There is no easy answer to this question, especially if the expectation is a long term solution vs. a temporary band-aid. There are so many different types of roof designs and roof surfaces that they must be evaluated individually. The age and condition of the roof is also a critical factor on whether the roof is a candidate for waterproofing. The most common types of roofs that my customers inquire about are asphalt based flat roofs, shingle roofs and cement tile roofs. Although all of these types of roofs can be waterproofed successfully, a lot has to be considered before and investment is made. My focus on this article will be the cement tile roof since they are the most rewarding yet the hardest to waterproof.
By far, the most frequently inquired about roof is the cement tile roof. Cement tile roofs are the most expensive roofs to replace due to the intense labor of removing the old tiles and the expense of purchasing new tiles and installing them. The unfortunate part is that the cement tiles are never the cause of a leaky tile roof; it is the underlayment beneath the tiles. Most homeowners agree that it is an unfortunate waste of resources and money simply because the underlayment (the least expensive component) of the roof has become brittle and is no longer waterproof. Often times the wood structure below is in perfect condition and the tiles are secure and perfectly functional. This leads many homeowners to believe that if they roll a coating over the tiles, it will solve the problem. Also, many roof coating suppliers, especially in the consumer market, often do not give the entire story on what is required to save a cement tile roof for the long term.
Acrylux has been manufacturing roof coatings since the early 1970’s and was one of the pioneers of waterproofing cement tile roofs. So, the answer to the question, will waterproof coatings same my cement tile roof is…maybe. The first evaluation for an aged cement tile roof with active leaks should be to have an inspection by a qualified person to determine if the structural part of the roof is in good shape. This means no rotted wood sheeting, no rusted away metal flashing, no missing tiles and nail on tiles should be secure. If the roof is in good shape, then a waterproof system can be considered. I also like to recommend having active leaks repaired prior to applying the waterproof system.
The biggest misconception about roof coatings is that the can simply be applied and all will be well. Unfortunately, there are steps to be taken prior to applying these coatings. Because all tile roofs are not seamless by nature; there are open seams above, below and on each side of every tile which have to be filled in prior to the coating being applied. Roof coating are not capable of bridging the gaps between all of the tiles, unless you were to do multiple coats--upwards of maybe four or five coats. Because this is not practical, the best approach is to grout the tiles like you would a floor or caulk each tile as needed. Although labor intensive, this approach gives a much more permanent seam which will last indefinitely as long as the roof is maintained with good quality coatings.
Once a seamless surface has been created, then a roof coating can do its job by creating a breathable covering over the entire roof area. Essentially the roof coating becomes the primary waterproofing by keeping moisture from ever reaching the deteriorated tar paper below. If you had all leaks fixed prior to coating the roof, the paper below is still functional and becomes the secondary waterproofing. This type of system has been applied to thousands of cement tile roofs over the years with many of them being maintained to well over 50 years; that s twice the original lifespan of the roof. So if your roof is a good candidate for a waterproof coating, YES, your roof can be saved.