TAS 105 is a Florida Building Code test procedure used to determine the field withdrawal resistance of roofing fasteners. In simple terms, it measures how much force a fastener can withstand before it pulls out of the roof deck or substrate. This is particularly important for commercial roofing projects in Florida, where high winds and hurricanes can place significant uplift forces on roof systems. The Florida Building Commission identifies TAS 105 as the Field Withdrawal Resistance Test Procedure.
What Does a TAS 105 Test Measure?
A TAS 105 test evaluates the actual holding strength of fasteners installed in the existing roof deck. A qualified professional performs controlled field tests using the type of fastener and substrate specified for the roofing assembly.
The purpose is to determine whether the existing deck can provide sufficient fastener withdrawal resistance to meet the required design loads. This is different from simply checking whether a fastener appears properly installed. A visual inspection cannot reliably determine the actual withdrawal strength of an existing roof deck.
TAS 105 is therefore especially valuable during reroofing or roof replacement when the condition and strength of the existing substrate may affect the performance of a mechanically attached roofing system.
When Is TAS 105 Required?
TAS 105 is most commonly associated with mechanically fastened roofing systems, particularly during reroofing projects where fasteners will be installed into an existing substrate.
For projects in Florida’s High-Velocity Hurricane Zone (HVHZ), TAS 105 is specifically used for field withdrawal testing of mechanically attached roofing systems. Florida Building Code product evaluations also identify TAS 105 as the required field withdrawal test for mechanically fastened reroofing applications in the HVHZ.
Outside the HVHZ, TAS 105 may also be accepted or required depending on the applicable Florida Building Code provisions, roofing system, project specifications, and authority having jurisdiction. Some non-HVHZ applications may permit alternative field withdrawal testing procedures, such as ANSI/SPRI FX-1, where applicable.
Why Is TAS 105 Important for Commercial Roofing?
Florida commercial roofs must be designed to resist wind uplift pressures determined by applicable building-code requirements. If fasteners do not have adequate withdrawal resistance, the roofing system may be vulnerable to uplift during severe storms.
A TAS 105 test helps roofing professionals establish whether the fastener-to-deck connection can support the required design loads. Test results can also help engineers and contractors determine whether changes to fastener type, size, spacing, or attachment methods are necessary.
This is particularly important when reroofing an existing commercial building because the actual condition of the roof deck may differ from the assumptions used in the original construction documents.
TAS 105 vs. TAS 124
TAS 105 and TAS 124 address different aspects of roofing performance.
TAS 105 evaluates fastener withdrawal resistance—how well individual fasteners hold in the substrate.
TAS 124, on the other hand, is used for field uplift resistance testing of roofing systems, particularly where the performance of the installed roof assembly needs to be verified.
Choosing the correct test depends on the roofing system, attachment method, project location, and applicable Florida Building Code requirements.
Final Takeaway
TAS 105 is an important Florida roofing test that verifies the field withdrawal resistance of mechanically installed roofing fasteners. It is particularly relevant to commercial reroofing projects in Florida’s HVHZ and may also apply to other Florida projects depending on the applicable code and approved roofing system.
Before starting a commercial reroofing project, property owners and contractors should confirm the testing requirements with the project engineer, roofing professional, and local building official. Proper TAS 105 testing can help verify that the roof’s fastener connections are capable of resisting required wind loads and can contribute to a safer, code-compliant roofing installation.
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