Four main product categories waterproof a concrete block wall, and each suits a different application. This guide compares them by cost, use case, and durability, so you can match the product to the job instead of over-specifying (and overpaying) or under-specifying (and having it fail).
For the full explanation of why concrete blocks need treatment at all, see our guide to whether concrete blocks are waterproof.
Waterproof Paints and Sealants
Acrylic-latex and elastomeric coatings create a flexible, waterproof film on the block surface, penetrating surface pores whilst forming a protective barrier. They are the lowest-cost option per m² and the easiest to apply by brush or roller, making them suitable for DIY.
Best for: above-ground walls with low water pressure, such as garden walls, boundary walls, and internal applications. Not rated for basement hydrostatic pressure.
Cementitious Coatings
Cement-based slurries applied like thick plaster, bonding chemically with the concrete block substrate. They cure to form a rigid, integral waterproof barrier that can withstand significant hydrostatic pressure, at a higher material and labour cost than paints due to the thicker, multi-coat application.
Best for: basements, retaining walls, and any wall facing sustained water pressure. See our basement waterproofing guide for the full below-ground specification.
Silicate Densifiers
Silicate densifiers work differently to the other three categories. Rather than forming a surface film, they react chemically with the concrete to fill pores and reduce dust and porosity from within. They do not create a flexible waterproof membrane, so they suit low-moisture applications like floors more than walls facing direct water exposure.
Best for: concrete floors and low-moisture masonry, not a substitute for a dedicated wall waterproofing system.
Membrane Systems
Sheet or liquid-applied membrane systems stop water before it reaches the block at all, rather than managing it once it arrives. They cost the most per m² of the four categories, reflecting both material and specialist installation, but suit the most demanding below-ground and high-water-table applications where a coating alone is not enough.
Best for: demanding basement conversions, retaining structures, and sites with a high water table.
Which Should You Choose?
| Product | Relative cost | Best for |
|---|---|---|
| Waterproof paint / sealant | Lowest | Above-ground, low water pressure |
| Cementitious coating | Medium | Basements, retaining walls |
| Silicate densifier | Low-medium | Floors, low-moisture masonry |
| Membrane system | Highest | Demanding below-ground applications |
Frequently Asked Questions
What is the cheapest way to waterproof a concrete block wall?
Acrylic-latex or elastomeric waterproof paint is generally the lowest-cost option and suits above-ground walls with low water pressure, such as garden and boundary walls. It is not rated for basement hydrostatic pressure.
Are silicate densifiers the same as waterproof sealants?
No. Silicate densifiers react chemically with the concrete to reduce porosity and dust, but they do not form a flexible waterproof film the way paints and elastomeric coatings do. They suit floors and low-moisture applications rather than walls facing direct water exposure.
How much does it cost to waterproof a concrete block wall?
Material cost varies widely by product and coverage: waterproof paints and sealants are the cheapest per m², cementitious coatings cost more due to thicker application, and membrane systems cost the most but suit the most demanding below-ground applications. Get quotes for your specific wall area and application before comparing products directly.
Which product lasts longest?
Properly applied cementitious coatings and membrane systems tend to outlast elastomeric paints, often reaching the top of the 10-25 year range quoted for quality waterproofing systems. Surface preparation affects lifespan more than the product choice within any given category.
Specify Waterproofing at the Concrete Stage Too
Surface sealants work alongside, not instead of, a low-permeability concrete mix. Procon 24/7's domestic and commercial concrete services include waterproof admixture mixes across Yorkshire and the North West, reducing permeability at the point of pour before any surface product is even applied.
