Florida Inspectors, New (since 2020 FBC) requirements for roof sheathing

After recent fakebook posts went virtually unnoticed… it seems fakebook (for the record FB is a guberment created & run lnt3l coll3ction device, mark zuckabuck is a controlled meat puppet, yea just like p3do joe 0biden).

For some strange reason big cooperate builders don’t want anyone to know about this…

Let’s give this a try here.

In the 2020 Florida Building Code, the requirements for roof sheathing changed in a major fashion, roof sheathing is now required by Code to have minimum thicknesses determined by Windspeed Zones. Areas in Zones 140 MPH (Exposure C) and above require 19/32" sheathing (vs previous required 15/32") along with this change, came a change in roof nailing requirements. Longer nails with wider diameters are now required, By my assessment this affects a HUUGE portion of Florida. I have seen SCORES of improper installations in SWFL since I picked up on this. WE need to protect the People!


1 Like

Hi Dave, I found this from Floridabuilding.org…it may help illustrate further. Please vet it out, I am not in FL. Appears all of this went into effect 2021.


Thanks Brian great info also covers the new requirements for soffits I already have the Document but it could very well help others here.


So What does the exposure b,c and d mean?
Because B still allows 15/32"

Exposure B is basically closely spaced buildings with no open areas or water nearby (picture inner cities), Exposure C is Buildings near open areas or small bodies of water (like golf communities almost every new neighbor hood in our area), Exposure D is Buildings next to or near Large bodies of water. Most Plans I see for this area indicate Exposure C. Some (very few) indicate Exposure B but all were clearly Exposure C given site conditions.

1 Like

It’s really simple… :thinking: :roll_eyes: :sunglasses: LOL

1609.4Exposure category.

For each wind direction considered, an exposure category that adequately reflects the characteristics of ground surface irregularities shall be determined for the site at which the building or structure is to be constructed. Account shall be taken of variations in ground surface roughness that arise from natural topography and vegetation as well as from constructed features.

1609.4.1Wind directions and sectors.

For each selected wind direction at which the wind loads are to be evaluated, the exposure of the building or structure shall be determined for the two upwind sectors extending 45 degrees (0.79 rad) either side of the selected wind direction. The exposures in these two sectors shall be determined in accordance with Sections 1609.4.2 and 1609.4.3 and the exposure resulting in the highest wind loads shall be used to represent winds from that direction.

1609.4.2Surface roughness categories.

A ground surface roughness within each 45-degree (0.79 rad) sector shall be determined for a distance upwind of the site as defined in Section 1609.4.3 from the categories defined below, for the purpose of assigning an exposure category as defined in Section 1609.4.3.

  1. Surface Roughness B. Urban and suburban areas, wooded areas or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger.
  2. Surface Roughness C. Open terrain with scattered obstructions having heights generally less than 30 feet (9144 mm). This category includes flat open country, and grasslands.
  3. Surface Roughness D. Flat, unobstructed areas and water surfaces. This category includes smooth mud flats, salt flats and unbroken ice.

1609.4.3Exposure categories.

An exposure category shall be determined in accordance with the following:

  1. Exposure B. For buildings with a mean roof height of less than or equal to 30 feet (9144 mm), Exposure B shall apply where the ground surface roughness, as defined by Surface Roughness B, prevails in the upwind direction for a distance of at least 1,500 feet (457 m). For buildings with a mean roof height greater than 30 feet (9144 mm), Exposure B shall apply where Surface Roughness B prevails in the upwind direction for a distance of at least 2,600 feet (792 m) or 20 times the height of the building, whichever is greater.
  2. Exposure C. Exposure C shall apply for all cases where Exposure B or D does not apply.
  3. Exposure D. Exposure D shall apply where the ground surface roughness, as defined by Surface Roughness D, prevails in the upwind direction for a distance of at least 5,000 feet (1524 m) or 20 times the height of the building, whichever is greater. Exposure D shall also apply where the ground surface roughness immediately upwind of the site is B or C, and the site is within a distance of 600 feet (183 m) or 20 times the building height, whichever is greater, from an Exposure D condition as defined in the previous sentence.

Do we have any Engineers here that could explain how to fix this?
Wrong nails used for roof sheathing fasteners.

The problem I see is how many of the substandard nails were used. If you spaced them closer you may be able to get the same holding power. Unless your there when the roof sheathing was put on you wouldn’t even know if the correct nails were spaced properly. I would say you can’t effectively decide one way or another.

1 Like

Thank you for your input Sir.

I spoke with another Engineer yesterday (engineer listed on Plans for a certain property). I asked him some general questions and and then specific questions, He asked what this property was and I told him. His vocal posture changed and he gave a general answer, and said I’m not the person to settle this matter (in so many words). I thanked him for his time at the end of the call, unsolicited, he said you’re doing a good job

WOW, one Florida inspector interested in this information.

@dtews do you have any recommendations for this construction defect?

There is no magic solution here. If the sheathing needs additional fastener capacity, new fasteners have to be driven and finished with the roofing and underlayment pulled out of the way and then reinstalled. One step that is worth taking is to check the fastener spacing and running the actual calculation for pull-out. That might cut down on the number of additional fasteners that have to be installed.

I’ve heard there is a spray foam structural adhesive that can be sprayed to the roof sheathing truss connection providing additional uplift resistance.

Today’s inspection was interesting and sad, most of the newly built home had the correct nails installed, BUT, the wrong (15/32") sheathing installed. The small portion of the home (above the garage and a small part of one bedroom) had the correct sheathing (19/32") installed BUT, the wrong fasteners installed (0.113" x 2 3/8" ringshank nails, not 0.131" x 2.5 or 0.120 x 3" ringshank nails).
In July of 2020 I first read the new requirements of the 2020 FBC and drafted a narrative thinking this was going to be widespread. 3 years later this is the first one I’ve observed and unfortunately have to use a narrative I wrote 3 years ago. Now, experience has proven that the wrong fasteners are a much more common construction defect in this area.

1 Like