| Author |
Message |
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre
Post Number: 725
Registered: 07-2002
| | Posted on Tuesday, March 04, 2008 - 08:08 pm: |    |
Over the past few years, I've run into a number of situations where I've specified a thick, plastic (latex modified) setting bed (1-1/4" )for large format tiles, and the contractor has gone and installed a leveling course and then proceeds to thin set on top of the setting bed. Their contention is that they leveled the leveling course and that its suitable for thin-setting after that. I point to the TCNA manual that calls for a 1/2" notched trowel and ask how they are going to do that with a thinset installation.
What I'm looking for is some discussion about this method. I don't like the idea of it, and think that a thick plastic bed should actually be thick and plastic at the same time the tile is being set.
oh... and by "large format" I mean tiles or stones in the 12" x 30" size range, or 18" x 18", or something like that.
comments, please? |
Marc C Chavez
Senior Member
Username: mchavez
Post Number: 286
Registered: 07-2002
| | Posted on Tuesday, March 04, 2008 - 11:21 pm: | |
I had a tile contractor tell me that she only had 2 people that could lay a thick bed and do it right. (her dad and senior field super.) But she had many that could lay thin set. However, with large tile I think Anne has a point about pushing medium to thick bed as the combination of size, floor flatness and lippage will out strip the ability of thin set to level (flatten) the tile.
I'll ask my tile contractor and she what she says. |
John Hunter
Senior Member
Username: johnhunter
Post Number: 51
Registered: 12-2005
| | Posted on Wednesday, March 05, 2008 - 11:29 am: | |
I've heard the same comments from tile professionals here in Northern California - that no one is really able to install the wet method anymore. Also, in TCNA's commentary to ANSI A108, they note that industry practice has resulted in the large majority of mortar bed installations being installed according to ANSI A108.1B (cured mortar bed). TCNA doesn't help much by not having medium bed installation methods in the 2007 Handbook.
At any rate, since our firm seems to have fallen deeply in love with large format tiles (some as large as 24 x 48), we've added "thin-set mortar for medium-bed applications" to the products list and then refer to it in the installation method.
We're hoping this will allow the Contractors to use the cured bed method but keeps the thin set thick enough to keep enough mortar on the tile to address the lippage and other issues. |
Marc C Chavez
Senior Member
Username: mchavez
Post Number: 287
Registered: 07-2002
| | Posted on Wednesday, March 05, 2008 - 11:39 am: | |
OK I just talked to my tile Goddess.
She said that fresh set as she calls it (plastic or thick bed set) will certainly give you a great floor. HOWEVER you have to have tile setters that can do it. The vast majority of the trade simply cannot do that kind of work because they don’t ever get asked to. Therefore you will get some hollow tiles and failures. (Unless you hire her and she sends her dad out, who can do that kind of work)
She has no confidence that the tiles will be flat AND because of the weight involved in the new and larger tiles she recommends products like Laticrete 255 this product can be placed with a ½ inch notched trowel when you need bed thickness (for uneven floors or tiles) AND will support the heavy tile without sagging. It’s “glueyer” and does not come off things like your hands easily, but is well worth the pain when installing vertically or with large tiles. |
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre
Post Number: 726
Registered: 07-2002
| | Posted on Wednesday, March 05, 2008 - 01:35 pm: | |
apparently I also have to be more specific in specifying: the ANSI standard allows contractor option unless I take away that option:
The ANSI Ceramic Tile Installation Standards define each of these three variants as follows:
·1A – Installation of Ceramic Tile in the Wet Set Method, with Portland Cement Mortar
·1B - Installation of Ceramic Tile on a Cured Portland Cement Mortar Setting Bed with Dry Set or Latex-Portland Cement Mortar
·1C – Contractor’s Option (either 1A or 1B)
usually on our jobs, getting the mechanics isn't the problem, but I'll remind our staff to be more vigilant with the general contractors about this issue.
Marc-- you have a tile goddess?
A |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 14
Registered: 01-2008
| | Posted on Wednesday, March 05, 2008 - 01:41 pm: | |
I confirmed Marc's tile goddess statment regarding the availability of trained installers in our area who are technically capable of Installation of Ceramic Tile in the Wet Set Method, with Portland Cement Mortar. Option 1B was the prefered method. |
John Hunter
Senior Member
Username: johnhunter
Post Number: 52
Registered: 12-2005
| | Posted on Wednesday, March 05, 2008 - 02:16 pm: | |
I should have noted in the earlier post that we specify 108.1C (contractor selects method). Even though it is a medium bed application, the manufacturers identify their material as "thin set" so we've specified it as "Latex-Portland Cement Mortar (Thin Set) for medium-bed application: ASNI A118.4." We've identified the following products, although doubtless there are others: C-Cure K-Lite 929 Tile & Stone Mortar, Custom Building Products Medium Bed Mortar, and Mapei Ultralite Mortar. |
Christopher E. Grimm, CSI, CCS, LEED®-AP, MAI, RLA
Senior Member
Username: tsugaguy
Post Number: 123
Registered: 06-2005
| | Posted on Wednesday, March 05, 2008 - 02:50 pm: | |
Shrink-cracking is one issue I have heard to be careful of in a medium bed mortar. Some are more resistant than others. Also, check the 2008 TCNA. I think it is beginning to address medium bed. Mine's back at the office.
I also have this excerpt from the program summary of a recent talk for our CSI chapter:
Latex modified thinset is very widely used. Some installers may wish to add thinset to a thickset mudbed. You should verify with your manufacturer's rep for the installation involved. Thick set refers to 5 parts sand and 1 part cement for making a mud bed. This mud bed mix can be cast over a cleavage membrane and reinforce with wire mesh and allowed to cure. Then you can thin set tile to it (ANSI A108.1B). You can cast this same mud mix and bond it on grade where no bending stresses occur with a thin-set (bond coat), let it cure and thin set to it. Or you can cast this mud mix on or above grade and thin-set the tile into the wet workable mud (ANSI A108.1A). Or give the contractor his choice of curing mud and thin setting later or wet setting (ANSI A108.1C). Thin set bonds mud to floors and tile to mud. They do not mix together.
(That info courtesy of Chip O'Rear, Custom Building Products in Atlanta, (770) 329-0020 Cellular, chip@cbpmail.net - Chip delivered an excellent program) |
Dale Roberts CSI, CDT
Senior Member
Username: dale_roberts_csi
Post Number: 44
Registered: 10-2005
| | Posted on Wednesday, March 05, 2008 - 09:20 pm: | |
Hi Ann,
First let me be sure we are using the same terminology.
ANSI 1.3 the term “thin-set is not specific. “Thin-set” (dry-set) describes a family of products manufactured to be used as setting and or bonding coats. When a thin-set method is desired for which there is a specification, the appropriate ANSI specification should be referenced by both number and title.
Thinset (latex modified mortar ANSI 118.4) can be troweled on as thick as ¾” x 5/8” U-notch trowel. After beat in of tile or stone, mortar should be no thicker than ¼”, for thicker applications, use a medium bed mortar. Thin-set is not meant to true or level the substrate. Medium bed mortars (ANSI 118.4) are meant to level or true the substrates.
There are two methods to install tile using a Mortar bed (Floating, Mud work, box screed) ANSI A108.1 Wet Set method, with Portland Cement Mortar. And ANSI A108.1B Installation of Ceramic Tile on a cured Portland Cement Mortar setting bed with Dry-set or Latex Portland cement mortar.
Would you like to discuss the pros and cons of thin-set installations? Mortar beds? Both? And by Plastic setting bed are you referring to a wet set or a fresh mortar bed? |
Anne Whitacre, FCSI CCS
Senior Member
Username: awhitacre
Post Number: 728
Registered: 07-2002
| | Posted on Thursday, March 06, 2008 - 01:02 pm: | |
Dale-
by "plastic bed" I am referring to a wet set or fresh mortar bed at the time of the stone installation.
All of my tile or stone installations have a latex additive to them to allow them some movement capability in the finished installation. What I would like to see is a wet setting bed (full thickness) at the time of the tile or stone installation. My preference is for a medium or full setting bed underneath very large format tiles or stones (the stone manufacturers are saying that their products can be gaged and cut as finely as tile these days; in some cases, I treat them exactly the same). our typical stone module this year seems to be a 12" x 30" piece, 1" to 1-1/4" thickness. It baffles me to see a contractor thin setting something like this. |
Chip O'Rear (Unregistered Guest)
Unregistered guest
| | Posted on Thursday, March 06, 2008 - 12:30 pm: | |
30-40 years ago, before "thin-set" was invented, the "thick set" or "mud bed" method was the only way to install tile. The mud bed was wet, the tile was wet and the pure cement "bond coat" was wet, all hardening together (ANSI A108.1A- Wet setting). On grade, a mud bed could be bonded to the slab with pure cement and no wire reinforcing. Above grade where bending stresses could occur, a mud bed had to be wire reinforced and placed over a "cleavage membrane" to separate the tile work from the bending substrate.
Thin-set is 1 part sand and 1 part cement and contains water retentive chemicals so that a dry tile can be bonded to a dry substrate; this product changed the tile industry forever. This allowed for ANSI A108.1B- installing a mud bed, letting it cure and harden, then thin-setting tile to the cured, dry mud bed.
With the advent of waterproofing, anti-fracture and crack isolation membranes some 20 years ago, now tile can be thin set above grade subject to bending stresses over a resilient membrane performing the same function as a mud bed over a cleavage membrane. These membranes changed the industry forever.
Today, a waterproofing membrane (ANSI A118.10)(light duty anti-fracture)(F122) or a crack isolation membrane (ANSI A118.12)(heavy duty anti-fracture)(F125A) can be applied above grade then tile thin-set directly to the membrane rather than F111(wire reinforce med bed over a cleavage membrane). Thin-setting is considered faster, lighter, less expensive, thinner (no 2" depression) and time proven. True, mud work is still considered the best and most durable method as the contractor can control flattnes, hardness/compaction and slope if pitching to drains, but a good thin set installation over an appropriate membrane system is widely accdepted as a great and proven method.
Selecting the right membrane is critical as is using a premium latex modified thin-set (with resiliency itself) when thin-setting over a resilient membrane. Call your manufacturers rep for detials. Every major installation materials company makes these membranes and a variety of thin-sets; specify the proper products/systems by basis of design or you could end up with a miss-match of products not performing as you intend.
For thin-setting larger tiles, a "medium bed" thin set sould be used. Standard thin set should not be used thicker than about 1/4" or it can shrink and cause cracking. But, with larger tile, thin-set may need to be used up to 3/4" in total thickness after installation is complete. "Medium bed" is a thin set characteristic as is "non-sag" or "non-slump". To Mr. Grimms point above, one can install a mud bed (thick set), let it cure, then thin-set with a medium bed or standard thin-set to a thick set; common industry terminology can be confusing. |
Dale Roberts CSI, CDT
Senior Member
Username: dale_roberts_csi
Post Number: 45
Registered: 10-2005
| | Posted on Thursday, March 06, 2008 - 10:02 pm: | |
True Mortar bed installations (Thick Bed, Wet Set, Floating) are the most expensive and time consuming methods. They give you a flat, level floor, with the capabilities of sloping to a drain. They are also used if you are using different thickness (ungauged stone) of tile or stone and need to adjust or compensate for the different thickness in the finish materials.
Most of today installations (over 80%) are installed using the thin-set (dry set) method. You no longer need to recess the floor or worry about transitions of flooring material. This method is very fast, very inexpensive with lots of options. Options like, being able to use antifracture membranes under the installation. Mortar options include, Flexible mortars (absorb minor in-plane movement of the substrate), non-sag mortars (vertical installations), rapid setting mortars (for TI improvements set tile that night, traffic the next day), medium bed mortars (used for large format or heavy tile or stone, level or true substrates, ungauged stones), complete contact mortars (eliminate the need to back butter to achieve 100% coverage on the back of the tile or stone.
If you are concerned about the finish or lippage, you can specify the amount of allowable lippage. There is a chart in ANSI under workmanship regarding lippage and grout joint size guidelines. |
Dale Roberts CSI, CDT
Senior Member
Username: dale_roberts_csi
Post Number: 46
Registered: 10-2005
| | Posted on Thursday, March 06, 2008 - 11:21 pm: | |
AIA/CES Seminars direct to your office. We offer 19 different tile and stone seminars, covering everything from History, Surface Prep, Membranes, Sound Attenuation, Stone Use & Installation, Grout, Glass Tile installation, LEED, Mortars as well as others. All or seminars are AIA/CES Health Safety Welfare approved. All the seminars are free of charge and we provide the lunch. If you would like more information on tile or stone installations please email me at dalero@cbpmail.net |
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