Masonry Treatments: Inside Silane/Siloxane Technology

Water is one of the most persistent forces acting on masonry. It moves through capillaries and seeps into micro-cracks. Over time, this moisture can trigger efflorescence, spalling, and structural decay, although mould growth typically occurs on damp internal finishes rather than the masonry itself.

Hydrophobic masonry treatments, especially those based on silanes and siloxanes, repel liquid water while preserving vapour permeability, allowing buildings to breathe. Unlike film-forming coatings that can crack, peel, or trap moisture, these penetrating treatments integrate within the capillary structure.

Understanding the capillary structure of masonry

Concrete, brick, and stone contain networks of microscopic pores where water enters via capillary action and travels considerable distances. Traditional surface coatings form films that may fail over time, whereas silanes and siloxanes can penetrate deeply and react internally.

Water is one of the most persistent forces acting on masonry. It moves through pores, upward through capillaries, and seeps into micro‑cracks. Over time, this moisture can trigger efflorescence, spalling, mould, and structural decay. Hydrophobic masonry treatments, especially those based on silanes and siloxanes, offer a powerful way to stop liquid water while still allowing buildings to breathe. But how do they actually work?

What makes silanes and siloxanes different?

Both silanes and siloxanes belong to the silicone family, but they behave differently once applied.

• Silanes are small molecules. Their low molecular weight allows them to penetrate deeply into dense materials like concrete.
• Siloxanes are larger molecules. They don’t penetrate as far, but they work well on more permeable substrates such as brick or sandstone.

Together, they create a hydrophobic network inside the material—one that repels liquid water without forming a visible film.

The chemistry behind hydrophobicity

When a silane or siloxane treatment is applied, the molecules migrate into the pores. Once inside, they react with the minerals in the substrate. This reaction forms a durable chemical bond. The result is a microscopic layer of water‑repellent groups attached to the pore walls.

These groups don’t block the pores. Instead, they change the surface energy of the material. Water droplets can no longer wet the surface, so they bead and roll off. Vapour, however, can still move freely.

This is the key advantage: liquid water stays out, but moisture inside the wall can still escape.

Why hydrophobic ≠ sealed

A common misconception is that hydrophobic treatments “seal” masonry. In reality, they do the opposite. They avoid sealing. They maintain vapour permeability, which helps prevent trapped moisture, blistering, and long‑term deterioration.

This breathable protection makes silane and siloxane systems ideal for:

• heritage masonry
• concrete facades
• permeable brickwork
• retaining walls
• coastal environments

They protect without changing the appearance or interfering with the building’s natural drying cycle.

How long do these treatments last?

Because silanes and siloxanes bond chemically within the substrate, they offer long‑term durability. Their lifespan depends on exposure conditions, substrate density, and application quality, but high‑quality formulations can protect masonry for many years with minimal maintenance. When the silane is bonded to the masonry it is virtually impossible to break this bond which makes it permanent.

Unlike surface films, they don’t peel or crack. They simply continue working inside the material.

Why this science matters for real‑world performance

Hydrophobic masonry treatments aren’t just a product category, they’re a moisture‑management strategy. By understanding how silanes and siloxanes work, builders and homeowners can make smarter choices about waterproofing.

They offer:

• deep penetration
• invisible protection
• long‑term durability
• vapour permeability
• resistance to efflorescence and freeze‑thaw damage

In short, they protect the building while respecting the material.

Silanes and siloxanes transform masonry from the inside out. They create a hydrophobic network that repels liquid water, preserves appearance, and supports healthy drying. For anyone seeking reliable, breathable, long‑lasting protection, this technology offers a proven and scientifically sound solution.

To learn more about how Tech-Dry solutions can protect your property, visit our product page.