Manufactured stone needs to drain
The cover article in the December/January issue, "Working With Manufactured Stone" (FHB #192) overlooks one of the mysterious details: how the stone meets, or does not meet, the ground. At the Cultured Stone Web site (www.culturedstone.com), Owens Corning makes it clear that the stone may not touch the ground. A separation distance of not less than 4 in. must be maintained (2-in. separation from pavement). Manufactured stone is more like stucco in this regard than stone. Ground contact prevents rain-soaked manufactured stone from draining.
Visually, this is quite a problem. What does the author recommend occur in this 4-in. gap between the bottom of the stone and the ground? What happens when the ground slopes along the building line? Does the line along the bottom of the stone slope, too? This issue certainly undermines the “real” appearance of the stone.
—Joel Schwartz, via email
Author Brendan Mostecki replies: You’re right; manufactured stone should never be in contact with the grade, a guideline that I should have stated clearly. The stone installation featured in the article was part of a whole-house remodeling project that included excavating around the foundation and backfilling with crushed rock 2 ft. to 3 ft. out from the foundation in lieu of roof gutters. The crushed rock beneath the manufactured stone allows it to drain.
We used the existing grade to start our base course in some areas, and in others, we used 2x4s to elevate the stone above grade. The stone definitely follows the grade, and in some locations, our customers did not want a 4-in. foundation reveal. They wanted the stone down to grade on piers, stairs, and the front of the home.
All contractors, including masons, are in the catering business. We want happy customers, so we cater to them. I always point out that the manufacturer does not recommend the stone coming down to grade, nor do I. But I believe the crushed-rock backfill eliminates much likelihood of a problem.