The article "Basics of Residential Slab-on-ground Construction" (January issue, page 21), ignored the problem of how to transport concrete across the vapor barrier and welded wire mesh without puncturing the vapor barrier. This latter would be a problem on large pours where the truck-mixer chute will not reach . How do you solve this problem?
In most small jobs it is not necessary to transport the concrete across the vapor barrier from the truck-mixer chute, and for this reason the subject was not discussed in the article you refer to. A Portland Cement Association Information Sheet called "Concrete Floors on Ground for Residential Construction" describes a system of using a stiff grout and a membrane dampproofing layer over the coarse aggregate. The system should be less susceptible to puncturing than polyethylene. A stiff grout coat at least 1/2 inch thick is placed over the compacted granular fill to provide a smooth surface for the membrane. The grout is 1 part portland cement, 3 parts sand, and enough water to make a stiff mix. This is broomed or floated in place. After it has hardened and dried, hot asphalt is mopped over the grout coat as well as over any bearing partition footings. At the same time as the asphalt is being mopped on, a layer of 15-pound asphalt-saturated roofing felt is placed on it, lapping the edges over one another. Another layer of asphalt is put down, then a second layer of roofing felt, and a final top coating of asphalt. The membrane should be continuous over the whole area and should continue up on the inside of the foundation walls to at least 1 inch above the finished floor level. This membrane is more resistant to puncturing than polyethylene, but workmen should nevertheless be cautioned to take care not to puncture it during concreting.