Hi Richard,
The builder probably means FBCR, or FBC-R, both of which mean the Florida Building Code, Residential. In the Florida Building Code series of codes, there is the FBC-B which is Florida Building Code, Building, then there is the is the FBC-R which is the Residential code, then the other codes are actually FBC-P (Florida Building Code, Plumbing), FBC-M (Mechanical), etc.
FBC really only means "The Florida Building Code" series of codes. Many use it when referring to the Building code of the Florida Building Code series of codes, which makes sense but is technically incorrect.
Likewise, the Florida Building Code, Plumbing is usually referred to as the FPC, which is also technically incorrect. The same applies to FMC (Mechanical code), FFGC (Fuel Gas code), etc.
I have noted on the reported the tread was 9 3/4" up to 10" tread is too small
the builder has stated that it did meet FBRC requirement and the reference to §1007.3.1 is incorrect
The reference you gave of 1007.3.1 is incorrect as that is from the 2001 FBC, which was replaced with the 2004 FBC series of codes in December 2005 if I remember correctly.
His reference, and yours, should have been to the 2004 FBC, Residential as this: (underlining and bold are mine)
- R311.5.3 Stair treads and risers.
- - R311.5.3.1 Riser height.
- - - The maximum riser height shall be 7¾ inches (196 mm). The riser shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).
- - R311.5.3.2
Tread depth.
- - -
The minimum tread depth, exclusive of nosing, shall be not less than 9 inches (229 mm).
Treads and risers of stairs shall be permitted to be so proportioned that the sum of two risers and a tread, exclusive of projection of nosing, is not less than 24 inches (610 mm) nor more than 25 inches (635 mm). The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread’s leading edge. The greatest tread depth within any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm). Winder treads shall have a minimum tread depth of 10 inches (254 mm) measured as above at a point 12 inches (305) mm from the side where the treads are narrower.Winder treads shall have a minimum tread depth of 6 inches (152 mm) at any point. Within any flight of stairs, the greatest winder tread depth at the 12 inch (305 mm) walk line shall not exceed the smallest by more than 3/8 inch (9.5 mm).
- - R311.5.3.3 Profile.
- - - The radius of curvature at the leading edge of the tread shall be no greater than 9/16 inch (14.3 mm).
Every tread less than 10 inches (254 mm) wide shall have a nosing or effective projection of approximately 1 inch (25 mm) over the level immediately below that tread. Beveling of nosing shall not exceed ½ inch (12.7 mm). Risers shall be vertical or sloped from the underside of the leading edge of the tread above at an angle not more than 30 (0.51 rad) degrees from the vertical. Open risers are permitted, provided that the opening between treads does not permit the passage of a 4-inch diameter (102 mm) sphere.
- - - -
Exceptions:
- - - - - 1. A nosing
is not required where the
tread depth is a minimum of 11 inches (279 mm).
- - - - - 2. The opening between adjacent treads is not limited on stairs with a total rise of 30 inches (762 mm) or less.
Attached is an annotated photo showing where riser heights and tread depths are measured.
Going back to your measurement and making some presumptions of those measurements:
I have noted on the reported the tread was 9 3/4" up to 10"
Presuming your measurement included the nosing (as this is a common way people measure treads), and the required nosing is the required 1 inch, that makes "the tread depth" itself only 8-3/4 inches to 9 inches, which is insufficient to meet the code.
Additionally, if the treads varied between 8-3/4 inches and 9 inches, the tread depth itself is insufficient as 9 inches is the minimum required tread depth.
Then there is the two risers plus one tread equals between 24 and 25 requirement which needs to be met in addition to the other tread and riser requirements. Thus, if the tread is 9 inches, then the riser heights much be between 7-1/2 inches and 8 inches high except that the maximum allowable riser height is 7-3/4 inches.
Thus, with a 9 inch tread the riser height would need to be between 7-1/2 inches and 7-3/4 inches in height for that to meet code.
Regardless, if you measured as I suspect you measured, that stairway *DOES NOT MEET* the requirements of the 2004 FBC-Residential.
Do you have any additional information you can provide as how you measured tread depth, if there was a nosing, the amount of nosing, and the riser heights? With that information I could provide a more detailed response of exactly what does not meet code, other than as it stand now with my presumptions that the tread depth is insufficient.