SHEET MEMBRANE WATERPROOFING SYSTEMS

Thermoplastics, vulcanized rubbers, and rubberized asphalts used in waterproofing applications are also used in single-ply roofing applications. Although all systems are similar as a generic grouping of waterproofing systems, consider their individual characteristics whenever you choose systems for particular installations.

Sheet membranes have thickness controlled by facto manufacturing. This ensures uniform application thickness throughout an installation. Sheet manufactured systems range in thickness from 20 to 120 mil. Roll goods of materials vary in width from 3 to 10 ft.

Larger widths are limited to horizontal applications, because they are too heavy and difficult to control for vertical applications.

Unlike liquid systems, sheet system installations involve multiple seams and laps and are not self-flashing at protrusions and changes in plane. This is also true for terminations or transitions into other members of the building envelope.

Applications below grade require protection board during backfill operations and concrete and steel placements. Fins and sharp protrusions in substrates should be removed before application, or they will puncture during installation. Materials used in vertical applications should not be left exposed for any length of time before backfilling.

Weathering will cause blistering and disbonding if backfill operations must begin immediately after membrane application.

Vertical single-ply applications are more difficult than fluid applications, due to the difficulty of handling and seaming materials. Seams are lapped and sealed for complete

waterproofing. In small, confined areas such as planter work, vertical installation and transitions to horizontal areas become difficult and extra care must be taken.

Thermoplastics
Thermoplastic sheet-good systems are available in three compositions: PVC, chlorinated polyurethane (CPE), and chlorosulfonated polyethylene (CSPE), which is referred to as hypalon. Materials are manufactured in rolls of varying widths, but difficulty with vertical applications makes smaller widths more manageable.

On horizontal applications, wider roll widths require fewer seams; therefore, it is advantageous to use the widest workable widths. All three systems adhere by solvent- based adhesives or heat welding at seams.

PVC membranes are available in thicknesses of 30–60 mil. CPE systems vary by as much as 20–120 mil, and hypalon materials (CSPE) are 30–35 mil. All derivatives have excellent hydrostatic and chemical resistance to below-grade application conditions. PVCmembranes are generically brittle materials requiring plasticizers for better elastomeric properties, but elongation of all systems is acceptable for below-grade conditions.

Vulcanized rubbers
Vulcanized rubbers are available in butyl, ethylene propylene diene monomer (EPDM), and neoprene rubber. These materials are vulcanized by the addition of sulfur and heat to achieve better elasticity and durability properties. Membrane thickness for all rubber systems ranges from 30–60 mil. These materials are nonbreathable, and will disbond or blister if negative vapor drive is present.

As with thermoplastic materials, vulcanized rubbers are available in rolls of varying widths. Seam sealing is by a solvent-based adhesive, as heat welding is not applicable. A separate adhesive application to vertical areas is necessary before applying membranes.

Vulcanized rubber systems incorporate loosely laid applications for horizontal installations.

Although other derivatives of these materials, such as visquene, are used beneath slabs as dampproofing membranes or vapor barriers, they are not effective if hydrostatic pressure exists. Material installations under slabs on grade, by loose laying over compacted fill and sealing joints with adhesive or heat welding, are useful in limited waterproofing applications.

This is a difficult installation procedure and usually not specified or recommended.

Loosely laid applications do, however, increase the elastomeric capability of the mem- brane, versus fully adhered systems that restrict membrane movement.

Rubberized asphalts
Rubberized asphalt sheet systems originally evolved for use in pipeline protection applications. Sheet goods of rubberized asphalt are available in self-adhering rolls with a  polyethylene film attached. Self-adhering membranes adhere to themselves, eliminating the need for a seam adhesive. Sheets are manufactured in varying widths of 3–4 ft and typically 50-ft lengths.

Also available are rubberized asphalt sheets reinforced with glass cloth weave that require compatible asphalt adhesives for adhering to a substrate. Rubber asphalt products require a protection layer, to prevent damage during backfill or concrete placement operations.

Self-adhering asphalt membranes include a polyethylene film that acts as an additional layer of protection against water infiltration and weathering. The self-adhering portion is protected with a release paper, which is removed to expose the adhesive for placement.

Being virtually self-contained, except for primers, this system is the simplest of all sheet materials to install. Figure 2.64 details a typical below-grade installation.

FIGURE 2.64 Below-grade sheet waterproofing system detailing.

Self-adhering membranes are supplied in 60-mil thick rolls, and accessories include compatible liquid membranes for detailing around protrusions or terminations. Rubberized asphalt systems have excellent elastomeric properties but are not used in above-grade exposed conditions. However, membrane use in sandwich or split-slab construction for above-grade installations is acceptable.

Glass cloth–reinforced rubber asphalt sheets, unlike self-adhering systems, require no concrete curing time. Separate adhesive and seam sealers are available. Glass cloth rubber sheets are typically 50 mil thick and require a protection layer for both vertical and horizontal applications. Typical properties of sheet materials are summarized in Table 2.6.