At Roundtower Lime, we offer a carefully selected range of breathable sealants and hydrophobic agents designed to protect masonry surfaces from driving rain and moisture ingress while maintaining full vapour permeability. These products are ideal for heritage buildings, traditional stone and brick facades, lime-rendered surfaces, and porous natural materials where breathability is critical.
Our breathable sealants do not block moisture movement within the wall — they allow walls to "breathe" naturally while forming an invisible, water-repellent barrier on the surface.
Our Range of Breathable Sealants Includes:
Beeck SP Plus
A potassium silicate-based water repellent ideal for use on silicate mineral paints and renders. It penetrates deeply into porous surfaces and chemically bonds to the substrate, providing durable and long-lasting protection against rain and surface water.
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Water-based and completely vapour-permeable
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Non-film forming – zero risk of blistering or peeling
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Suitable for use over Beeck mineral paints and lime renders
Funcosil SL
A deep-penetrating, solvent-based water repellent designed for highly absorbent substrates. Excellent for historical masonry, sandstones, and lime mortars, where high diffusion openness and surface durability are critical.
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Solvent-based hydrophobic impregnation
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Colourless and UV-resistant
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Ideal for open-textured natural stone and renders
Funcosil SNL
A more universal, silane/siloxane-based hydrophobic treatment for mineral substrates with medium porosity. Funcosil SNL protects against frost damage, efflorescence, and organic growth, making it suitable for both conservation and modern projects.
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Invisible surface finish
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Provides resistance to weathering and moisture decay
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Breathable and non-glossy
Ideal Applications
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Lime-rendered façades
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Historic brickwork and stone masonry
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Unpainted mineral surfaces
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Silicate paint-coated elevations
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Breathable lime plasters and insulating plasters
These breathable sealants are ideal for exposed elevations, sea-facing properties, rural buildings, or any structure where moisture control must go hand-in-hand with breathability.
Frequently Asked Questions (FAQ)
Q: What does “breathable” mean in relation to sealants?
A: Breathable sealants allow water vapour to escape from within the wall while repelling liquid water from entering the surface. This prevents trapped moisture, which can cause damp, blistering, or decay.
Q: Can I apply these products over lime render or mineral paint?
A: Yes. Products like Beeck SP Plus and Funcosil SL are specifically designed for use over lime-based and mineral substrates. Always check compatibility or consult our technical team.
Q: Will breathable sealants change the appearance of the wall?
A: No. These sealants are invisible once cured, preserving the natural appearance and texture of the surface.
Q: How long does the protection last?
A: Typically 10–15 years, depending on exposure and surface preparation. Reapplication may be needed for particularly exposed elevations.
Q: Are these sealants suitable for listed or heritage buildings?
A: Yes. All products in this range are non-film-forming, reversible, and vapour permeable, making them appropriate for sensitive conservation projects.
