5 Ways to Extend the Life of Masonry Via Patching
Patching can be your friend, when done correctly
Patching of masonry materials during a new construction project is typically a line item that was not planned during the estimating phase of the project. Understanding the products commonly available for patching and their capabilities, compatibility, and limits will enable you to make better choices when selecting the products required for each patching condition.
Masonry restoration contractors typically are experts in the field of patching. A major portion of their business can come from repairing historic structures with deteriorating stone, concrete and terra cotta. The patching of stone on a building under construction may have several steps that are different from patching an existing masonry restoration project. This is due to color matching, stone preparation, pre-patch cleaning and moisture content of the substrate.
Though products have different characteristics and uses, the substrate in all cases must be free of loose and damaged material, greases, bituminous coatings, plant growth, paints and sealers. Proper preparation of the base material will ensure the best possible bond for the patching material. Following are five popular patching products seen in the field today.
Some products commonly used by stone masons have several different uses, depending on the repair or installation. Akemi has been used for years to secure anchors, set Dutchman pins and “glue” in patches. Mixing stone dust into Akemi can enhance the color of the epoxy, allowing for less obvious patch. (Just don’t overdo it.) Akemi for exterior use must be labeled as exterior-grade material and mixed with an activator to create the proper mix. Akemi can be sanded, polished and honed, offering many options for small patches. Akemi products with good ultra violet resistance are available on the market but are, by no means, the standard. When patching fine-grained granites and marbles, Akemi can be a great choice for repairs, with pre-planned color matching, short curing times and fine consistency.
Jahn Restoration Mortars are single-component restoration patching mortars mixed with water and applied drier than block mortar to create a durable, carvable and color-matched repair. This patching material can be used on a variety of substrates with predictable results. Competing with traditional patching materials that typically combine three materials – water, latex modifiers and base mixture – to create a patching material, this product eliminates the opportunity for mixing errors.
Latex modifiers are not simply the “milk” added to mortar. Latex modifiers offer many different compounds with many different properties to the mortars they enhance.
A few of the compounds commonly found and labeled as latex modifiers are carboxylated styrene butadiene latex emulsion and unique reactive acrylic additives. The bottom line is that latex modifiers improve mechanical performance, workability, resistance to the elements, and – most important – adhesion.
Latex modifiers are not for every patch application, but they do have a place in the market. Currently, the cultured stone industry has mandated that all mortars shall be, as a minimum, latex modified – a plus for the applicators in this industry.
Typically, masonry mortar is not a good choice for patching many types of masonry. Sure, it will hold for a short time, but as a long-term patching material, the properties of mortar will not perform well. The addition of latex modifiers will help it to “stick” to the substrate, but it is recommended that, if you are considering using masonry mortar as a patch, you not use it for a structural patch or a decorative patch. The labor will not be worth the long-term results.
Concrete patching can be as simple as rubbing slurry over pock holes or parging concrete into a large chip. This type of patching is not the intent of this article, as the focus is on products formulated for specific concrete repairs. These patching mortars can be used on precast, some cast stone products and many terra cottas available to the industry. With the ability to handle above- and below-grade applications, these products allow for many opportunities for a quick repair when least expected. Patching mortars can be water permeable, and it is suggested that the product manufacturer be contacted after curing for recommendations on whether to use a water repellant.
Not every chip should be patched. Many patches, no matter how well they are installed, will draw the eye to the patch and not to the overall appearance of the elevation. Many chips are too shallow and feathered, which will cause many patching compounds not to perform as well. A shallow patch should only be applied in mandatory situations. However, they must be cut at the perimeter of the patch to create an edge, along with increasing the depth of the patch to meet the minimum depth requirement for the material that you choose.