Interpretation #9489
Published February 03, 2026
Original Request
- Code Version
- 2023
- Code
- RESIDENT
- Code Description
- Chapter
- 9
- Section
- 905.1.1
- Topic
- ZIP System Roof Sheathing
Question
Florida Product Approval 17146 was recently revised to correct an error (typo) within the supporting evaluation report which referenced the wrong underlayment method in the Florida Residential Building Code. Based on this correction and subsequent revision to the product approval, would using ZIP System on a roof slope 4:12 or greater require an additional layer of underlayment under asphalt shingles?
Answer Published 01/22/2026 at 12:16 PM
If installed as per manufactures recommendations, Zip systems sheathing will meet the code requirements of 905.1.1 if used for asphalt shingle applications only. If other roofing materials will be used, (clay tile) then additional secondary water barrier would be required. So, the answer depends on the type of roofing being applied. If installing clay or concrete tile roofing, a second underlayment is needed regardless of slope. See section 2.3 of the revised evaluation report in FL17146-R12.
Please refer to interpretation 9468 regarding the change made by the Florida Building Commission to the product approval.
Please refer to interpretation 9468 regarding the change made by the Florida Building Commission to the product approval.
Commentary
None.