In floor construction where welded wire fabric and a vapor barrier are used, is there any method of setting screeds without puncturing the vapor barrier?

We have specified that 6-mil polyethylene be used and all laps sealed. Where screed stakes are used, for example, with screeds 10 feet on centers and screed supports 5 feet on centers, patching of the polyethylene is seldom done properly and the vapor barrier can't do its job. Consequently we absolutely prohibit piercing the polyethylene with screed stakes. But contractors complain that it is impossible to hold the screeds on "mud pies." Is there a simple, direct solution to the placing of screed supports without damaging the integrity of the vapor barrier?

There is an adjustable screed support that does not require stakes. It is made by the Skreed'L Company, Post Office Box 3038, Paducah, Kentucky 42001. Perhaps there are other similar products. A successful method has been reported by Fred Herlev, of Read Jones Christoffersen Ltd., Vancouver, British Columbia, which makes use of ordinary job materials. A continuous 1- by 6-inch board is nailed to the tops of 2- by 2-inch stakes so that the top of the board will be flush with the top of the gravel subbase (see diagram). This serves first as a guide for leveling the gravel. Then after a vapor barrier has been placed over it, the board serves as a support for screed support chairs of the type used for suspended slabs. Instead of a continuous board, a 1- by 6- by 6-inch board can be nailed to the top of each stake if preferable, using one stake and board for each screed support chair.We also call your attention to a method of using mud pies to support screed pipes described by John Taylor in his letter to the Editor, "Supporting Screeds on Vapor Barriers," June 1978, page 356.