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Community and Q&A

Should I consider using waterproof concrete for my foundation?

user-271879 | Posted in Energy Efficiency and Durability on

I have been looking carefully at my options for waterproofing the basement foundation of my future house in Vermont. I expect that the foundation will experience periods of hydrostatic pressure, so I am looking for the best waterproofing system with reasonable costs (e.g. up to $4000). I will, of course, install footing drains and a free draining layer on the outside of the foundation, and until recently I was planning to use a professionally applied elastomeric spray-on waterproofing product. However, I just heard about Waterproof Concrete and it seems like the integral permeability-reducing admixtures (PRAs) could be better approach than a surface barrier treatment. I discovered that the two best PRAs for concrete exposed to hydrostatic pressure (PRAHs) are hydrophobic chemicals, like those made by Hycrete, and microcrystalline products such as those made by Kryton. I don’t know yet whether any PRAH will be available for me to use, but before I make the effort to find out, I have lots of questions about waterproof concrete. Are PRAHs really as good as the companies make them sound? Is one type of PRAH better than the other? What are their costs – relevant to each other and to surface barrier treatments? Have they proven themselves in the field, especially over longer periods of 20+ years? Are they better than surface barriers – in the short term or the long term? Can you safely omit a surface barrier treatment when using a PRAH, like the companies claim, thus offsetting the cost of the PRAH?

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  1. Expert Member

    Crystallizing admixtures are a very effective way to keep foundation walls dry. Find out from your concrete batch plant which ones they use. Around here it is usually Xypex. It's worth remembering that the weak points still remain: That is the slab/footing intersection and all penetrations, including where the concrete ties were. I'd still use some sort of exterior damp-proofing as good insurance.

  2. user-271879 | | #2

    Thanks Malcolm. I forgot to mention that I am planning to include a PVC waterstop to bridge the gap between the footing and the wall. They are a pain for the concrete guys to set in the footing, but do a great job sealing this cold joint.

  3. Expert Member

    Timothy, Several weeks ago I poured a large foundation with three Diyers. One truck had too stiff a mix, but the guy filling the forms didn't know enough to complain, and his friend using the vibrator was so afraid of getting caught up on the rebar he didn't do a very good job. The result was some honeycombing and voids. We sealed the walls with a crystallizing slurry and they are bone dry, even in the heavy rains we have had. Over the years Xypex has saved me a lot of grief.

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