Root cellar construction advice — concrete additive?
Hello! This summer we are building a greenhouse addition with an underground root cellar attached. In one of the root cellar books I read, they recommend Everdure Caltite as an additive in concrete to make the foundation waterproof. What are your recommendations?
We will be putting a poured concrete slab over corrugated metal for support for the roof which will form a patio on top for us to enjoy outside, for which, some sort of waterproofing agent makes sense to me. Would you use this product on the foundation and the roof? Would you use it in the greenhouse addition foundation? Is there something else you would do or use instead? Is it costly?
Thanks,
Leah
P.S. I would love it if GBA created a guide to building root cellars!
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Replies
Leah,
I am not familiar with Everdure Caltite. The manufacturer's website describes the product as appropriate for waterproof concrete decks and roofs. It appears to be used mostly in commercial construction, so it may be difficult to find a residential contractor who is familiar with the product.
Your question has been discussed on the GBA site before. You can read an earlier thread here: Waterproof a concrete slab roof which serves as a roof-top deck.
A concrete additive like Everdure Caltite is not the only way to produce a waterproof concrete roof. Other systems use dimple mats and membranes. Several manufacturers offer systems to create waterproof concrete roofs, including:
W. R. Meadows
Ames Research Laboratories
Desert Brand.
If you want to install a waterproof concrete roof, you need to find an experienced contractor who has installed such a roof before, and who will stand behind his or her work. Finding such a contractor is the key; which system the contractor uses is secondary.
Finally, it should be pointed out that not all root cellars require a waterproof concrete roof. Root cellars can also have conventional above-grade sloped roofs -- an approach that probably costs less and will have fewer problems than the approach you are considering.