Tom Parker, Owner, TCParker & Associates
It’s challenging to find something that brings homeowners more peace of mind than a sound roof over their heads. For hundreds of years, tile roofs have been considered the time-tested, ultimate roofing system.
A key concern with tile roofs is keeping the tile secure during wind events. Nothing illustrates this more clearly than the damage done by Hurricane Irma on Marco Island. Photo 1 (Click "Read more" to view in FRM) shows a mechanically fastened tile roof where tiles were lost in the wind event.
The damage is clear, as is the failure mode. Mechanical fasteners must be left a little “loose” or the tile will crack. In fact, inspectors will typically allow up to 1” of lift at the end of a mechanically fastened tile and still pass the job as meeting code. When the wind blows across the tile, it can lift the end of the tile, causing “chattering” to occur. As the chattering continues, the tiles are literally pried off of the roof, as seen in the ridge tiles hanging on at a 45 degree angle in the photo.
In photo 2 (next page), we see a nearby home with an adhered tile roof that was subjected to the same wind event and shows no damage. Adhesives lock the tiles in place, eliminating the potential chattering and subsequent failures.
Two types of polyurethane adhesives are available on the market. Both have similar chemistry with two main ingredients mixed together to form the polyurethane adhesive.
In “single component” adhesives, the two main ingredients are mixed in the tank at the factory to form a “pre-polymer.” This reacts with moisture once dispensed to create the final product. These products “rise” very little once dispensed and the adhesive typically will expand a further 5-10 percent as it fully cures over several hours.
In “two component” adhesives, the two main ingredients are taken to the job site in separate tanks and mixed together as they are dispensed. A chemical reaction takes place at that point to create the adhesive. The adhesive sprays out in more of a liquid state, then, as the reaction takes place, the adhesive “foams” and expands to three to four times its original volume, typically within a minute of spraying.
Single component adhesives are generally available in disposable tanks weighing less than 50 lbs. and these can be used on wet surfaces since they are moisture cured. Two component adhesives are available in small disposable tanks as well as large refillable tanks. The large sizes can provide economy of scale in some cases.
Manufacturers perform third party testing with their adhesive products in order to meet various code requirements. A Florida Product Approval can be obtained for inside and outside the High Velocity Hurricane Zone (HVHZ) based on the testing. The HVHZ is defined as Miami-Dade and Broward counties. Uplift values are listed in the Florida Product Approvals. Here is a link to the FPA search site: www.floridabuilding.org/pr/pr_app_srch.aspx
Miami-Dade County has additional requirements for both the adhesive product and the tile “system” in which is it used. Notice of acceptance (NOA) are required for both the product and then each of the tile manufacturer’s profiles (the system). To be used on a job in Miami-Dade County, the adhesive NOA needs to exist and the adhesive needs to be listed with uplift values in the tile NOA. In general, Broward County also utilizes the Miami-Dade NOAs and permitting
process. Here is a link to the MD search site: www.miamidade.gov/building/pc-search_app.asp
Manufacturers update their testing and approvals periodically, so it is recommended that approvals are pulled from these websites as needed rather than relying on printed copies you may have in your files.
Regardless of which type and brand of polyurethane foam adhesive you choose, the manufacturer’s installation instructions must be followed in order to comply with Florida Building Code product approvals and Miami-Dade NOAs.
Manufacturers are obligated by code to train and certify installers to ensure proper installation. From a safety standpoint, minimum personal protective equipment generally includes safety glasses, gloves and full covering clothing. Once polyurethane foam dries on a surface or skin, the only way to remove it is mechanically. So, a little preventative measure up front will pay off. Always consult the manufacturer safety data sheets for more details.
These products are all packaged in pressurized tanks. Avoid leaving the tanks in direct sunlight when not it use as the temperature can exceed the manufacturer’s recommended maximum storage temperature and possibly over-pressurized. Other product-specific procedures may be required, review the manufacturers installationinstructions for all the details.
Adhesives are more expensive than fasteners, however, in the total cost of a typical tile roof, the additional cost is in the 3-5 percent range. While use of adhesive adds a small percentage of cost to a tile roof installation, isn’t it worth the peace of mind that it provides to your customers?
Tom Parker, owner of TCParker & Associates, a technical sales agency representing TILEBOND roof tile adhesive. Tom grew up in the construction industry in his father’s residential construction company. He later earned a degree in Chemical Engineering and worked at Dow Chemical for 33 years prior to opening his agency in 2013. Tom is a Registered Professional Engineer.