A Weak Link in Florida’s Roofing Underlayment Requirements

Sun, Oct 01, 2023 at 3:25PM

Mike Silvers, CPRC, Owner, Silvers Systems Inc. and FRSA Director of Technical Services

The Issue

The Florida Roofing and Sheet Metal Contractors Association (FRSA) has been at the forefront in making the Florida Building Code’s (FBC) roofing requirements stronger than any other building code in the country and, quite possibly, the world. The effort is warranted due to Florida’s unique geographical exposure to hurricanes and the need for roof systems that will minimize potential property damage when they occur. The roofing industry and other stakeholders have been instrumental in these efforts. During the development of the 8th Edition (2023) FBC, the industry worked together to improve underlayment performance and, in particular, to bring the more stringent requirements used in 65 of Florida’s 67 counties into the High Velocity Hurricane Zone (HVHZ) sections of the FBC. The HVHZ is comprised of Miami-Dade and Broward Counties only. This area has the potential for the highest wind speeds in Florida based on the ASCE (American Society of Civil Engineers) wind speed maps shown below.

ASCE 7-22 Wind Map for Florida

For over two years, we proposed and advanced several modifications to the code that would strengthen and standardize roof underlayments for all types of steep-slope roof systems in the HVHZ (a steep-slope roof system is one that has a pitch or slope equal to or greater than 2 units vertical to 12 units horizontal.) This effort was preceded by many attempts of people in the industry to work with Miami-Dade County to find a reasonable solution to its lagging underlayment requirements. We felt these changes were needed not only to achieve better performance of many types of roof coverings but also to greatly improve the underlayments’ ability to serve as secondary water barriers (SWB), which are required in the code. SWBs have proven to be very effective at preventing both extensive interior damage and the displacement of the building’s occupants in the event of a roof covering failure. Miami-Dade County pushed back against these changes at every opportunity, even after the outcome became clear. Most of the changes were ultimately accepted but, despite our efforts and the Commission’s well-informed decisions, a weak link in these code changes still inexplicably remains: Miami-Dade County’s reluctance to comply with the Code changes.

What Did the Florida Building Commission Decide?

The underlayment changes were approved over the course of three Technical Advisory Committee (TAC) meetings (for which a 67 percent vote is required) for a positive recommendation to the Commission. We opposed many attempts by Miami-Dade County to amend the modifications in ways that would have weakened their effectiveness. These amendments are referred to as comments: we will refer back to a particular comment below that is very important in understanding our concerns. During four Florida Building Commission meetings (for which a 75 percent vote is required for approval), the changes were accepted and incorporated into the code that will go into effect on December 31.

The comment I want to address was submitted by Miami-Dade County. It contained two major amendments that would have eliminated some of the most important changes that had been approved by the Commission. First, if accepted, the comment would have required a nailable underlayment over the roof sheathing, thereby eliminating the availability of self-adhered underlayment (sometimes referred to as “peel and stick”) installed directly to the deck. (The “deck” is referred to in the code as sawn lumber, wood plank or wood structural panel deck.) Self-adhered underlayment has been widely accepted by the roofing industry in almost all of Florida for well over a decade. It has also been embraced by the property insurance industry, which offers its largest credits for this type of secondary water barrier. Self-ahered underlayment applied directly to the deck has proven to be very effective and offers very high uplift resistance values. (Uplift is the force that tries to suck the roof off of a structure during a high wind event.) This amendment, proposed by Miami-Dade County officials in an attempt to undo what the Commission had already approved, was denied. However, the second part of the comment was also very important. It requested a reduction in the tested uplift pressures to -90 psf ultimate. (The FBC and the model codes require a safety factor of two to account for potential minor material and installation variations or deficiencies, among other things. So, an underlayment that attains a -90 psf ultimate in testing is halved to -45 psf.) This request was also denied. That should have resolved the issue but, unfortunately, it has not.

Miami-Dade Checklist 90 for the Approval of Roofing Under

The Weak Link: Tile Roof Underlament Uplift Resistance in the HVHZ

Many of these important underlayment changes have finally been accepted as inevitable by Miami-Dade County and appear to be moving toward implementation, which would seem reasonable based on the decisions made by the Commission. These improvements will unquestionably lead to better secondary water barriers for almost all steep-slope roofs. This was no small accomplishment. These changes will provide huge dividends for insurers and the insured when a major hurricane occurs in the HVHZ counties, at least for roofs permitted under the new code. It will also offer its residents the same level of protection already available to Florida citizens who live outside of the HVHZ. However, there is still a weak link in the underlayments used for the predominant steep-slope roof system in this area, tile roofs. A recent survey of industry professionals estimated that between 50 to 60 percent of steep-slope roofs in the HVHZ are tile. Tile roof systems, as well as low-slope roof systems (those with a pitch or slope below 2 units vertical and 12 units horizontal), are not required to comply with the code’s secondary water barrier provisions: primarily because they have historically been assumed to meet or exceed code-required uplift resistance levels. A system, however, is only as strong as its weakest link. So, if the tile underlayment is not tested to meet ASCE 7 uplift resistance values – as mandated by the Code – the ability of the entire sytem to resist high winds is greatly undermined. Miami-Dade County, instead of complying with the Florida Building Commission’s direction regarding underlayment uplift resistance, has issued “ Checklist #0090 For the Approval of Roofing Underlayment” to give guidance to the roofing industry on how it intends to implement these code changes – or perhaps one should say how it intends to avoid implementing these code changes. Note 3 (outlined in red at the bottom of the document) states:

Uplift Testing submitted to support an Underlayment Uplift Design Pressure will accept 1 specimen achieving a minimum -45 psf. (after applying 2:1 safety factor).

Miami-Dade County has indicated that any tile underlayment that meets this negative pressure will be issued a Miami-Dade County Notice of Acceptance (NOA). Also, it has indicated that uplift pressures will not be listed in the NOA. We feel that this is a major divergence from the intent of the changes adopted by the Commission and included in the new code. The ASCE 7-22 uplift resistance pressures for tile roofs located in the HVHZ will very seldom, if ever, be this low. Pressures two or three times this high are far more common in the HVHZ. The calculations in the Standard Building Advisors report below show a pressure of -108.1 psf (circled in red) for a house in the HVHZ, which does not, by any means, represent the highest uplift values in the zone.

The acceptance of -45 psf as the maximum required resistance would definitely result in a severe weakening of the new code. In particular, how it deals with tile underlayment and its ability to serve as part of an overall wind resistance roof system and serve as an effective secondary water barrier that meets the pressures derived from ASCE 7-22.

Standard Building Advisors Wind Uplift Calculation for Miami-Dade Property

Why We Should Be Concerned

As I mentioned previously, a large percentage of steep-slope roofs in the HVHZ are tile. In many other areas of Florida, tile is also a prominent roof system. Unlike an NOA issued by Miami-Dade County, a Product Approval issued by the state of Florida includes the maximum uplift pressure that an underlayment system has resisted through verified testing. With that information someone designing a tile roof system can use that listed pressure to make sure that it meets or exceeds the pressures from ASCE 7. Remember, according to Miami-Dade County, its notices of acceptance will not list even the very low -45 psf uplift resistance, leaving those that depend on that information without critical data. To further understand the concerns of designers, please see the boxed text below with a question from a registered Engineer, Kelsey McMenamy, and the answer from Miami-Dade County that was posted on the Roofing Contractors Association of South Florida (RCASF) website. The post is a few years old but it shows that Miami-Dade County’s position hasn’t changed. If allowed to stand, despite the changes made by the Florida Building Commission, Miami-Dade County’s proposed implementation will not only weaken the new requirements for tile roof systems inside Miami-Dade and Broward Counties but will also have a far broader impact because a Miami-Dade County NOA can be used anywhere in Florida.

It is important to be aware that all of Florida acts as the reinsurer not only for Citizens Insurance (which is the largest provider of property insurance in the HVHZ) and the rest of Florida but also for many very small and historically shaky insurers. Property and casualty insurance purchasers in Florida are already paying a surcharge on their policies. When a strong hurricane hits a densely populated major metropolitan area, those surcharges could very quickly reach unsustainable levels. The effects on Florida’s economy and our individual insurance premiums could be devastating. It is clear that we need to do all things reasonable to mitigate the potential damage through stronger building codes. The positive impacts that strengthening FBC requirements have had cannot be disputed: post-hurricane damage assessments from many reliable sources have all come to the same conclusion. Sticking our head in the sand is not a viable approach. We simply can’t afford to let Miami-Dade County, which seems to rest its decisions on the fact that it “hasn’t seen the failures” set the standard. Such observations – or lack thereof – completely ignore the fact that they have not experienced a major hurricane since Andrew in 1992. The damage that we’ve observed where recent hurricanes have occurred clearly demonstrates that we should not weaken the code for the HVHZ and, through NOAs, the entire state. Building departments are not allowed to weaken the requirements of the code but apparently this may not apply to Miami-Dade County. It is also the only county that can issue product approvals through NOAs that can be used in other areas of the state. To paraphrase a bible verse: to whom much power is given, much discretion should be expected.

RCASF Technical Blog

What Can Be Done to Bring Them Around?

One of FRSA’s very astute Past Presidents and a member of our Code’s Subcommittee posed this question: “Why should it be up to our state roofing contractors’ association to attempt to enforce the decisions made by the Commission?” To put it quite bluntly, it shouldn’t! If we are going to successfully achieve the important goal of having strong and consistent underlayment and secondary water barrier requirements throughout Florida, we need all affected parties to help. For those of you who represent the insurance industry’s interest, we’ve lessened your exposure by strengthening building codes and pushed back against fraud because we know it’s the right thing to do. If you’re someone who wants improved roof resilience in order to maintain the availability of property insurance with reasonable premiums, you should consider making your voice heard. In particular, if you are involved in the construction industry in Miami-Dade or Broward County and share our concerns, please reach out to your Building Departments. Let them know that your customers need the level of storm protection and insurance premium consideration that is meant to be provided through these code improvements. We can’t accomplish this alone; we need your help. Our position is simple: test tile underlayments to failure, adjust for the safety factor of two and then post those uplift pressures on the NOAs in the same way that we currently do for Florida Product Approvals. As the Florida Building Commission recognized, this weak link is obvious and needs to be repaired. All the preparation has been done, the code has been published, all we need is a little cooperation from those interpreting it. We plan to work with building officials to help them understand the importance of verifying the proper pressures for permitting. Moving forward, FRSA will be looking at options to address our concerns but many of these take time that we don’t have. This issue should be resolved before the new code becomes effective at the end of the year.


Mike Silvers, CPRC, consults with FRSA as Director of Technical Services. Mike is an FRSA Past President, Life Member and Campanella Award recipient and brings over 50 years of industry knowledge and experience to FRSA’s team.

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