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Bentonite Waterproofing Panel Self-Healing Swell Thickness Calculator

Calculate the hydrated (swollen) gel thickness a bentonite waterproofing panel forms when it absorbs water.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-27 · v1.1.0

Market
Imperial · sales tax

Hydrated (swollen) gel thickness

2.46 in

Check your inputs

Swell factor varies by bentonite grade and confinement condition — this is a general reference figure. Bentonite panels require adequate confining pressure (backfill or structural confinement) to develop their full sealing performance; unconfined swell can behave differently.

Dry (unhydrated) thickness
0.25 in

With the figures above, the hydrated (swollen) gel thickness comes to 62.5 mm. Behind that figure, dry (unhydrated) thickness is the biggest single quantity at 6.25 mm; start there if the total looks wrong. The method behind this is well established, though site conditions and material batches will move it somewhat. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Add the equipment this sizes

This result is a specification — 2.461 in — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Dry bentonite layer thickness = bentonite content per area ÷ dry density; hydrated bentonite clay swells dramatically when wetted (commonly cited swell factors of roughly 10-15x by volume) to form a self-healing, low-permeability gel that seals small punctures and cracks

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Frequently asked questions

Why does bentonite need to swell so much to be effective?
The dramatic volume increase when bentonite clay hydrates — commonly 10-15x by volume — is what lets it close small punctures, seams, and cracks in the waterproofing layer, forming a continuous, low-permeability gel where the dry panel alone would leave gaps.
Does the swell factor stay the same for every project?
No — it varies by bentonite grade and by confinement condition. This calculator uses whatever swell factor you enter as a general reference figure, so check the manufacturer's data for your specific product grade.
Does bentonite swell fully without backfill in place?
Not necessarily. Bentonite panels need adequate confining pressure, typically from backfill or structural confinement, to develop their full sealing performance — unconfined swell can behave differently than the confined swell factor assumed here.