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.