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    Tile/stone over CMU

    Tile/stone over CMU

    New postby RobShepp on Sun Dec 14, 2014 11:43 am

    Good morning Jerry,
    I'm inspecting 10 new unit townhomes built in Dade county, 5 units per building. The builder applied decorative stone tiles(roughly 3/4"x4-6"x1-2") to two sides of each unit extending up to the second floor(units are 3 floors each)and in most locations I can look through the seems and see the CMU exposed. I am using chapter 44 of the FBC residential to understand that a continuous application of cement shall be used to mount the tiles, but I also thought a base coating of plaster was required underneath the tile? Chapter 7 sends you straight to chapter 44 when located in the HVHZ. I'm using reference R4407.4.6.1.2. This says the support shall be "continuous" across the back of the tile....what other reference to make my case for a required continuous backing am I missing? Thank you Jerry

    p.s. It was a pleasure meeting you at the FABI conference.
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    Re: Tile/stone over CMU

    New postby Jerry Peck - Codeman on Sun Dec 14, 2014 3:20 pm

    RobShepp wrote:The builder applied decorative stone tiles(roughly 3/4"x4-6"x1-2")
    .
    .
    I am using chapter 44 of the FBC residential to understand that a continuous application of cement shall be used to mount the tiles, but I also thought a base coating of plaster was required underneath the tile? Chapter 7 sends you straight to chapter 44 when located in the HVHZ. I'm using reference R4407.4.6.1.2. This says the support shall be "continuous" across the back of the tile....


    Rob,

    Not quite understanding the stone tiles - are they tiles of natural stone or manufactured stone? The size you listed is somewhat confusing - are you stating that the stone tiles are in 3/4" wide strips by 4" to 6" long (length varies) by 1/2" thick?

    Usually, tiles in strips that narrow (3/4") come on a backing in rectangular strips (such as 6" by 12") or in squares (such as 12" by 12").

    The "continuous integral support to the backing" would be that each separate piece was fully adhered to the backing, not that the masonry unit wall was covered with a continuous bed of Portland cement mortar (basically exterior thin set).

    In Miami-Dade and Broward counties efforts to overthink the building code as not being "good enough" for them (the HVHZ) they should have just stuck with structural matters and left the rest of the code stand, instead, they exempt out large portions of the code and substitute in "their better code" ... except that, in doing so, they lose what is in the code they exempted out.

    This is one example - the Residential Code for the rest of the state requires: (underlining is mine)
    - SECTION R703 EXTERIOR COVERING
    - - R703.1 General.
    - - - Exterior walls shall provide the building with a weather-resistant exterior wall envelope. The exterior wall envelope shall include flashing as described in Section R703.8.
    - - - R703.1.1 Water resistance.
    - - - - The exterior wall envelope shall be designed and constructed in a manner that prevents the accumulation of water within the wall assembly by providing a water-resistant barrier behind the exterior veneer as required by Section R703.2 and a means of draining to the exterior water that enters the assembly. Protection against condensation in the exterior wall assembly shall be provided in accordance with Section R601.3 of this code.

    The HVHZ section only addresses "Water resistance" in relation to: (underlining is mine)
    - R4402.12.6.5.2.6 Fiber cement shingle or tile panels.
    - - All fiber cement shingles or tiles shall resist a minimum wind uplift resistance as determined by Section R4403 for a roof slope of 9.5 degrees (0.0166 rad) and a roof mean height of 15 ft (4.6 m). All fiber cement shingle or tiles shall be tested in compliance with the following requirements. Wind driven water resistance in compliance with TAS 100, Physical properties in compliance with TAS 110, TAS 135 and uplift resistance.

    That is unless I have missed another reference to "water resistance" in the code.

    Most of what is exempted out for the HVHZ and replaced with special HVHZ requirements is not necessarily "better" and does not necessarily address what should be done and ends up being "not as good". Some of the HVHZ requirements are very good and very much needed, but those requirements should really apply across the entire state to every structure.

    It was a power struggle (politics) between South Florida and the rest of the state, with South Florida having the greatest centers of population and their own codes before the statewide Florida Building Code - even then, Miami-Dade had its own version of the South Florida Building Code and Broward County had its own version of the South Florida Building Code - they could not even agree with each other back then.
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    Re: Tile/stone over CMU

    New postby RobShepp on Sun Dec 14, 2014 4:21 pm

    The tiles are definitely panel strips, it's hard to tell how large they were originally as they are installed now. One thing for sure, I should not be able to see the CMU from the exterior.....Chapter 7 handles this quite nicely......chapter 44 muddles it all up and makes it confusing....
    Just thinking out loud here, but chapter 44 references wind uplift requirements of exterior components of the wall cladding, couldn't we say the chapter 44 is "in conjunction with" chapter 7? In other words, chapter 7 applies but structures located in the HVHZ also have to meet certain uplift and wind requirements besides the normal water-resistance? This is really reaching, but R4407.4.6.1.2 says that tiles are required to be mounted with a continuous base of Portland cement over masonry, Portland cement installed over masonry is required to be two coats 1/2" thick. Or, some variance of that.....
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    Re: Tile/stone over CMU

    New postby Jerry Peck - Codeman on Sun Dec 14, 2014 6:01 pm

    Chapter 7 exempts out the HVHZ from Chapter 7 and directs the user to Chapter 44.

    Portland cement is not required to be any number of coats or of any thickness. The application of Portland cement products depends on the Portland cement product.

    I suspect you are trying to apply the application and standards of stucco to the product applied as mortar to adhere those tiles to the masonry wall substrate. - stucco is a different product intended for a different use.

    Now, if Chapter 7 waited until further down in the chapter to exempt out the HVHZ, then one could presume that the Chapter 7 requirements above the point of being exempted out would still be applicable ... except that Chapter 7 exempts out the HVHZ at the very beginning of the chapter.

    Did you add the photos to the first post? I didn't see the photos there before.
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    Re: Tile/stone over CMU

    New postby RobShepp on Sun Dec 14, 2014 9:40 pm

    Yes, I forgot to add the photos until after I posted. You can see the CMU exposed behind the tiles/stone clear as day....my notes are leaning towards removal as there is no way to adequately seal all the seams between thew tiles. I think I found a way around it though, R4407.4.6.1.2 says the backing shall be continuous across the backing for support...with the exposed gaps the argument can be made that the cement is not "continuous across the backing" and therefore not installed per code. At least that's what i'm thinking...
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    Re: Tile/stone over CMU

    New postby Jerry Peck - Codeman on Sun Dec 14, 2014 10:09 pm

    I will repeat (this time keeping it short and simple) - that's not what 4407.4.6.1.2 says.
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    Re: Tile/stone over CMU

    New postby Jerry Peck - Codeman on Mon Dec 15, 2014 11:13 pm

    Rob,

    Think of it this way:

    If I set 12" x 12" tiles on the wall in a checker board pattern, leaving 12" x 12" openings between the tiles, what would the purpose be of spreading thin set mud over the open areas?

    The requirement is to make sure the tiles stay in place, so the requirement would be that the tiles are set in a continuous bed of mortar.

    If I reduced the tiles down to 3/4" by 6" and spaced the tiles 1/4' apart, the same applies - it is the tiles which require the full continuous bed of mortar, not the substrate.

    Granted, with 12" by 12" tiles, buttering the back of each tile and setting it to the substrate it is no big deal, while buttering the back of each 3/4" by 6" tile and setting it to the substrate would take a lot of extra work - it would be much easier to spread the thin set mud on the substrate and then set the tile in the mud ... but that is not the requirement. The requirement is for each tile to be set in a continuous bed of mud ... it is the tile which the code wants to stay in place.
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