With today's breathable sealers and water repellents, sealing masonry can be a powerful tool for protecting and preserving your masonry investment. When water enters masonry and is able to escape there usually isn't a problem. When water enters masonry and cannot escape, it then undergoes freeze/thaw cycles (contraction/expansion) which lead to the deterioration of masonry over time. The proper water repellent or sealer can prevent this unwanted water from entering your masonry while still allowing any moisture that's present in the masonry to escape. As an added benefit they can also prevent stains (like a wine spill) and make masonry cleaning quicker and easier
In most cases when we are trying to prevent water entry into brick, block or mortar we recommend using a silane/siloxane water repellent. This product is designed to penetrate the surface of the brick, block or mortar and over the course of several days it undergoes a chemical process with the substrate to form a water repellent barrier. By penetrating and not sitting on the surface it does not change the appearance of the brick, block or mortar so it is essentially invisible. It is important to remember that the water repellent will have to be periodically reapplied and the length of time between applications depends on the material and conditions to which it is exposed.
When we are trying to prevent water entry into stone (most commonly bluestone patios) we generally recommend using a penetrating sealer that contains polymers instead of a silane/siloxane water repellent. This is because the polymers have very small molecules and they carry or allow the sealer to penetrate the very dense stone. The silane/siloxane water repellent has larger molecules which prevents it from penetrating the stone very well. As with the water repellent mentioned above, the sealer also penetrates so it does not change the appearance of the stone and is essentially invisible. This product will also have to be reapplied ocassionally; however, it lasts substantially longer than the silane/siloxane water repellent.
Both of the products mentioned also contain a base that allows it to be in liquid form and travel into the masonry. Both type of product are available as a water-based product or a solvent-based product. Solvent-based products tend to allow the product to penetrate deeper into the masonry and the can be applied in colder temperatures because they have a lower freezing point than water. Water-based products do not have the odor that the solvent-based products have, are less harmful and usually clean up with just soap and water so these products are ideal for use indoors.
Please contact us (firstname.lastname@example.org) if you feel your masonry could benefit from a sealer or water repellent and we will be happy to discuss what product(s) work best for you and your situation. Also, please contact us if we can answer any questions you may have on sealers or water repellents.