Tile/stone over CMU

[RobShepp]

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.

[Jerry Peck - Codeman]

[RobShepp]

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.....

[Jerry Peck - Codeman]

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.

[RobShepp]

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...

[Jerry Peck - Codeman]

I will repeat (this time keeping it short and simple) - that's not what 4407.4.6.1.2 says.

[Jerry Peck - Codeman]

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.