Do Concrete Blocks Let Water Through

Do Concrete Blocks Let Water Through?

Concrete is known for having a list of qualities that make it a superior construction material. However, when it comes to water, is it still secure? Even though it has a naturally porous surface?

In this blog, we will answer the question ‘Do concrete blocks let water through?’

At PPC Concrete Products, we are here to provide solutions for your construction needs,

from the person working their own part-time project, to commercial clients, and everyone in-between.

Monthly construction output had risen an estimated 1.6% value in June 2023, and we would like to think our accessible concrete products had a small part to play by giving our clients easy access to reliable and easy-to-use construction solutions.

Which grade of concrete is the most waterproof?

Which grade of concrete is the most waterproof?

While density and high-quality block selection are important, forget about “grades” for water resistance. The real key is applying a sealant to the concrete block surface. This significantly reduces water penetration, regardless of the block’s base permeability. Different sealants exist for various applications.

Another crucial factor is hydrostatic pressure, the amount of water pushing against the blocks. Even well-sealed blocks can struggle under high pressure. For foundations and retaining walls, proper drainage and reduced pressure are essential for waterproofing.

To maximize water resistance:

  • Choose denser, high-quality concrete blocks.
  • Apply a high-quality sealant suited to your specific use case.
  • Address hydrostatic pressure by improving drainage around the concrete block structure.

Where should concrete not be used?

Concrete is a workhorse material in construction, but it does have some Achilles’ heels. Here’s where concrete might not be the ideal choice:

Chemical Battles

Highly acidic or alkaline environments can cause concrete to deteriorate. Seawater and harsh chemicals are culprits here. In such cases, acid-resistant concrete mixes, special alkali-resistant blends, or even alternative materials like fibreglass or brick might be a better fit.

Freeze and Thaw Foes

Standard concrete can struggle in areas with frequent freeze-thaw cycles. The water inside the concrete expands when it freezes, creating cracks and weakening the material. Air-entrained concrete with tiny air pockets to accommodate the ice or specially formulated freeze-thaw resistant mixes can be solutions here.

Flexibility Matters

Concrete is rigid and doesn’t handle significant movement or vibrations well. Earthquake zones or structures needing to flex might require steel or other more flexible materials.

Looks Aren’t Everything

While modern concrete can have a certain charm, some architectural styles might call for a different aesthetic. Brick, stone, or wood offer unique visual possibilities.

Budget vs. Performance

Sometimes, superior performance outweighs cost concerns. Laboratories or clean rooms might benefit from epoxy floors instead of concrete due to their superior chemical resistance and seamless surfaces.

It’s important to remember that these are general limitations. Advanced concrete formulations and smart design techniques can often overcome these challenges. Consulting with a structural engineer or concrete specialist is always recommended to determine the best material for your specific project and environment.

Do concrete blocks let water through?

Do concrete blocks let water through?

Concrete blocks themselves are somewhat permeable, meaning they can let some water through. This is due to the structural nature of concrete itself, let us explain:

It has a porous nature

Concrete blocks, like most concrete, have tiny pores and voids throughout their structure. These gaps allow water to seep through, especially under pressure or continuous exposure.

More permeable than poured concrete

Concrete blocks tend to be more porous than poured concrete due to their manufacturing process. Poured concrete can be more tightly compacted, leading to fewer voids.

Mortar joints

The mortar joints between concrete blocks are another point of water ingress. Over time, these joints can crack or deteriorate, allowing more water to penetrate.

However, there are several factors that influence how much water gets through concrete blocks:

  • Quality of the blocks: High-quality blocks made with denser concrete mixes will have less water permeability.
  • Sealing: Applying a sealant to the surface of the concrete blocks can significantly improve their water resistance.
  • Hydrostatic pressure: The higher the water pressure pushing against the blocks, the more likely water is to seep through.

Signs concrete blocks have let water through

  • Cracks: Cracks in the concrete, especially hairline cracks, can be a sign that water has penetrated and caused the concrete to expand and contract.
  • Spalling: If the concrete surface starts to flake or crumble, it could be a sign of water damage that has caused the material to deteriorate.
  • Efflorescence: This is a white, powdery substance that can appear on the surface of concrete. It’s caused by minerals left behind as water evaporates and can indicate water movement through the concrete.
  • Discolouration: Water stains or darker patches on the concrete can be a sign of moisture absorption.
  • Mould or mildew growth: Mould and mildew thrive in damp environments. Their presence on or near concrete surfaces suggests water infiltration.

What are the most efficient concrete blocks?

What are the most efficient concrete blocks?

Interlocking Concrete Blocks are a variation on the traditional concrete block, and can be argued are the most efficient kind of concrete block. These special pre-cast blocks do not require mortar in order to create a long-lasting and effective connection, and are available in multiple sizes.

Interlocking Concrete Blocks connect to each other via studs and recesses at the top and bottom of the blocks, respectively. Individually, concrete blocks are heavy, but once they are joined, they provide an excellent counterweight against exceedingly heavy applications like a retaining wall.

Considering the fact they do not require mortar to connect, it is safe to say you will be saving money that would otherwise be spent on binding materials, and even some labour costs. But what actually makes Interlocking Concrete Blocks special? Well, a lot of things.

Here is a list of some of the uses that Interlocking Concrete Blocks can facilitate.

  • Material Storage bays
  • Blast walls
  • Salt stores
  • Crash protection
  • Push walls
  • Security barriers
  • Segregation bays, i.e. recycling centres
  • Retaining walls
  • Industrial buildings
  • Fire breaks
  • Counterweights
  • Roadblocks

Do Interlocking Concrete blocks let water through?

Interlocking Concrete Blocks are weather resistant, but not waterproof. If subjected directly to continuous moisture, eventually it may get through. However, this can be rectified by applying a waterproof coating over the concrete once the structure is set.

What can you use to waterproof concrete?

There is more than one option available when it comes to waterproofing concrete. Here are the kinds of options you can explore:

  • Cementitious waterproofing: A coating mixed with cement creates a thin, breathable barrier applied directly to the concrete surface.
  • Liquid waterproofing membranes: These are thin, sprayed or rolled-on coatings that form a flexible, waterproof layer. They come in polyurethane or acrylic variations.
  • Bituminous coatings: Asphalt-based coatings offer strong waterproofing, but are less flexible and can’t handle sunlight exposure. Best suited for foundations.
  • Bituminous membranes: Similar to coatings, but thicker and more permanent. Ideal for flat roofs exposed to weather elements.
  • Crystalline admixtures: Mixed directly into the concrete during pouring, these special ingredients react with water to form microscopic crystals that fill pores and enhance waterproofing from within.

Find the best concrete blocks today

As an established supplier all over the UK, PPC Concrete Products is always happy to help, which is why we encourage you to get in touch with any questions you may have or have a look at our FAQ.

In this blog, we hope to have answered the question “Do concrete blocks let water through?” Whilst also providing additional information including construction solutions that we offer.

Take a read of our case studies to truly understand how we have provided solutions for business in the past with the use of our interlocking concrete blocks, and ultimately, how we can help you today.

Read our blog page for more insights into our passion, construction.


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Higginshaw Lane,




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Monday to Friday – 8 AM until 4 PM

Tel: 01706 655245


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