My Mother's House Part III
(Page 2 of 4)
November/December 1981
By the Mother Earth News staff
We found that the EPDM waterproofing wasn't much more difficult to lay down than a carpet in one's living room. The cut-to-length rolls can be relatively heavy (ours weighed about 400 pounds) . . . but once the burden is positioned, unfurling is easy.
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After it's spread in place, the membrane must be squared up, smoothed, and thoroughly sealed—with rubber cement—along all of its edges. We lapped the sheet up both the parapet and the second story wall of our building, cemented it along both sides, and then applied flashing to insure that a minimum of water would get to the seal. (The edge—securing process is particularly important, since a leak along the perimeter could allow water to migrate beneath the rubber and appear at some other point inside the house. Tracking down such a problem can be quite difficult.)
MUD ON THE WALLS
Though elastomeric membranes can be used on walls, the procedure required in such cases is considerably more difficult than is that used when working on a horizontal surface. The weight of the material makes rolling it up (or down!) a wall a struggle, and the difficulty is increased by the need to prevent the rubber from being stretched (since it will eventually return to its original size). In addition, the sheets must be affixed to the vertical surface as they're put up.
We considered several different materials for waterproofing our bermed walls, but—after studying the properties of the various products—decided to try a trowel—on bentonite clay produced by Effective Building Products, Inc. (Dept. TMEN, 28001 Chagrin Boulevard, Suite 207, Cleveland, Ohio 44122). As described by the Bentonize system patent holder, Dr. Bryan "Mac" McGroarty, bentonite is a clay mineral which was created-geologists speculateas the result of a series of violent volcanic explosions that took place in the Aleutian Islands about 150,000,000 years ago. It is thought that winds carried the ash from the eruptions in a southeasterly direction, and that the material was eventually deposited in a highly alkaline sea which then existed in the Black Hills region of South Dakota and Wyoming.
Bentonite is valuable, in today's marketplace, primarily because of its remarkable reaction to water: An electrical charge, which is an inherent property of the platelike structure of sodium montmorillonite (the particular form of bentonite used to make Bentonize), is partially discharged to surrounding water ... which causes the plates to separate slightly, producing a gelling of the material. Therefore, bentonite clays tend to absorb a small amount of water—which could cause the mineral to expand to as much as 22 times its normal size if it were unconfined-and then become nearly impervious to further penetration by the liquid.
