Concrete Blocks and Water Permeability: What You Need to Know

Concrete Blocks and Water Permeability: What You Need to Know

For anybody looking to begin a construction project, knowing how water permeable your material is can make all the difference on how long your structure will last for, so you have to get it right the first time.

In this blog, we will discuss concrete blocks and water permeability: What you need to know

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.

How does water affect concrete?

How does water affect concrete?

Surprisingly, water can affect concrete in both positive and negative ways:

Positive effects

  • Hydration: Water is essential for the curing process of concrete. It allows the cement to hydrate and form the strong calcium-silicate hydrate (C-S-H) gel that binds the aggregate particles together, giving concrete its strength.

Negative effects

  • Freeze-thaw cycles: When water in concrete freezes, it expands in volume. This repeated freezing and thawing can cause cracks and deterioration in concrete, especially if it’s saturated with water.
  • Corrosion of steel reinforcements: Water can cause steel reinforcement rods within concrete to corrode, which can lead to cracking, spalling (flaking), and loss of structural integrity.
  • Efflorescence: When water carrying dissolved salts migrates through concrete and evaporates on the surface, it can leave behind white deposits, known as efflorescence, which is unsightly but not necessarily harmful structurally.

Can you make concrete fully waterproof?

No. Concrete can not be made 100% waterproof. However, there are strategies available to help you significantly reduce water permeability in concrete:

  1. Selecting the Right Mix: A denser concrete mix with a lower water-to-cement ratio will have fewer pores for water to seep through. Specific admixtures can also be incorporated during production to enhance water repellence.
  2. Waterproofing Membranes: Liquid-applied or sheet membranes can be applied to the concrete surface to form a flexible, waterproof barrier.
  3. Proper Curing: Ensuring adequate moisture during curing allows for complete hydration and minimizes cracking, which can be entry points for water.
  4. Surface Treatments: Penetrating sealers or topical coatings can be applied to the concrete surface to repel water. These are most effective on sound, clean concrete.

Even with these methods, concrete will still have some level of permeability, especially under constant water pressure. The best approach depends on the specific application, budget, and desired level of water resistance. Waterproofing membranes and sealers may require periodic reapplication for optimal effectiveness.

For structures in constant contact with water, a denser concrete mix should be combined with a high-quality membrane or coating for maximum defence. Addressing existing cracks with a suitable sealant before applying waterproofing treatments is also crucial.

By understanding water’s role and implementing these strategies, you can significantly enhance concrete’s water resistance and ensure the longevity of concrete structures.

Concrete blocks and water permeability: What you need to know

Concrete blocks and water permeability: What you need to know

Concrete blocks, while generally known for their strength and durability, aren’t entirely waterproof. They have varying degrees of permeability depending on several factors. Here’s a breakdown of what you need to know:

Porosity: Concrete blocks contain tiny air pockets and voids throughout their structure, which is known as porosity. This porosity allows some water to seep through, especially under pressure or continuous exposure.

Types of Blocks

  • Solid Concrete Blocks: Denser and less porous than their hollow counterparts, they offer better water resistance.
  • Hollow Concrete Blocks: These have cores or voids running through them, making them lighter but also more susceptible to water penetration.

Other Factors Affecting Permeability

  • Mortar Mix: The mortar used to bind the blocks can also influence water resistance. Denser mortar mixes with water repelling additives can reduce water permeation.
  • Sealing: Applying a water-repellent sealer to the exterior of the block surface can further enhance water resistance.
  • Installation: Proper installation techniques, like filling hollow cores with grout or insulation, can significantly reduce water pathways within the block wall.

Concrete blocks and water permeability: The takeaway points

Standard concrete blocks have some level of water permeability. That being said, solid blocks offer better water resistance than hollow ones. Furthermore, the type of mortar mix, sealing, and installation techniques all play a role.

So what does this mean for you? Well, a few things. Firstly, understanding permeability is crucial for choosing the right concrete block type for your project. So, for projects exposed to high moisture, consider solid blocks, denser mortar mixes, and waterproofing sealers.

Once again, proper installation techniques are essential to prevent water from entering and causing structural issues. Regardless if you have the right block, if it is installed poorly, it won’t be as effective as you thought.

Can moisture be removed from concrete?

Can moisture be removed from concrete?

Yes. Here are some methods for removing moisture from concrete:

  1. Natural Drying:

Air Circulation: Opening windows, using fans, and promoting ventilation. Aim for warm, dry air for faster drying.

Dehumidification: consider using a dehumidifier to remove moisture from the air. This can be particularly effective in humid environments.

       2. Drying Acceleration Techniques:

Heat Lamps or Desiccants: These methods directly apply heat to the concrete surface to drive out moisture. Heat lamps radiate heat, while desiccant dehumidifiers use a desiccant material that absorbs moisture from the air.

        3. Specialised Techniques:

Forced Air Drying: This involves using specialised equipment that forces warm, dry air through channels placed under the concrete slab. This is a powerful method but requires professional expertise.

Chemical Drying: In extreme cases, chemical treatments can be used to absorb moisture from the concrete. This should only be done by a professional due to the potential hazards of the chemicals involved.

Are Interlocking Concrete Blocks water permeable?

Yes. As they are made from concrete, Interlocking Concrete blocks have a degree of water permeability, though this can be made more waterproof if required.

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

Invest in 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 aptly explained concrete blocks and their water permeability, including everything you need to know.  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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