We live in an apartment style condominium building. I am on the Board of this condominium. One of the questions that we get, and that we wrestle with, is what should be permissible as a coating on the floor of the hollow core concrete balconies. In earlier years some unit owners had carpeting glued to the surface. We know that this is not a good practice and we discourage it. However, we are now getting requests from owners who are in the process of removing the carpeting and who wish to paint the floor of their balcony with some of the new concrete paints/stains that have appeared on the market. Would painting/staining be recommended or would it become unsightly with flaking? Even worse, could it lead to deterioration of the surface of the balcony? Our interests, as a Board, are on the longevity of our exterior surfaces, and on their overall appearance. As an additional query, are there any other products/surfaces on the market that would be recommended? We are located in Winnipeg , so our winters are severe.
One of the first things I tell homeowners during the initial, exterior part of my inspections is to remove any carpeting from steps or patios. You are correct that the carpets are a bad idea as they may remain damp for a long period of time after wetting from rain and snow. If concrete stays wet, particularly when outside temperatures fluctuate between freezing and thawing, it can cause premature deterioration as the moisture and ice seep into cracks or openings in the surface of the concrete. I am glad to see that you discourage this practice for your balconies, but it may be somewhat less of an issue in your case, as the balconies may be protected from a great deal of precipitation by the floor above.
Despite the partial covering of the balconies in your condos, removal of the carpet and the adhesive will be a considerable improvement for the longevity of the concrete. Removal of the adhesive may be the most difficult part of the process, as it may require considerable scraping or use of chemical strippers or solvents to get back to the bare concrete. This will be critical to ensure proper adhesion of the new finish on the concrete. Care should be taken to ensure adequate ventilation and breathing protection during this process, to avoid inhaling toxic fumes.
I have not personally seen stain successfully applied to exterior concrete surfaces, but there are new products on the market all the time, and one may be available. I would ensure that you get proper advice on use of these products from the manufacturer or knowledgeable retailer before trying them. The results could be awful looking, and difficult to reverse, once applied. For that reason I will stick to discussions of paint and similar surface coverings.
Painting an older concrete exterior surface should not cause any negative effects as long as the proper material and preparation methods are used. Painting this type of surface may actually help protect the surface from damage due to excess moisture and mechanical wear. Painting the balconies may also allow for caulking, sealing, or patching any cracks or worn sections which may further prevent moisture & ice damage. Concrete patches may be unsightly, but when painted may blend in to be much less noticeable and a considerable cosmetic improvement. Painting, by its very nature, may also enhance the aesthetic value of the balcony surface.
As previously stated, proper surface preparation is essential for proper adhesion and durability of the painted surface. Once the old carpet adhesives are completely removed, the surface will likely require a primer to ensure that the finish coating will adhere. Check with the paint supplier to get the proper primer for the job and allow adequate time for drying prior to topcoat application.
You will have several options for surface finishes, which may be partially dictated by your intended use. There are many easy to apply latex-based concrete paints designed for moderate wear. This will be the easiest to use, but may not be durable enough to withstand constant human traffic. If you use your balcony very regularly, as well as sliding patio furniture and other items on the surface, more durable alkyd, epoxy or polyurethane based paints may withstand this better. These may also be more susceptible to peeling, as you have wondered about, but will provide a much harder surface finish. Again, check with the paint suppliers for information of the various products available.
Finally, there are several relatively new products on the market that may be an even better choice than traditional paint. Many of these produce an imitation stone or masonry finish to further enhance the look of the balcony. While this is a desirable end result, it may not be the only advantage. Most of these imitation masonry finishes have a rough-textured component, which gives the product its desired effect. I like this feature as it serves two purposes, in my view. First, it provides a measure of slip resistance, which can be a problem with glossy painted surfaces. Secondly, it helps hides minor imperfections in the concrete by diffusing the way light hits the surface, further enhancing the look. The durability of these products in our climate may not be known for several years, but again the partial covering of your balconies may help considerably to reduce moisture and sun exposure.
Whichever finish you choose, it should be a vast improvement over the older, moisture trapping carpets currently installed. The new finish will help prevent further moisture absorption, which can only enhance the longevity of the concrete balconies.
