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Silane / Siloxane Water Repellents

High Performance Silane / Siloxane Water Repellents

One month ago, I walked into a national chain discount store. Coming out of the exit door was a woman with a 5 gallon can of a highly advertised masonry sealer in her shopping cart. My gut instinct told me that she was probably buying it to spray on her brick walls or concrete driveway. I just didn't get the feeling that she worked at a testing laboratory. Anyway, what a shame. The product she purchased was stearate-based. That means the main component of the product is very likely animal fat. These products and silicone based sealers are actually film forming sealants. They are just about the worst thing you could ever put on your brick or masonry surfaces - especially if you live in a climate that experiences freezing temperatures.

Film forming sealants do just that - they form a film on the surface of your masonry. It is a clear film that can sometimes turn cloudy. The film can also block water vapor from escaping to the atmosphere. If water vapor works its way to the surface of masonry, collects and then freezes, you can suffer spalling, flaking and other surface deterioration.

The better way to treat masonry is to apply penetrating water repellents. These products contain special chemicals called silanes and siloxanes and/or a blend of the two chemicals. These nifty chemicals partially block the capillaries in brick, concrete and mortar. The partially blocked spaces then actually repel water instead of allowing it to enter the masonry. Since the passageways are not entirely blocked, they allow water vapor to readily escape to the atmosphere.

I have listed a few companies that make high performance silane and/or siloxane water repellents. There are undoubtedly twice as many as I have listed ... maybe more. Many if not all of these products are sold exclusively at brickyards or specialty building supply stores that sell to bricklayers or concrete contractors. You can find these stores by looking in your Yellow Pages. Look under "Building Supplies" or "Brick." One of the companies below not only sells to these specialty stores but also sells directly to homeowners. They ship the product directly to your front door via UPS. Call Saver Systems listed below and see real customer service in action! Ask for Masonry Saver.

Act Quickly

Many of the brick and masonry sealers have to be applied in favorable weather conditions. Most are temperature sensitive. That means the air and surface temperature must not be below a certain minimum temperature. Read the instructions carefully!

  • Sivento Silanes
  • ProSoCo, Inc.
  • Saver Systems

Further Reading

  • Measuring Water Penetration
    by Kim Basham & John Meredith
    Masonry Construction November 1995
    (This article is available in PDF format for free downloading from the Masonry Construction web site!)

  • Reducing Water Permeance in Masonry Walls and Chimneys
    John Meredith
    Sweeping April / May 1994


23 Responses to Silane / Siloxane Water Repellents

  1. In looking for a way to reduce/prevent mold on our brick home surfaces, I've been directed to Siloxane PD water repelent. Any product information does not mention this product for this purpose- IS this the type of product to use for mold protection, and if not,what should I be looking for to spray on to the brick?

    Any info would be most appreciated.

  2. We sprayed our new stone chimney with Siloxane and later that day it rained (not in forcast) . It ran down on our shingles and we now have a white stain around our chimney. Is there a product to remove the sealer stain?

  3. I have stone wall that has been sealed with hydrozo double 7 and left it a different shade than the rest of the home. is there any way to remove the sealer from this surface?

  4. I have a farm house built in 1829 with bricks made from clay dug onsite. My family bought house 40 years ago and walls were covered with stucco. Some stucco has been removed to reveal original brick; some brick is deteriorating. What can I do to restore and maintain it? Will a silane/siloxane water repellant do the trick? Can I fix the damage already done?

  5. Hi, my contractor recommends prosoco Siloxane WB for an indoor travertine floor.

    My purpose is to add shine and get the scratches to disappear. Wiping down with water does this so I know that can happen, but obviously water is not the solution.

    Do you think the Siloxane is a good solution? Something else?


  6. A contractor applied a concrete sealer rather than a waterproofer on a brick chimney. I think this is the wrong product and wonder if I can have this sealer removed from the surface of the brick. The product's technical hotline says that the product allows for block and concrete to breathe, seems hard to believe a sealant allows breathing. Please send advice...

  7. After grinding and cleaning my concrete floor I have sealed it with 2 coats of silane. I was wondering if I can add an epoxy or polyurethane coating over this?

  8. Can the silane/siloxane mix you refer to be used as an alternative to parging? I live in Canada where we experience freeze/thaw cycles.

  9. Can masonary walls on a high rise be treated with waterproofing silane/siloxane and then be painted over with the usual primer/ undercoat/final overcoat?

  10. I'm really confused. Please explain further how this product "partially blocks water" but lets it escape. I don't want any water in at all. I'm a logical person and am not understanding how something is supposed to block water from coming in, but then lets it out if the water does come in? (Or vapors) To me, it's like a baggie. I don't want anything coming into the baggie. You are saying there is a baggie that will keep the water partially out, but if it does come in, it will let it evaporate out. I'd rather just get a baggie that keeps the water out altogether. (I do understand about the dangers of water getting in, and not getting out.) I'm sure there is a simple explanation for this, and am waiting patiently for an answer. I'm trying to find a sealant for my chimney bricks that are leaking a little. I'm looking at Loxon® 40% Silane Water Repellant, OR Lifetime (Registered Trademark)
    WATERPROOFING SEALANT (from Coatings International - the 6% sealant) I don't know which one to get. Thanks for your website!! It's very informative! Teri

  11. As a chemist I have worked a lot with silanes, siloxanes and silicones to coat mineral and glass materials. The first 2 are usually used as water repelling coatings to provide an extremely thin layer only 1 or 2 molecules thick. So in the pores of things like brick and concrete they react with the material to coat the passageways but leave a central passageway in each pore unblocked. Water vapor, being a quite small molecule, can easily pass out through the pores but liquid water like rain is repelled quite effectively. So water in the inside of concrete can vaporize and pass to the outside but rain from the outside has trouble getting in since the pores are now hydrophobic ( hate water). Silicones and oil types of sealers do not act this way and may block vapor transmission until they wear off.

  12. Hi. I want a white brick veneer backsplash in my new kitchen. I found one I love, but I am worried that its going to end up looking like crap after a while if it gets splattered with grease and whatever when Im cooking. I have a sealed and unsealed brick (Im not sure exactly what its sealed with - the company I got the sample from sealed it) and I have put some oil on it, coffee on it, juice on it and the sealed one is holding up well, but is a little stain on it from the oil. Can you tell me the best product you know of that repells oil as well as water?


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