Block made with Florida limestone normally has a density per cubic foot of 120 to 124#. This puts it in the upper end of the C90 classification of Medium Weight block (Table 2 - C90-14).
NCMA TEK Note 13-01C gives an STC rating of 47-48 for an 8" hollow unit with a density of between 115 and 125 #/CF.

Links to additional documentation:

​https://ncma.org/resource/sound-transmission-class-ratings-for-concrete-masonry-walls/

he C129 spec is a less restrictive version of the C90 spec.   Any unit meeting the C90 spec will also meet the C129 spec. Additionally, the individual block strength of 2800psi is a pretty much meaningless number.  In editions of the TMS 602 prior to the 2013 edition the 2800psi block strength gave you an f'm=2000psi.    In editions of the TMS 602-13 the required strength of block to achieve f'm=2000 reduced to 2000psi (one to one).   A block with a strength of 3250psi now yields an f'm=2500psi - which is now the new high strength block.    A standard block (every C90 block) is now an f'm=2000psi.   The required individual block strength for C90 has increased from 1900psi to 2000psi which, again, yields an f'm=2000psi.    Specifying an individual block strength of 2800psi means that the specifier is looking at the OLD code.    This is explained again in the blog below.    Good luck with your project!  Call if you have questions.   The specifier is welcome to call me also.

Detailed Question: We have had several jobs recently specifying “high Strength Block”. Some has listed 2500 psi another I believe was 2800. Looking at C90 it seems to be open to interpretation and maybe job specific? We have a HS block but just trying to make sure we are fine. Is there a specified strength for this classification?

Detailed Answer: There are generally two block strengths that are readily available to the structural designer. For the sake of simplicity I will call them ""normal"" and ""high"" strength. The strengths have changed dramatically since January 1st, 2018. The new strength values for masonry come from either the 2013 or the 2016 edition of the TMS 602 specifications section 1.4B.2.b.Table 2. The Florida Building Code, 6th Edition, references the 2016 TMS 602 but the strength values are the same in both editions (and will be in future editions).

The compressive strength of an individual block of ""normal"" strength is 2000 psi which can be used to build a wall with an f'm=2000 psi.

An individual ""high"" strength block would have a compressive strength of 3,250 psi and would result in a wall with an f'm=2500 psi. This ""high"" strength block is stocked on some yards but is readily available on demand from most manufactures with minimal delay and only a slight increase in cost.

Walls designed with an f'm=2750 psi require that the individual block unit has a compressive strength of 3900 psi. These block are available from manufactures throughout Florida but are going to result in longer lead times (because they are almost never stocked). You can expect significant additional cost and longer holding times after manufacture to make sure they will achieve the required strength.

I would not recommend specifying masonry with a compressive strength f'm=3000psi. This strength requires an individual block with a strength of 4500 psi. This strength is closing on the natural limit of masonry produced with Florida aggregate. If you require a masonry unit of this strength consult with your block supplier on cost and availability. You will most like find that you are going to be better off specifying a "normal" strength 12" wide unit which is available off the shelf everywhere.

You would never put tyvek on a masonry wall.   I have never heard or seen such a thing.   The code does not require a “vapor barrier” on cmu .   Your block either has integral water repellent in combo with an exterior sealant/paint ----- or ------ it is stucco’d in which case the stucco and paint in combo with the cmu becomes the water/vapor barrier  ------ or---------- you put brick on the outside with a roll on barrier  ------ or---------- if you are using direct adhered stone or thin brick you use a product that seals the wall and adheres the stone or thin brick.  
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In all cases,  other than at cracks - which need to be addressed in the design, the wall is water tight and sufficiently vapor tight to keep the interior dry.

​The prohibition to connecting infill masonry to the surrounding frame in TMS 402-16 Section B.3.2 only applies to in-plane forces in participating infills.  The reason is explained in the commentary for that sections which explains that this is to prevent the connectors from causing ""premature damage along the boundaries of the infill under in-plane loading (Dawe and Seah (1989a))"".  
The Florida code is requiring connection for out of plane loading from wind which is also required by Section B.3.3 of TMS 402.

See also: https://masonrysociety.org/product/tms-402-602-2016/

We are working on an existing building and need to know if the exterior 8" masonry walls are 2 hr fire rated in order to make a determination as to the Building Type. The exterior walls are covered in direct applied stucco and the interior walls are covered with gypsum drywall. Can we be reasonably sure that the walls, with stucco and drywall, meet the requirements for 2 hours?

The only way to be 100% sure is to remove 6 block intact from the structure and send them to the lab to be tested to determine that they meet the requirements of C90 and what the equivalent thickness of the units are in accordance with C140. you would also need to verify that the material used in manufacturing the units is limestone.

All that being said, you can make some conservative assumptions and be relatively certain that the walls meet 2 hours using the provisions of Chapter 7 of the 2017 Florida Building Code 6th Ed., Building.

Since 99.9% of all block manufactured in Florida use limestone as the main aggregate you can safely assume that the block in the building are limestone based, thus requiring a 4" equivalent thickness in accordance with Table 722.3.2.

The least equivalent thickness for any block regularly produced in South Florida is 3.6 inches. An example of this would be the CEMEX T007. Thus 3.6 would be a conservative assumption for the block used in a building in SW Florida. Interpolation of the table is allowed so that 3.6" gives you 100 minutes. Thus, you are .4" and 20 minutes short of your required 2 hr rating.

Section 722.3.2.1 gives you directions on how to calculate the fire rating value of finishes applied to the non fire-exposed side of the wall and Section 722.3.2.2 gives you directions on how to calculate the value of finishes on the fire-exposed side. These sections refer you to Table 722.2.1.4(1) for the non fire-exposed side and Table 722.2.1.4(2) for the fire-exposed side. If there is doubt from which side the code is requiring the rating the best thing is to calculate from both side and take the least value.

Conservative assumptions on the wallboard and stucco would be 1/2" wallboard and 3/8" (.375") single coat stucco (the stucco would not be to code but would be conservative for the purpose of calculating a conservative value of the fire rating).
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Running the calc with the fire side assumed as the exterior you get:

• Stucco value from Table 722.2.1.4(2) (note a.) - .375"
• Wallboard value from Table 722.2.1.4(1) - 3x.5"=1.5"
• Total equivalent thickness = 3.6+.375+1.5=5.47">4" OK
• Running the calc with the fire side assumed as the interior you get:
• Wallboard value from Table 722.2.1.4(2) - 15 min
• Stucco value from Table 722.2.1.4(1) - .375"
• Total equivalent thickness = 3.6+.375=3.975"=1 hr and 58.75 minutes.
• Adding in the wallboard value of 15 minutes you get 2hr and 13.75 minutes > 2 ok.
• Thus, a reasonably conservative assumption would be that your wall meets a 2 hr rating.

​The most likely cause is normal block shrinkage.   Standard control joint spacing would call for a control joint about mid way in your 40' long wall.   Sounds like mother nature has taken care of supplying that.  You also might check for aggravating circumstances such as an interior partition at approximately that location with a vertical row of fasteners. 
If the crack is the same width at the top as at the bottom my guess is that it is not caused by settlement. 

​No, The #5 does not provide as much strength because the distance between the center of the bar and the compression face of the masonry is not a far and the strength depends on that.    However, the bending strength in the other direction is considerably more.   Alternating the side that the steel is on could make a big difference in the overall bending strength when checked in both directions.

How big can a but joint be in face brick on wood studs? How much of a variance can there be in but joint sizes with tumbled brick?

I believe I am seeing two completely different questions. one is in regard to the material that will used as the substrate in your wall assembly. You will need to contact your local building department to solve the issue of fire-treated vs non combustible plywood. As far as staples in gypsum board, that method should not be used. Adhered veneer is supported by the substrate it is applied to thru the lath and the anchors used to attach the lath. I am attaching a couple of items that will give you direction on the assembly.

One item to read is ASTM C1780 Standard Practice for Installation for Adhered Manufactured Stone Masonry Veneer. Even though this Practice does not include thin brick, the substrate preparation is relatively the same. Another document is BIA Tech Note 28c for Thin Brick Veneers. It is an excellent reference document. If you know the brick and its manufacturer additional information technical information is generally available on their website.
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I hope this is helpful in designing and constructing a beautiful and functional thin brick.
Jerry Painter, FASTM

The "STC" or Sound Transmission Class of a brick can vary based on thickness, hollow or solid, and textured finish among other things. The Masonry Society has a publication called TMS 302 Standard Method for Determining the Sound Transmission Rating for Masonry Walls. It helps calculate the STC of a wall. There is a BIA Technical Note # 5A. It describes a typical 4" brick as having a STC of 45. The best way to determine the STC of brick is to contact your local brick distributor. They should be able to give you the value of the specific brick you want to use.

Links to additional information:

​TMS 302 Standard Method for Determining the Sound Transmission Rating for Masonry Walls​

BIA Tech Note 5A Sound Insulation - Clay Masonry Walls