Ask the Experts – May 2018

Ask the Experts Q&As are culled from member inquiries to NTCA’s Technical Support staff. To become a member and make use of personal, targeted answers from Technical Support staff to your installation questions, contact Jim Olson at [email protected].

QUESTION

I recently installed 2” x 2” sheet-mounted mosaics in a public park bathroom. During the tile installation the general contractor provided me with limited lighting. Electricians installed LED light fixtures above and against the wall. 

During the installation, the owners of the facility were very pleased with how the product looked on the walls. But I noticed that with these very bright lights located directly over the tiles, you could see imperfections. Plus, shadows from the lighting made the tile job look like it was not done well, but when you ran your hand against the tiles you could feel that it was done properly. 

A couple of months later they contacted me for a meeting to go over the installation of the tiles because they felt it was unacceptable. When I arrived the owners went over some of the areas and claimed that I did not do a good job. I did notice some tiles that needed to be replaced, but for the most part they were installed very well. I told the owners that I do not have a problem going over quantities that needed to be replaced and that I would take care of it; we even went to another facility where a different installer installed the same type of tile but the light in that room was not directly against the wall and you could not see the cast shadows – but when you ran your hand again the wall you could feel the imperfections. The bottom line is that the owners want me to replace the whole wall, which it is not necessary to fix the problems. I also documented during the process pictures that the drywall was not properly installed and leveled, and that was another reason for the imperfections. 

Can you provide to me or help me with some sort of literature or a reference to a handbook so I can protect myself from being taken to court, when clearly this is an issue because of the way the lighting fixture is located and it’s casting shadows, making the installation unacceptable. I did find some information about this topic but I do not know how to approach this to avoid court. 

ANSWER

The situation that you have found yourself in is very common to our industry. We have received several technical calls about the influence of lighting on finished tile work. The design community has embraced this type of lighting to give a more dramatic lighting effect. Any type of lighting located on or near tile walls accentuates irregularities by casting shadows on the tile surface.

The good news is, our industry has addressed this issue in several places: in the TCNA Handbook, page 34; in the NTCA Reference Manual from page 121 to 127; and in the ANSI standards on page 26.

There are allowable amounts of lippage in any tile installation. There are charts in both the ANSI standards and TCNA Handbook based on the type of tile, tile size and joint width. Attached is an image of Flatness and Lippage table on page 36 from the TCNA Handbook, versions 2017 and 2018 (image courtesy TCNA).

In summary, our standards say that the angle of light cast on tile work can accentuate otherwise acceptable variance.

We have had members bring lights in to a situation like this, taking photos of the same wall under two different lighting influences. This can be dramatic and show the impact lighting has on the appearance of a installation. Attached is an image from the NTCA Reference Manual showing the same wall with two different lighting options.

As far as the surface not being flat enough to start with, there are standards for how flat a surface should be to install tile. The surface should have no deviation (hump or dip) of more than a 1/4” in a ten foot radius. As far as the substrate not being correct and affecting the installation, this should have been addressed prior to the installation. Once we start an installation we have accepted the substrate as suitable. Once we start tiling a surface
we now own it. 

Robb Roderick,
NTCA Trainer/Presenter

Ask the Experts – March 2018

QUESTION

I am a homeowner having a glass tile install performed. The tile is a 3” x 12” glass subway tile with a color backing. It is being installed as the backsplash around the stove/oven. My tile contractor said to butt the glass tiles up to each other with no spacing in between – and to butt them up to the quartz countertop – but I was told by the tile store to use a 1/8” spacing.

All I am looking for is your technical opinion on the proper way to install the tiles regarding the spacing to give some instruction to my contractor for the install. The tile edges/corners are flat with no bumpers that would cause a spacing when they are butted up to each other.

ANSWER

We always encourage our members to follow the guidelines set forth in the TCNA Handbook. On page 37 of the Handbook it states “that in no circumstances shall the grout joint be less than a 1/16 of an inch.”

One of the reasons listed for a minimum requirement for grout joint size on all tile installations is “thermal expansion.” Glass tile is highly expansive. It also explains that the grout joint should be no smaller than three times the variation of the tiles themselves. That means if a particular group of tiles vary in size 1/16”, the smallest grout joint recommended for that particular group of tiles is 3/16” of an inch.

Most glass tile manufacturers have directions for the use of their products. I would encourage you to contact the manufacturer of the glass to get their recommended grout joint size. And make sure there is the appropriate sealant joint where ever the tile meets differing materials like a countertop or cabinet.

I hope this helps.

Robb Roderick, NTCA Technical Trainer

QUESTION

I plan to have a small bathroom tiled, shower walls with niche, shower floor, and floor (12” x 24” walls and 4” hex all floors). This is on concrete slab.

I’m working with a contractor who is bringing tilers in for the job and I’d like to make sure they are following standards. Can you tell me what the acceptable methods are for building/waterproofing a mud-pan, including shower wall and threshold?

I know they are creating a mud pan, but not sure what products or method they are using. I’m assuming there are a variety of products used and methods, which makes it complicated for the lay person. Any information/diagrams are appreciated.

Thank you!

ANSWER

You are correct that shower construction is complicated. It is critical that a shower is constructed properly.

Depending on the specifics of your installation, there are several methods for constructing showers published in the 2017 edition of the TCNA Handbook for Ceramic, Glass and Stone Tile Installation. These will guide a contractor who owns and uses them.

These methods include: B414, B441, B415, B420, B426, B431, B421, B422, B421C, B422C. These methods may vary somewhat depending on whether ceramic/porcelain or stone tiles are being installed. In addition, the Handbook contains several details for common configurations for curbs and membrane installation.

You are also correct that there are a variety of products on the market that are excellent for constructing successful shower and tile installations. Many of these materials meet or exceed the ANSI A118, ANSI A137.1 and ANSI A137.2 standards. A knowledgeable installer and contractor will be able to identify the appropriate materials and relate them to the TCNA Handbook method that is most appropriate for your installation.

If your contractor is a member of the National Tile Contractors Association I would be happy to speak with them and assist them with any questions or concerns they may have in selecting the appropriate method for constructing your shower. If your contractor is not a member of the NTCA, I would be happy to speak with them about becoming a member, and all of the professional benefits membership provides. A search for an NTCA member contractor near you can be done at this link: http://tile-assn.site-ym.com/search/custom.asp?id=2759 or http://bit.ly/2FJiak6.

I highly recommend employing a Ceramic Tile Education Foundation (CTEF) Certified Tile Installer (CTI). CTIs are installers who have proven their knowledge of skills in applying industry recognized standards, methods and best practices to ensure you get the correct installation from the substructure to the finished tile surface. CTIs can be located at this link: https://www.ceramictilefoundation.org/find-certified-tile-installers or http://bit.ly/2CSu5Jf.

I hope this helps!
Mark Heinlein – CTI #1112, Training Director,
Technical Trainer / Presenter

Ask the Experts – February 2018

QUESTION

We found the stress cracks in the floor several days after the tile was installed. I had never seen anything like this in my 40 years of being in the trade, and neither had my tile man. They showed up as slightly wavy white lines in the marble. There was not a black line or crack you feel.

We removed a couple of tiles where two stress cracks intersected. The tile was well bonded to the 1/2” cement board below the tile. There was no intersection of sheets of cement board below the crack. The cement board looked sound. We removed the cement board to expose the tongue-and-groove plywood subfloor below. Where the cracks intersected in the floor was exactly where a sheet of plywood stopped and started. The cracks lined up with long 8’ run and one 4’ run. So, somehow whatever movement took place in the sheet of plywood transferred up through the cement board to the tile. There were no cracks in the cement board and it was firmly bonded to the plywood.

We took up all the tile and cement board. We checked the subfloor with a laser to see if the floor was showing any signs movement. The entire floor was within 1/8” of level everywhere we checked. There were no ridges in the plywood where the sheets butted together. The only suspicious thing I found was an area along the 8’ side of the plywood where the tongue of one sheet was not fully engaged in the groove of the other. This meant that there could be more flex in the plywood than there should have been.

We removed the sheet of plywood and checked the framing. The new joists we sistered onto the existing joists were 2” x 8”. They were nailed soundly to the existing 2”x 10” that were all over 2” thick. These joists spanned from the living room wall to the exterior wall. They also pass over the wood columns and beams that divide the stair well from the entry hall. The floor platform was really strong and robust. The plywood had been installed with construction adhesive and ring shank nails. It was fully bonded to the framing and very difficult to remove.

We could not see any good reason why the tile came to show the stress cracks. The only reason that I could come up may have had to with using adhesive to bond the plywood to the framing. I have seen problems in other areas due to adhesive shrinking as it dries. We have found when wall board is installed with adhesive and screws that the screws and plaster above them can show up as little humps on the surface of the board as the adhesive dries and pulls the wall board closer to the framing. It is only a fraction of an inch but I have seen this happen many times before – as the board moves closer to stud and the screw stays fixed, you get a hump.

This is only a theory but if the plywood got pulled tighter to the framing as the glue dried, could that small shift in the floor sub floor cause the crack in the tile? Total guess.

Also the non-fully-engaged tongue could have had something to do with it on the long side. Though short side of the ply was firmly seated on a joist, and we had stress crack here, too.

Marble is much softer than other stones or porcelain tile. Like I said before, I have never seen this happen before and we have used this type of assembly successfully for many years.

Anyway, we decided to add rows of blocking between the joists along the 8′ length to make sure that side of the plywood was more secure. We re-installed the plywood and were planning on using uncoupling membrane under the tile to avoid further stress cracks in the marble.

I suggested to the client that he might like another type of floor material to avoid any other chance of this happening again due to the softness of the marble. I understand everyone’s reluctance to do this, but I just wanted to increase our chances of having no further complications.

The tile installer feels pretty confident the uncoupling membrane will do the trick. My stone guy examined our tile and he said the product was as sound as you are going to get with Carrara marble.

What do you think?

ANSWER

Good to hear from you. As you are aware, the NTCA always encourages people to follow industry guidelines set by both the Tile Council of North America (TCNA), and American National Standards Institute (ANSI).

I was able to read the correspondence about this stone tile failure. The questions raised are covered in our industry standards.

The assembly that failed was a backer board installation over plywood. Attached is the diagram from the TCNA Handbook method F250, which is the closest method to what was described. If you notice two layers of plywood are required underneath the backer board install. For a similar installation using ceramic only one layer of plywood would be required. That detail is found in method F144 on page 162 of the 2017 TCNA Handbook.

There are two standards for allowable deflection in tile installation. For ceramic and porcelain tile, the standard is L/360. For stone tile installation the standard is L/720.

The L in this equation is the length of unsupported span under the installation in inches. This means that only half of the movement which would be allowable with a ceramic install would be allowable with a stone installation.

The question about adhesive under the plywood against the floor joist is addressed in ANSI A108.11 it states “…a 1/4” bead of construction adhesive should be applied to the center of the top of the joist and the plywood fastened to joist with 6d ring shank nails. There should be a 1/8” gap between the subfloor sheets.”

There was a mention of using an uncoupling membrane for the second installation. A second layer of plywood is required when using uncoupling membrane. Check with the uncoupling membrane manufacturer for complete instructions on this type of installation.

I hope this information helps. – Robb Roderick, NTCA presenter/trainer

Ask the Experts – January 2018

QUESTION

I’m having issue with glass tile for one our customers. We’re trying to determine what’s causing the cracking. I believe it might be due to the thinset shrinking. Is it possible that it may be the tile?

ANSWER

Yes, it is possible that the glass cracking could be due to thinset shrinkage as it cures, especially if the maximum bond coat thickness of the thinset was exceeded. But looking at the two photos you sent, here are my guesses.

In the first photo that includes the glass door and hinge, it appears that the glass may potentially have cracked from:

  • over-tightening of the screw through the hinge
  • a minor misalignment of the hole drilled in the glass to accept the screw
  • weight of the door on the fastener at the pressure point if all components of the door installation were not properly aligned or balanced.

In the second photo showing the closeup of the grout joint, it is difficult to know what caused these small fractures. The photo is taken too close to see a context of the location in the shower. It appears that the photo was taken very close to the glass and the fractures are fairly small. My guess is the fractures may have been in the tile at the time it was installed and they weren’t noticed by the installer.

If you need a solid determination of these fractures, a third party consultant that can make an onsite evaluation may be needed.

I hope this helps.

Mark Heinlein – CTI #1112, NTCA Training Director, Technical Trainer / Presenter

QUESTION

We are members of NTCA and would love some technical advice on thin panel installation.

We are supplying large-format, thin porcelain panels for an exterior façade in Oakland, Calif. It is approximately 2,500 sq. ft. at 102˝ x 47˝ x 6.5mm and we are researching installation options for the owner that do not involve the normal setting method.

It would be great to know what options there are for a “rail & clip” system versus full contact installation.

At the very least, it would be great to get some information on the guidelines and practices for installing thin panels using some sort of clip or fastening system.

ANSWER 1

Thanks for contacting us. I took a quick look at the manufacturer’s instructions. They are very typical of most gauged porcelain tile panel manufacturers. I did not see anything other than the direct bond method as an option for installation. Most distributors of thin porcelain tile have been working with installation product manufacturers and tool companies to present a system approach to installation. Some even require the use of manufacturer trained installers.

Last April there were new standards added for this product. ANSI 137.3 and ANSI 108.19.

ANSI 137.3 deal with standards for the product itself. ANSI A108.19 deals with the installation of the product.

I would encourage you to reach out to the manufacturer to see if they would recommend another fastening system. We always encourage our members to follow manufacturers’ instructions explicitly. It decreases your liability in projects.

Robb Roderick, NTCA Trainer/Presenter

ANSWER 2

Thank you for contacting our NTCA Technical Team with your question.

Robb is correct. ANSI A137.3 and ANSI A108.19 are the industry standards adopted this year for the production and installation of gauged porcelain tile and panels/slabs. These standards call for the installation of this material in a thin-bed type system with special emphasis on the installation process for floors and walls outlined in A108.19.

As Robb stated, it is important to follow the tile manufacturer’s instructions. Contact them to be sure you understand their instructions thoroughly. Deviation from installation instructions can result in lack of warranty coverage and/or acceptance of risk by the installation contractor.

The Tile Council of North America (TCNA) has the new standards available on its website for electronic download and it is taking pre-orders for a limited-edition hard copy. You can find the information to purchase an electronic version or reserve your hard copy on the TCNA website www.tcnatile.com/products-and-services/publications/218-english-publications/227-ansi-a137-3-and-a108-19.html or http://bit.ly/2i4iP4p.

Local codes will likely have specific requirements for installing tile above a certain height, especially on an exterior.  Please be certain to contact the code official responsible for the municipality this installation is located in.

Many setting material manufacturers make specialty mortars for installation of these tiles.  You will want to involve your setting material manufacturer to help you determine the best mortar for the application and ask them to work with you to write a site-specific system warranty based on their instructions and industry standards.

I am not aware of any mechanical rain-screen type fastening systems for use with gauged porcelain tile/panels; however, some tool and equipment manufacturers make a clip-type system that is used in conjunction with a thin-bed bond coat installation to provide additional mechanical attachment of large tiles in a vertical installation. One such system is manufactured by Raimondi. For more information about that system please contact Donnelly Distributing/Raimondi USA at 262-820-1212 or [email protected]

Mark Heinlein – CTI #1112, NTCA Training Director and Technical Trainer/Presenter

Ask the Experts – December 2017

This month’s Ask the Experts focuses on two recent questions concerning installing resin-backed stone.

QUESTION

Can you give me some guidance on working with resin-backed stone?

ANSWER

The issue that we have with resin-backed stone is there is no standardization. The backing could be composed of epoxy, polyester, urethane or a variety of other types of resin.  If there was some consistency to the resin backing, setting materials manufacturers could probably produce thinset that would work. Epoxy adhesives are the safest bet, and should always be used on moisture-sensitive stone.

When installing resin-backed stone, you should contact the stone provider for installation instructions. Many of them are not suitable for installations in wet areas.

The 2017 TCNA Handbook addresses some of this in the Natural Stone selection guide on page 10. The NTCA Reference Manual has a tremendous amount of information about this situation in its mesh-backed stone white paper on page 179. Both will point you toward the use of epoxy adhesives.

Somemanufacturersoftheseresin-backedstoneshaveincorporatedsandandotheraggregatestotheirbackingstohelpwithamechanicalbond,andmakeclaimsthatalatex-modifiedthinsetcanbeused.Iknowpeoplehavescarifiedandorprimedthebackofthesetilesinordertousemodifiedthinset.Withouttheendorsementofthethinsetmanufacturerandthestoneprovider,theseinstallationsarerisky.Iwouldproceedwithcaution.

Robb Roderick, NTCA trainer/presenter

QUESTION

I installed a large resin-backed marble tile on a fireplace wall with a glass-covered fireplace insert that produces a lot of heat, and measured tiled surface temp was about 250+ degrees in direct vicinity of the firebox. I have several issues.

Issue one – We used a polymer-modified thinset to install the tile.  I didn’t realize till after the job was done that it does not stick to resin-backed tile.

Issue two – Upon further research I should have used an epoxy thinset, but from what I was told it is only okay for temps up to 180 degrees.

Issue three – Is the resin on the back of the tile okay to be in contact with that kind of heat?

I am receiving very little help from my tile supplier, I have a very unhappy client, and I am eager to make the fix but I need to know the correct approach so I don’t have a problem again.

Thanks in advance for your help.

ANSWER

There are no industry standards for the resin/resin-mesh backing on stones. The best way to learn what the resin is composed of and what its temperature rating is, is to get the information on it from the manufacturer or stone quarry that put it on the stone, or a lab can examine it. I personally do not have information on the temperature ratings of various resins used on stone backing.

You can reference the NTCA’s Mesh Backed Stone and Tile White Paper (see the Stone section in this issue, page 78 for the paper), which discusses the other issues you described. This information should help give you a better understanding of the application of resin-backed stones in various installations.

It sounds like you will be considering a tear-out and rebuild to ensure that you achieve the proper bond and meet the temperature range of this particular fireplace. I suggest contacting the stone manufacturer/quarry to determine the type of resin, or if that isn’t possible, replace it with a stone that is not resin/resin-mesh backed. I also suggest contacting the manufacturer of the setting materials (i.e. thinset mortar or epoxy and grout) that you will plan to use to set the stone. Many product Technical Data Sheets include this information and can be found on their manufacturer’s websites, or a call to their technical service department will help you determine the correct setting materials to withstand the temperature ranges for this product.

Mark Heinlein – CTI #1112, NTCA Training Director and Technical Trainer / Presenter

TECH TIP TUESDAY: ASK MARK – 11/28/17

Contractor Member Question

Mark,

The photo attached shows a stain in the marble, my client used stone poultice to pull out the stain, then sealed the tile. Everything was fine until she took a shower for the first time, and the stain reappeared. What are your thoughts?

 

 

 

 

 

 

 

 

Mark’s Response

Thank you for contacting the National Tile Contractors Association.
It appears to me the stain (or darkening) may possibly be caused by water pooling beneath the tile in a potential low spot formed in that section of the shower pan.  Do you know if the darkening of the stone lightens with time / as it dries out?  It may or may not be a possibility that the initial removing of the “stain” by application of a poultice may have been coincidental to the stone simply drying out (i.e. from mortar curing under the stone).
I have attached a copy of the NTCA’s Mesh Backed Stone and Tile white paper.  This may shed some more light on the issue with this installation.
Many sealers protect the molecular structure of the tile from staining but do not keep water from passing into the stone and potentially darkening it. To learn more about how sealers work, here is a link to a complete listing of NTCA’s archived webinars.  https://www.tile-assn.com/?page=webinars
Please view the webinars I’ve listed below for more information on how sealers work and other relevant information:
I hope this helps.
Mark Heinlein
Technical Training Director

TECH TIP TUESDAY: ASK MARK – 11/21/17

Contractor Member Question

Mark,

Is there a way to determine what a stain on the surface of a tile is? We run into this problem every once in awhile.  I currently have a job that has been complete for a few months and they have sent pictures claiming the spots are thinset, membrane or grout.  I do not believe they are any of those things. Is there a way to tell? Please advise.

Mark’s Response

A recognized tile consultant either owns, or has access to laboratory technology that can test deposits on the surface of tiles.
A list of NTCA’s recognized consultants can be found on the NTCA website at this link:  http://www.tile-assn.com/?page=recconsultants
Any of the consultants listed on this page should be able to assist you.
I hope this helps.
Mark Heinlein
Technical Training Director

Ask the Experts – November 2017

QUESTION

I want to install porcelain tile in my kitchen and my condo association requires a 1/4” cork underlayment for sound mitigation, but my installer and everyone else I’ve spoken with tells me I shouldn’t use cork in a wet area. One installer told me that the NTCA does not recognize 1/4” cork as a suitable substrate for tile applications. Can you tell me if that’s true and, if so, is there some documentation about this that I can present to my condo association?

ANSWER

In the NTCA Reference Manual, cork is listed as a questionable substrate for tile. There are several other bonded sound-reduction membranes that are designed specifically for tile installations. Bonded sound reduction membranes may be trowel-applied, sheet, or composite membranes that are bonded to a suitable substrate so that tile can be bonded directly to the membrane. Their purpose is to reduce floor impact noise.

Material specifications for these products are contained in ANSI 118.13. I suggest finding a substitute for the cork that meets ANSI 118.13. Take the technical data from that product and present it to your condo association for approval. I hope this helps.

Robb Roderick,
NTCA Technical Trainer/Presenter

QUESTION

Can you please tell me what the tolerance for lippage for 6”x 36” plank tile would be? The builder is quoting 1/8” which they said is the thickness of two quarters. The tile seems good the long way but the short way – walking across in your bare feet – you feel it.

ANSWER

The American National Standard Specification for the Installation of Ceramic Tile (ANSI A108) defines acceptable lippage for Pressed Floor and Porcelain Tile that meets the specifications for ceramic tile (found in ANSI A137.1) for typical installations of tile to be as follows:

  • All sizes of Pressed Floor and Porcelain Tiles with grout joint widths of 1/16” wide to less than 1/4” wide: Allowable lippage is 1/32”.
  • All sizes of Pressed Floor and Porcelain Tiles with grout joint widths of 1/4” wide or greater: Allowable lippage is 1/16”.

For reference: 1/32” is roughly the thickness of a credit card. 1/16” is roughly the thickness of one penny.

The plank tile you describe is very likely a Pressed Floor and Porcelain Tile. The manufacturer of the tile can tell you whether it was manufactured to the specifications in ANSI A137.1 (it is usually printed on the carton).

I would be happy to discuss any questions your builder or tile installation contractor may have about lippage or other installation standards that can have an effect on lippage.

Mark Heinlein – CTI #1112,
NTCA Training Director;
Technical Trainer / Presenter

QUESTION

Does a shower pan membrane need to be a solid, continuous piece, or is it all right if one corner is completely sliced up and then caulk applied to all cracks? It seems unsafe, and the weight of the concrete and tile could break open all of the cuts. Please help. Thank you very much.

ANSWER

It sounds like you are having a traditional mortar bed type installation constructed that utilizes a waterproofing liner over a pre-sloped pitch.

It is critical to install this, or any type of waterproofing system, in a manner consistent with tile industry methods and standards and manufacturer’s instructions. Rips, tears, cuts, punctures and improperly-sealed seams lead to leaks and failures of the system. With any type of shower installation, I recommend conducting a water test of the system before mortar is placed. In many locales, this is a code requirement placed on the plumbing permit.

The proper methods and details to construct this and many other type of shower pan installations can be found in the TCNA Handbook. If your contractor is a member of the National Tile Contractors Association they will have a copy of this handbook and know how to use it. They should also have a copy of the ANSI A108 standards that provide detailed instructions for the requirements of mud bed installations.

I will be happy to speak to your installation contractor to help them with any questions they may have about this or any other installation. Please feel free to have them contact me. If they are an NTCA member, they are familiar with this service we provide our members. If they are not a member, I would be happy to discuss with them the many benefits of membership including technical support, free training opportunities and obtaining and using the industry standards to base their installations on.

I hope this helps!

Mark Heinlein – CTI #1112,
NTCA Training Director;
Technical Trainer/Presenter

October 2017: TileLetter – Ask the Experts

QUESTION
I have a floor installation with a relative humidity reading of over 90%. Can you advise me of steps I might take to prevent a failure in this installation?

ANSWER
This is a very high reading and beyond the capabilities of most setting materials. In general, most setting products perform well with readings of 3 lbs/1,000 sq. ft./24 hours in calcium chloride test, or readings less than 75% using a relative humidity test. The effect of moisture on floor covering is a huge problem across the United States. Not addressing this issue with a moisture mitigation system will affect the longevity and performance of this installation and probably lead to some type of failure. Some manufacturers have moisture mitigation systems that include waterproofing membrane, and specific thinset mortars that are warrantable up to 12 lbs/1,000 sq. ft. and above 90% relative humidity. My advice to you is to use a moisture mitigation system and the appropriate setting materials that can handle that level of moisture.

There are thousands of setting products that are affected by differing amounts of moisture in a variety of ways. Using the information you have received from a relative humidity test in concert with technical data from your setting material provider is paramount for a successful installation.
– Robb Roderick,
NTCA technical trainer/presenter

 

QUESTION
I was helping a friend with a concrete shower base install and ran into a problem. We poured the concrete base with the required portland cement/sand mixture at the correct slope. About a month after the tile install, the grout started chipping out. After regrouting it continued to fall apart. We pulled up the tile and it came up pretty easy. It’s been about five days now and the concrete still looks wet. I cleared out the area around the drain to make sure the weep holes were clear and they were. Why is the base still wet? I’m hesitant to install new tile on top until it’s dry. Help please!

ANSWER
Can you tell me if a pre-slope of a 1/4” per 12” was installed first then a liner placed over the preslope and sealed to the clamping ring drain, then the mud pack over that? Or, was a surface-applied waterproofing membrane installed on top of the sloped dry pack mud bed and sealed via the divot method to the clamping ring drain? If not, the mud pan is going to hold water if there is no membrane channeling it to the drain system.

Showers and pans are complex systems that must be installed properly to protect the rest of the structure they are installed in. I strongly suggest hiring a qualified professional to perform this installation. The NTCA is the world’s largest association of tile contractors. You can locate an NTCA Member contractor and a Certified Tile Installer in your area by visiting the following sites: www.tile-assn.com or www.ceramictilefoundation.org.

– Mark Heinlein,
NTCA technical trainer/presenter

RESPONSE

Thanks for the quick reply. It looks like I did all of the correct things outlined in your email with exception of the divot method. Now after reading up on the divot method I have questions. Does it require a drastic slope to the drain as shown in the picture below? Also does this method call for a paint-on membrane to be put on the very top? Let me know and thanks again for your time.

ANSWER

Either a liner on the pre-slope or a surface-applied membrane must be used. Not both. Whichever one is used, it must be properly sealed to the clamping ring drain. The divot allows for using a surface-applied membrane in lieu of a pre-slope and a liner with a clamping-ring drain system. Or, a bonding-flange drain system can be utilized to accommodate a surface-applied membrane.

There are many variables, techniques, best practices and standards that must be considered, applied and performed correctly in every tile installation. Showers and wet areas are especially critical. I suggest contacting a qualified, certified, knowledgeable, experienced professional using the links I sent previously. – M.H.

RESPONSE

Mark, thank you. I did the liner on the pre-slope so I should be okay. I just wasn’t sure why the base retained so much moisture even with the liner, slope, and weep holes all in working order.

ANSWER

Drainage issues could potentially be related to the site mix/recipe or consistency of the mix, method of application, etc. Perhaps the problem with the grout could be related to the type and mixing and application of grout or the type and mixing of the mortar and troweling technique used to bond the tile to the mud pack. – M.H.

 

Tech Tip Tuesday: Q & A With NTCA Training Director Mark Heinlein – 10/31/2017

Consumer Question:

Hello! I’m trying to find out if there is an industry standard for the conversion rate of m to kg for Porcelain tiles based on thickness and if so, where I would be able to find this information. Thank you in advance for your assistance.

Mark’s Response:

Thank you for contacting the National Tile Contractors Association.

The Tile Council of North America (TCNA) Handbook for Ceramic, Glass and Stone Tile Installation contains an Appendix (B) discussing “Estimated Weights for Floor Installations.”

This appendix provides a discussion of assumptions for dead load weights of ceramic and stone tile and related setting materials. The assumptions are given in terms of imperial / US Customary (pounds per square foot) measurement vice metric (kilograms per square meters).  Several tables giving the weight calculations for methods included in the handbook are provided in Appendix B.

If you do not own the TCNA Handbook, a copy can be purchased from the NTCA’s Online Store under the Industry Technical Manuals section at this link:  https://tile-assn.site-ym.com/store/default.aspx?

I hope this helps.

 

Mark Heinlein

NTCA Training Director

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