BUILDER'S ENGINEER: SHEET WATERPROOFING SYSTEM APPLICATION

Unlike liquid-applied systems, broom-finished concrete is not acceptable, as coarse finishes will puncture sheet membranes during application. Concrete must be smoothly finished with no voids, honeycombs, fins, or protrusions. Concrete curing compounds should not contain wax, oils, or pigments. Concrete surfaces must be dried sufficiently to pass a mat test before application.

Wood surfaces must be free of knotholes, gouges, and other irregularities. Butt joints in wood should be sealed with a 4-in-wide membrane detail strip, then installed. Masonry substrates should have all mortar joints struck flush. If masonry is rough, a large coat of cement and sand is required to smooth surfaces.

Metal penetrations should be cleaned, free of corrosion, and primed. Most systems require priming to improve adhesion effectiveness and prevent concrete dust from interfering with adhesion (Fig. 2.65).

FIGURE 2.65 Applying primer to concrete substrate in
preparation for sheet system.

All sheet materials should be applied so that seams shed water. This is accomplished by starting at low points and working upward toward higher elevations (Fig. 2.66). With adhesive systems, adhesives should not be allowed to dry before membrane application. Self-adhering systems are applied by removing a starter piece of release paper or polyethylene backing, adhering membrane to substrate (Fig. 2.67).

FIGURE 2.66 Application of sheet membrane.

FIGURE 2.67 Removing release paper backing from
self-adhering sheet membrane.

With all systems, chalk lines should be laid for seam alignment. Seam lap requirements vary from 2 to 4 in (Fig. 2.68). Misaligned strips should be removed and reapplied, with material cut and restarted if alignments are off after initial application. Attempts to correct alignment by pulling on the membrane to compensate may cause “fish mouths” or blisters.

FIGURE 2.68 Seam lap detailing for sheet membranes.

A typical sheet membrane application is shown in Fig. 2.69.

FIGURE 2.69 Typical sheet membrane application detailing.

At changes in plane or direction, manufacturers call for a seam sealant to be applied over seam end laps and membrane terminations (Fig. 2.70). Materials are back-rolled at all seams for additional bonding at laps (Fig. 2.71). Any patched areas in the membrane should be rolled to ensure adhesion.

FIGURE 2.70 Applying mastic termination detailing.

FIGURE 2.71 Back-rolling membrane at seams to
ensure bonding.

Each manufacturer has specific details for use at protrusions, joints, and change in plane (Fig. 2.72). Typically, one or two additional membrane layers are applied in these areas and sealed with seam sealant or adhesive (Fig. 2.73). Small detailing is sealed with liquid mem- branes that are compatible and adhere to the sheet material. Figure 2.74 details a typical col- umn foundation waterproofing application. Figure 2.75 shows the proper treatment of a control or expansion joint using sheet systems.

FIGURE 2.72 Transition detailing for sheet membranes.

FIGURE 2.73 Applying reinforcement strips at transition
details.

FIGURE 2.74 A column foundation waterproofing detail.

FIGURE 2.75 Expansion joint treatment using sheet system

Protection systems are installed over membranes before backfilling, placement of rein- forcing steel, and concrete placement. Hardboard, 1 8–1 4-in thick, made of asphalt-impregnated material is used for horizontal applications. Vertical surfaces use polystyrene board, 1 2-in thick, which is lightweight and applied with adhesives to keep it in place during back-fill. Sheet systems cannot be left exposed, and backfill should occur immediately after installation.

Protrusions through the membrane must be carefully detailed as shown in Fig. 2.76.

FIGURE 2.76 Protrusion detailing for sheet systems.

Manufacturers require an additional layer of the sheet membrane around the penetration that is turned on or into the protrusion as appropriate. A bead of sealant or mastic is applied along the edges of the protrusion. For expansion joints in below-grade walls or floors, the installation should include appropriate waterstop and the required additional layers of membrane (Fig. 2.77). Sheet systems must be terminated appropriately as recommended by the manufacturer. Termination details prohibit water from infiltrating behind the sheet and into the structure. Termination bars are often used as shown in Fig. 2.78. Reglets can be used (Fig. 2.79); these also permit the termination of above-grade waterproofing in the same reglet that then becomes a transition detail.