Bentonite waterproofing
When does bentonite waterproofing suit a foundation?
Bentonite waterproofing can suit a below-grade foundation when the selected system has proper confinement and compatible groundwater. As of Nov 2026, CETCO’s VOLTEX data sheet makes those conditions central; swelling clay is not a universal inside-wall coating or a substitute for a complete foundation detail.
Sources: CETCO / Minerals Technologies. Checked Nov 4, 2026.
By Waterproofing Cost
Published · Updated
What makes a confined bentonite system work?
CETCO’s sheet describes sodium bentonite held between geotextiles. The installed system relies on confinement; it is a designed foundation membrane rather than loose clay spread over an exposed basement wall.
Which site and wall conditions can rule it out?
The opened VOLTEX edition excludes masonry-block foundation walls and expansion-joint sealing. It also requires groundwater compatibility review in specified chemical or salt conditions. These are product-specific limits, not a claim about every bentonite formulation.
Confirm wall material and groundwater conditions against the specified product edition.
What details must the system proposal resolve?
Ask to see substrate preparation, seams, penetrations, grade termination and the required confinement in the project drawings. CETCO gives separate details for these transitions; naming the field membrane leaves the interfaces unresolved.
Identify who will inspect the interfaces before concealment.
How should you judge the complete foundation scope?
PNNL treats wall protection, drainage planes and water removal as coordinated parts of foundation water management. Compare the foundation scope with the general wall-method choices before pricing excavation and restoration.
For outdoor drain or runoff planning, use the sister site’s existing exterior foundation drainage guide. Keep that scope separate from selecting the waterproofing material.
Frequently asked questions
Is loose bentonite the same as a specified sheet system?
No. This guide concerns a manufactured system with installation details and confinement requirements. A loose-clay or injection proposal needs its own applicable specification.
Does the opened VOLTEX sheet permit block foundation walls?
No. That edition says not to use VOLTEX on masonry-block foundation walls. Confirm another proposed product against its own instructions.
Does the calculator supply a bentonite-specific price?
No. Its general membrane reference does not identify a bentonite product or include a complete excavation and restoration project. Obtain a system-specific proposal.
Sources and dates
Key facts checked . Recorded calculator components retain their original Oct 24, 2026 retrieval date; new technical references were accessed separately for each article.
- VOLTEX Bentonite Geotextile Waterproofing System: Technical Data — CETCO / Minerals Technologies. Source publication: 2025-03 (V8). Accessed Nov 4, 2026.
- Foundation Wall Water/Damp-Proofing — PNNL Building America Solution Center. Source publication: not stated. Accessed Nov 4, 2026.
See the full source inventory and calculation limits.
Plan the next step
Get a written suitability decision and the confinement and transition details. Use the calculator only as a separate general planning reference.