Prescott, AZ

Root Cellar

Today I applied the first coat of waterproofing to the crawl space walls. I'm using two coats of Deco 20 Seal Waterproofing. First I applied one layer of stucco about 3/8" thick, directly onto the Perfect Block (well wetted first). I used LaHabra Fastwall Sanded Base stucco mix; it took 17-1/2 bags to cover 400 SF, 80 lbs each.

Dan at Deco Products told me I could apply his coating directly to the Perfect Block; they also recommend it for white EPS ICF block, also applied directly. However I wanted to make sure the block surface was well sealed and also mechanically protected, so I applied the stucco.

Attached are before and after photos of the foundation.I will backfill to within 6 inches of the concrete deck you see here. My stucco work is not the prettiest, but only the top six inches will be visible above grade, and the bottom four feet will get covered by "dimple board" before backfilling. My perimeter footing drains, with stone, fabric, and perforated pipe, are already in place, below the top of the footing. The plastic film being held down by rocks is the vapor barrier I placed under the slab and integral footings; it's scrim-reinforced 10-mil polyethylene.

After applying the second coat of Deco 20 Seal, I will trim that plastic to about five inches wide and lap it inward over the top of the footing, and embed it in a thick layer of Deco. I don't think I'll have any moisture problems in this cellar!!

Today is exactly three weeks since the pour; like I said, I work pretty slowly! It will be another week before it's backfilled, so I guess the concrete will have reached its 28-day strength by then.

The decking is called W3 by Verco. It is readily available for large and small projects from the Myers Group in Tempe The folks there are great to work with and you can drop my name if you contact them. This composite decking has undulations that are 3" high on 12" centers, and each sheet is 36" wide. Myers Group will cut it to length and even do your take-off from your floor plans.

This decking is considered composite because the concrete keys into embossed features, so that the steel acts like rebar and takes the tensile stress while the concrete handles the compressive stress.

I used 18-gauge, as they have it in stock. Verco publishes a PDF catalog with all the design info you would need. I could have gotten by with 20-gauge however.




Basically you need to deal with two span ratings, final after curing, and unshored during the pour.

The catalog gives both in tables as a function of total concrete thickness. In my case the final load capacity will be 130 PSF (!), and the maximum unshored span was 13 ft. That's why I needed the temporary shoring wall down the middle, as my full floor span is just over 14 feet.