no curing of concrete, but protection of reinforcing steel and of the substrate itself.

Positive and negative below-grade systems include

● Cementitious systems
● Fluid-applied membranes
● Sheet-membrane systems
● Hydros clay
● Vapor barriers

PREVENT CAPILLARY ACTION - CONSTRUCTION DETAILS.

Construction details must be included to prevent natural capillary action of soils beneath foundations or below-grade floors. Capillary action is upward movement of water and vapor through voids in soil from wet lower areas to drier high areas. Capillary action is dependent upon the soil type present. Clay soils promote the most capillary action, allowing more than 10 ft of vertical capillary action. Loose coarse gravel prevents capillary action, with this type of soil promoting virtually no upward movement.

Capillary action begins by liquid water saturating lower areas adjacent to the water source. This transgresses to a mixture of liquid and vapor above the saturation layer.

Finally, only vapor exists in upper soil areas. This vapor is as damaging as water to interior building areas. Soil capillary action can add as much as 12 gal of water per day per 1000 sf of slab-on-grade area if insufficient waterproofing protection is not provided.

Microscopic capillaries and pores that naturally occur in concrete substrates create the ability for the concrete to allow water and moisture to move readily through below-grade walls and floors. This process is particularly sustainable when the interior space of the structure has lower humidity than the 100% humidity of the adjacent water-saturated soil and when the occupied space is warmer than the soil. These conditions present ideal circumstances for water to be actually drawn into the occupied space if not protected with waterproofing materials or at minimum vapor barriers where appropriate.

Water vapor penetrates pores of concrete floors, condensing into water once it reaches adjacent air-conditioned space. This condensation causes delamination of finished floor surfaces, mildew, and staining.

Therefore, it is necessary to prevent or limit capillary action, even when using waterproof membranes beneath slabs. Excavating sufficiently below finished floor elevation and installing a bed of capillary-resistant soil provides drainage of water beneath slabs on grade.

This combination of foundation drainage and soil composition directs water away from a structure and is necessary for any waterproofing and envelope installation. Refer again to Fig. 2.1 for recommended controls for proper surface and groundwater.

FIGURE 2.1 Below-grade drainage detailing.

HYDROPHILIC/BENTONITE/ASPHALT RUBBER - WATERPROOFING.

These systems are all installed after the first concrete placement has occurred, with the materials attached directly to the first half by a variety of methods. The waterstop is supplied in rolls in lengths of several hundred feet and the material is adhered to the substrates by a variety of methods as recommended by the manufacturer.

Typically, the concrete does not need to be cured completely, as this would interfere with the placement schedule of the concrete. Substrate preparation is usually minimal, ensuring that there are no form release agents, fins, or other protrusions that can damage or puncture the waterstop during installation. Attachment is completed by a variety of methods, some as simple as nailing the strip to the concrete to hold it in place temporarily until the second half of concrete placement occurs.

It is imperative that the hydrophilic and bentonite materials are not left exposed to rain-fall before concrete is placed. If this occurs, the material will swell and lose all its capability to seal the joint after concrete placement. The photographs in Fig. 2.33 show a typical waterstop installation using a swelling material that is adhered to the substrate with sealant.

FIGURE 2.33 Installation of swell-type waterstop.

WATERSTOP INSTALLATION - WATERPROOFING.

PVC/Neoprene Rubber/Thermoplastic Rubber
Waterstops of this type are placed in the concrete formwork and tied or secured to firmly position the material during concrete placement. It is imperative that the waterstop is never allowed to fold over during concrete placement. Figure 2.23 shows some typical methods to secure the waterstop prior to the first concrete placement. Figure 2.24 details the method for installing waterstop using a keyed joint.

FIGURE 2.23 Securing of PVC waterstop for first concrete placement.

FIGURE 2.24 Formwork with keyway joint sys-
tem. Note the bulb is centered directly in midpoint
of the joint to ensure proper functioning as an
expansion joint.

To secure the flange in place for both concrete placements, the waterstop is generally secured using wires tied to the reinforcing steel every 12 in. The wire should be tied through the first or second ribs of the waterstop flange, never going beyond the second flange as shown in Fig. 2.25.

FIGURE 2.25 Securing PVC waterstop for second con-
crete placement.

Note that in each of these details the center bulb is directly in the midpoint of the joint. This is to ensure that the waterstop acts properly as an expansion joint during anystructural movement.

The bulb must never be placed completely in one side of the placement or it will lose all its capability to act as an expansion material. Nails or any other construction debris should not be allowed to puncture the waterstop bulb or any part of the flange near the bulb.

When using waterstops at construction joints, material with bulb ends makes securing to reinforcing steel easier by using wire rings that pass through the bulb but not the flange. Figure 2.26 details the steps using this system for both halves of the concrete placement.

FIGURE 2.26 Placement procedures for end bulb waterstop.

Placing PVC and rubber waterstops in the field usually requires some welding to joint ends of rolls or making necessary changes in plane. Waterstop should never be installed by merely lapping the ends together. The material must be heat-welded to fuse the ends together by using manufacturer-supplied splicing irons that melt the ends that are then held together until they cool, forming one continuous piece. Refer to Fig. 2.27 for a field weld application.

FIGURE 2.27 Field welding operation of PVC waterstop.

Testing of failed joints usually reveals that failures were either the cause of improperly positioned material, Fig. 2.28, (folded over during concrete placement) or where directional changes occurred in structure that the waterstop did not conform to. Whenever heat welding is used, the material is adversely affected at this point and its properties are not equal to the original material. Therefore it is recommended that whenever major directional changes are designed into a structure, the contractor should secure prefabricated fittings.

FIGURE 2.28 Improperly positioned, placed, and secured waterstop.

Waterstop manufacturers will usually provide a variety of premolded splice pieces for directional changes,
as shown in Fig. 2.29. Also, most manufacturers will offer to custom-make the required splices to ensure the successful applications with their material.

FIGURE 2.29 Typical manufactured PVC waterstop splices and transition pieces.

At all penetrations in below-grade slabs or walls, waterstop should also be installed continuously around the penetration to protect against water penetration. Figure 2.30 details the use of waterstop installed continuously around a structural steel column that penetrates the concrete slab over the foundation.

FIGURE 2.30 Waterstop application around structural steel column foundation supports.

Photographs in Figs. 2.31 and 2.32 show how complicated waterstop installations can become. Such detailing necessitates the use of premanufactured weld splices to ensure watertight applications. These photographs also emphasize how important proactive job-site quality-control procedures are, to verify that the PVC waterstop is installed and maintains proper positioning during concrete placement.

FIGURE 2.31 Placement of spliced PVC joint in form-
work.

FIGURE 2.32 Field quality-control procedures ensure successful
installation of waterstop.

WATERSTOPS - WATERPROOFING.

Whenever a construction joint occurs in a below-grade concrete structure, a waterstop should be installed in the joint to prevent the transmission of water through the joint.

Construction joints, also referred to as “cold-joints,” occur when one section of concrete is placed and cured or partially cured before the adjacent concrete placement occurs. This occurs frequently in concrete structures at locations including

● Transitions between horizontal and vertical components
● When formwork is insufficient to finish the structure in one placement, such as long lengths of wall area
● Where design elements require a change in form design
● When concrete placement is stopped, for schedule reasons or end of workday

In most of these cases a joint is not actually formed; the cold or construction joint reference refers to the area of concrete structures where two different concrete placements have occurred (properties of concrete preventing it from forming an excellent bond to itself and the previously placed concrete). In addition, control joints are added to a poured-in-place concrete structure to control cracking that occurs from shrinkage in large placements. Control joints are typically recommended for installation at no more than 30 ft apart. The joints are typically the weakest points of the concrete structural components, but not subject to movement other than structural settlement.

Below-grade conditions present conditions that make it very likely that water, which is present under hydrostatic pressure, will infiltrate through these construction joints. To prevent this from occurring, waterstops are commonly specified for installation at every construction joint on concrete work below-grade. The capability of waterstops to prevent infiltration at these weak points in the structure is critical to successful waterproofing of below-grade structures, so their importance should never be underestimated.

Waterstops are used for waterproofing protection on a variety of below-grade concrete structures including

● Water treatment facilities
● Sewage treatment structures
● Water reservoirs
● Locks and dams
● Basement wall and floors
● Parking structures
● Tunnels
● Marine structures

Waterstops are premanufactured joint fillers of numerous types, sizes, and shapes.
Waterstops are available in a variety of compositions including

● Polyvinyl chloride (PVC)
● Neoprene rubber
● Thermoplastic rubber
● Hydrophilic (modified chlorophene)
● Bentonite clay
● Asphalt plastic

The first three, PVC and rubber types, are manufactured exclusively for use in poured-in-placed concrete structural elements. The remaining three, while mainly used for concrete installations, can be used with other building materials such as concrete block and are also excellent where installations involve metal protrusions in or adjacent to the construction joint. Manufacturers also make waterstops that are resistant to chemicals and adverse groundwater conditions. A summary of the properties of the various type water-stop is shown in Table 2.1. As with many products, manufacturers have begun making systems that approach “idiot-proof” installations.

 TABLE 2.1 Comparison of Various Waterstop Types

PVC waterstops have long been the standard within the construction industry. They are provided in a variety of shapes and sizes for every situation to be encountered, as shown in Fig. 2.16.

FIGURE 2.16 Typical PVC waterstops and their properties.

PVC waterstops with the dumbbell shape in the middle are used for installation where actual movement is expected in the substrate, typically not thermal movement but structural movement. Figure 2.17 shows an expansion joint installation with the bulb portion of the waterstop left exposed to permit movement. However, waterproofing applications require the joint to be filled with a properly designed sealant joint to permit a waterproofing below-grade membrane to run continuously over the joint.

FIGURE 2.17 Use of PVC waterstop in expansion joint.

The problem with PVC waterstops is their susceptibility to improper installation (99% principle) or damage during the concrete placement. The waterstop must be held in place properly during the first half of the concrete placement. This is accomplished by a variety of methods as shown in Figs. 2.18 and 2.19. This situation is not idiot-proof and must be carefully monitored for quality control to ensure that the waterstop remains positioned during both halves of the concrete placement activities. Far too often, the PVC waterstop ends up folded over, preventing it from functioning properly. In addition, workers installing the reinforcing bars will often burn, puncture, or cut the waterstop.

FIGURE 2.18 Placement and securing of waterstops at
construction joints.

FIGURE 2.19 Placement of waterstop for first
half of concrete placement.

In striving to make waterstops idiot-proof, manufacturers have created several alternatives to the PVC standard including many hydrophilic derivatives. These systems, along with the bentonite and asphalt plastic, are used mainly for control joints and not provided for expansion joints. These systems are simple to install, and do not have to be installed in both sections of concrete placements. The material is adhered directly to the edge of the first concrete placement in preparation for the second placement of concrete. Note this detailing in Fig. 2.20 and in the photograph of the installed product, Fig. 2.21.

FIGURE 2.20 Typical installations of hydrophilic or similar waterstop materials

FIGURE 2.21 Installed asphaltic waterstop.

The materials generally expand after being wetted by the water contained in the concrete mixture. This swelling action enables the materials to fill the voids within the joint to form a watertight construction joint. Since these products expand in the presence of water, they must not be wetted prematurely.

This requires that the second concrete placement take place almost immediately after the waterstop placement, otherwise the joint might expand if exposed to rain or dew. The asphalt plastic is not susceptible to moisture like bentonite or hydrophilic materials, but their limited elastomeric capabilities might prevent the complete sealing of the joint if some areas are not bonded properly.

The materials are easily installed in a variety of positions for properly detailing watertight joints below-grade as shown in Fig. 2.22. None is meant for exposure to the elements and must be completely covered by the concrete placement. As such, they present limited expansion capabilities for the substrate. When an expan-
sion waterstop material is required, the PVC or rubber types are required.

FIGURE 2.22 Several recommended uses of hydrophilic waterstop.

Waterstop size is determined by the expected head of water pressure to be encountered at the joint. Table 2.2 summaries the recommended waterstop and minimum depth of embedment into the concrete sub- strate for various head pressures. Actual site conditions vary, and these measurements should be used only as approximations.

 TABLE 2.2 Suggested Waterstop Sizing for General Conditions

Waterstop manufacturers will recommend actual joint design when actual job conditions are submitted for review.

Manufactured Foundation Drainage System Installation.

Material is generally supplied in rolls that is simply applied to the waterproofed walls by using double-sided masking tape, sealant, or other adhesives recommended by the waterproofing membrane manufacturer; see installation photograph, Fig. 2.10. The material is installed like roofing shingles, overlapping in the direction of water flow, starting with the lower portion first, lapping higher elevation goods over the already installed piece to match the manufacturer-supplied flange edges (Fig. 2.11). Drainage systems can also be applied directly to lagging prior to concrete placement (Fig. 2.12).

FIGURE 2.10 Application of drainage system system using termination bar directly over
terminating edge of waterproofing membrane.

FIGURE 2.11 Application of drainage system.

FIGURE 2.12 Drainage system being applied directly to founda-
tion lagging.

The filter fabric material is always  applied facing out, and manufacturers provide additional fabric at ends to overlap all seams. The terminated ends of the material are covered with the fabric by tucking it behind the plastic core sheet. Side edges of the sheet are typically attached together by overlapping and applying an adhesive. Figure  2.13 shows a partially completed drainage system installed with appropriate drain field gravel backfill.

FIGURE 2.13 Installation of drainage field adjacent to foundation for completion of prefabricated
drainage system.

Figure 2.14 details the use of drainage systems for under-slab drainage. Figure 2.15 details the use of these systems for horizontal transitioning to vertical drainage at a below-grade tunnel installation.

Backfilling should take place as soon as possible after installation; using the available site soil is acceptable. Backfill should be compacted as required by specifications using plate vibratory compactors. Caution should be taken during compaction not to damage the fabric material.

FIGURE 2.14 Manufactured drainage system used for below-slab drainage.

FIGURE 2.15 Below-grade tunnel waterproofing using both horizontal
and vertical drainage application.

MANUFACTURED FOUNDATION DRAINAGE SYSTEMS

In addition to the premanufactured foundation and soil drainage systems, there are also available drainage systems used in conjunction with both vertical and horizontal belowgrade waterproofing systems. These drainage systems provide additional protection against water infiltration and effectively reduce hydrostatic pressure against below-grade envelope components.

The products aid in the drainage of groundwater by collecting and conveying the water to appropriate collection points for drainage away from the structure. A simplified typical design is shown in Fig. 2.7.

FIGURE 2.7 Simplified design detailing for premanufactured drainage system.

 The products provide low-cost insurance against water infiltration and should be used with every below-grade waterproofing application (with the possible exception of hydrous-clay materials). More often than not, the drainage systems can be used in lieu of protection board for most membrane applications, effectively negating any additional costs for the system’s superb protection.


Besides the additional drainage protection for occupied spaces, the systems are also used alone for protecting various civil structures such as landfills and retaining walls or abutments. Among the many uses for manufactured drainage systems:

● Below-grade walls and slabs
● Retaining walls and abutments
● Tunnels and culverts
● Lagging
● Embankments
● Landfills
● French and trench drains (described in the previous section)
● Drainage fields for golf courses and other park and play field structures
● Specialized drainage requirements
● Above-grade plaza decks and similar installations

The system is similar to the prefabricated soil drainage systems only available in larger sheets and drainage cores to facilitate drainage.

The material consists of a formed plastic three-dimensional core that acts as the collector and drainage transporter of the water, as shown in Fig. 2.8. The plastic drainage product is also covered with a geotextile fabric to prevent the silt, soil, clay, and sand from clogging the drainage system. The systems usually have some type of plastic sheeting adhered to one side to protect from indenting waterproofing membranes as well as acting as an initial water-proofing system.

FIGURE 2.8 Typical manufactured drainage systems.

The systems not only eliminate the need for protection board, but also eliminate the requirement for special backfill material consisting of sand or gravel materials to promote drainage. Typically, the existing soil is used as backfill material, reducing the overall costs of new construction. A typical below-grade wall detailing, using the drainage as protection for the waterproofing membrane, is detailed in Fig. 2.9.

FIGURE 2.9 Below-grade waterproofing application with drainage board used as
protection.

The systems also provide a drainage flow rate (depending on the size of plastic core structure, which varies from 1 4 in to 1 2 in) 3–5 times the capacity of commonly used drainage back-fill materials such as sand or small aggregate fill. The material is obviously lightweight, with one person capable of carrying the average roll of material that covers as much as 200 ft 2 of substrate, the equivalent of a small dump truck of aggregate backfill.

Materials selected should have a high compressive strength to protect waterproofing applications (a minimum of 10,000 psf). Also, the system should be resistant to any chemicals it might be exposed to, such as hydrocarbon materials at airports.

Among the many advantages of manufactured drainage systems over conventional aggregate backfill:

● Cost effectiveness.
● Attached filter fabric or geotextile eliminates the usual clogging of traditional systems.
● High-strength material can be used in lieu of protection board for membranes.
● Provides belt and suspender protection for below-grade spaces by quickly channeling ground and surface water away from the structure.
● Permits backfilling with the excavated soils.
● Lightweight and idiot-proof installations.

Prefabricated Foundation Drainage System Installation

The product can be laid into preexisting trenches available from foundation construction or trenches constructed specifically for the drainage field. The width of the trench is typically 2–6 in wide. The depth of the trench is determined upon the actual site conditions and soil permeability. Figure 2.6 represents a typical drainage detail.

The prefabricated plastic drains usually permit the excavated soil to be used as back-fill, eliminating the requirement for special backfill material. The backfill must be mechanically compacted in layers.
Geotextile covering is selected based on the soil conditions. Here are the basic geotextiles required for typical soil conditions:

● High clay content—nonwoven needle-punched geotextile
● Sandy soils—woven materials with high permeability
● High silt content—small-opening geotextiles

Soils of any combinations of the above types generally require testing to be performed and specific recommendation by the drainage system manufacturer.

Manufacturer-provided tees, splicing connectors and outlet connectors should be used as designed. The system is designed to collect and drain water in a variety of ways that meet specific site requirements. Drainage can be as simple as outflow to bare soil away from the structure as surface drainage, or it can be designed to outflow into municipal storm drains.

FIGURE 2.6 Typical detailing for foundation drainage system.
(Courtesy of TC Mira DRI)

PREFABRICATED FOUNDATION AND SOIL DRAINAGE SYSTEMS

These field-constructed foundation drainage systems are obviously very difficult to build properly and often perform poorly over time due to infiltration into the drainage piping by silt, sand, and soil that will eventually clog the entire system. Manufacturers have responded by developing “idiot-proof” systems to replace these now-antiquated field constructed systems. These prefabricated systems are relatively inexpensive and make them completely reasonable for use as additional water control for practically any construction project including residential, multifamily, commercial, and civil structures. These systems add superior protection for minor costs to any project. For example, concrete slabs without reinforcing can withstand hydrostatic pressure equal to approximately 2.5 times the slab’s thickness. In practically every structural design, it becomes much more economical to add under-slab drainage than to increase the thickness of the slab.

Prefabricated plastic soil drainage systems are available from a number of manufacturers. These products are manufactured in a variety of plastic composite formulations including polypropylene, polystyrene, and polyethylene. Figure 2.2 pictures a typical manufactured drainage product. The systems combine specially designed drainage cores covered with geotextile fabric in prepackaged form that eliminates all field construction activities except trenching and backfilling operations.

FIGURE 2.2 Typical foundation premanufac-
tured drainage system with geotextile attached.

The systems are idiot-proof in that the product is merely laid into the area designated for a drainage field. Only appropriate sloping of the trench to collection points is required. Figure 2.3 presents a simplified isometric detail of a drainage system installation. The product is puncture- resistive to protect its performance during backfill. Manufacturers also provide ample accessories (including termination and transition detailing) to complete the installation. Figures 2.4 and 2.5 show available accessories including a tee connection to join one branch of a drainage to another, and an outlet connection for collection of water that terminates at a drain box or culvert.

FIGURE 2.3 Isometric detail of drainage system.
(Courtesy of American Wick Drain Corporation)

FIGURE 2.4 “T” connector for drainage system.
(Courtesy of American Wick Drain Corporation)

FIGURE 2.5 Outlet connection for drainage sys-
tem. (Courtesy of American Wick Drain
Corporation)

Materials are available in a variety of widths (up to 36 in) and lengths provided in rolls of up to 500 ft long. The product should be puncture-resistant with some elongation capability for movement after installation, and be resistant to the natural or human-made elements to be found within the intended service area.

Prefabricated Foundation Drainage System Installation The product can be laid into preexisting trenches available from foundation construction or trenches constructed specifically for the drainage field. The width of the trench is typically 2–6 in wide. The depth of the trench is determined...

GROUNDWATER CONTROL: protect interior areas.

Water present at below-grade surfaces is available from two sources—surface water and groundwater. Beyond selection and installation of proper waterproofing materials, all waterproof installations must include methods for control and drainage of both surface and groundwater.

Surface water from sources including rain, sprinklers, and melting snow should be directed immediately away from a structure. This prevents percolation of water directly adjacent to perimeter walls or water migration into a structure. Directing water is completed by one or a combination of steps. Soil adjacent to a building should be graded and sloped away from the structure. Slopes should be a minimum of  1 2 in/ft for natural areas, paved areas, and sidewalks sloped positively to drain water away from the building.

Automatic sprinklers directed against building walls can saturate above-grade walls causing leakage into below-grade areas. Downspouts or roof drains, as well as trench drains installed to direct large amounts of water into drains, direct water away from a building. Recommended controls for proper water control are summarized in Fig. 2.1.

FIGURE 2.1 Below-grade drainage detailing.

CONSTRUCTION - BELOW-GRADE WATERPROOFING

INTRODUCTION

Water in the form of vapor, liquid, and solids presents below-grade construction with many unique problems. Water causes damage by vapor transmission through porous surfaces, by direct leakage in a liquid state, and by spalling of concrete floors in a frozen or solid form.

Water conditions below-grade make interior spaces uninhabitable not only by leakage but also by damage to structural components as exhibited by reinforcing steel corrosion, concrete spalling, settlement cracks, and structural cracking.

Below-grade waterproofing materials are subject to water conditions that are typically more severe than above-grade envelope areas. Structure elements below-grade are often exposed to hydrostatic pressure from ground water tables that can rise significantly during periods of heavy rainfall. At the same time, below-grade materials are not subject to the harsh environmental conditions of exposed envelope components, including wind-driven rain, ultraviolet weathering, and acid rain.

Manufacturers of below-grade waterproofing systems can then concentrate on the properties to ensure effective barriers to water penetration without having to contend with the elements encountered above-grade. For example, membranes used below-grade can have substantial elongation properties since the manufacturer does not have to supplement the product with ultraviolet resistant properties that tend to limit elongation capabilities.

Below-grade systems are all barrier systems; there are no appropriate new construction drainage systems designed for adequate protection under hydrostatic pressure. Diversion systems are frequently included in the design of below-grade waterproofing, and in fact are highly recommended for use in conjunction with any below-grade system, with the possible exception of hydrous clay materials that require the presence of adequate water supply to maintain their hydration and waterproofing properties.

Proper below-grade design begins with adequate control of water conditions. There is no reason to subject any below-grade envelope components to unnecessary amounts of water that could otherwise be diverted away form the structure for supplementary protection. Both surface and groundwater should be diverted immediately away from the structure at all times.

SUCCESSFUL ENVELOPE CONSTRUCTION

For envelopes to function as intended requires proper attention to

● Selection and design of compatible materials and systems
● Proper detailing of material junctions and terminations
● Installation and inspection of these details during construction
● Ability of composite envelope systems to function during weathering cycles
● Maintenance of the completed envelope by building owners

From the multitude of systems available to a designer, specific products that can function together and be properly transitioned must be chosen carefully. Once products are chosen and specified, proposed substitutions by contractors must be thoroughly reviewed.

Similar products may not function nor be compatible with previously chosen components. Substitutions of specified components with multiple, different systems only further complicate the successful installation of a building envelope.

Improper attention to specified details of terminations, junctures, and changes in materials during installation can cause water infiltration. Once construction begins, installation procedures must be monitored continuously to meet specified design and performance criteria and manufacturers’ recommendations. Detailing problems compound by using several different crafts and subcontractors in a single detail. For instance, a typical coping cap detail (Fig. 1.10) involves roofing, carpentry, masonry, waterproofing, and sheet metal contractors. One weak or improperly installed material in this detail will create problems for the entire envelope.

FIGURE 1.10 Typical coping cap detailing and the subcontractors involved.

Finally, products chosen and installed as part of a building envelope must function together during life-cycling and weathering of a structure. For example, an installed precast panel might move over 1 2 in during normal thermal cycling, but the sealant installed in the expansion joint might be capable of withstanding only  1 4-in movement.

Proper maintenance after system installation is imperative for proper life-cycling.

Will shelf angles be adequate to support parapet walls during wind or snow loading?
Will oxidation of counterflashing allow water infiltration into a roof system, causing further deterioration?

From these processes of design, construction, and maintenance, 99 percent of a building envelope typically will function properly. The remaining 1 percent creates the magnitude of problems. This 1 percent requires much more attention and time by owners, architects, engineers, contractors, and subcontractors to ensure an effective building envelope.

The most frequent problems of this 1 percent occur because of inadequate detailing by architects, improper installation by contractors and subcontractors, and improper maintenance by building owners. Typical frequent envelope errors include

● Architects and engineers. Improper detail specifications (90%/1% principle); no allowance for structural or thermal movement; improper selection of materials; use of substitutes that do not integrate with other components of the envelope.
● Component manufacturers. Insufficient standard details provided for terminations and transitions; inadequate training for installers of materials; insufficient testing for compatibility with other envelope components.
● General contractors and subcontractors. Improper installations (99% principle); inattention to details; no coordination between the various envelope subcontractors; use of untrained mechanics to complete the work.
● Building owners and managers. No scheduled maintenance programs; use of untrained personnel to make repairs; no scheduled inspection programs; postponement of repairs until further damage is caused to the envelope and structural components.

Manufacturers are now concentrating on making technological improvements in the materials themselves rather than technological advances, specifically making their products “idiot-proof.” They realize that meeting industry standards does not correlate with success in field applications. In reality, products are subjected to everything that can possibly go wrong, from environmental conditions during installation to untrained mechanics installing the product. Never are products installed in the pristine conditions of a laboratory.

Making their products with “belt and suspenders” protection increases the likelihood of success, at least for the individual system—for example, products that no longer require primers, no mixing of two component materials but now one-part materials, pressure rinse versus pressure-wash preparation, and 300% elongation rather than 100% to add additional protection against excess movement or in-place service requirements.

Similar quality advances at the job-site level by contractors to adequately apply the precautions necessary to protect against the 90%/1% and 99% principles will eliminate the vast majority of waterproofing problems that now plague the industry.