How to remove stains from pavers


I have a client with peacock pavers. They had a large mat in front of their door with two planters on either side if it. The planters leaked onto the mat and drained off the porch, but the dye from the mat has left a bad stain on the pavers. Any recommendations on how to pull those stains out?


2019-20 NTCA Reference Manual

I would contact a company that makes sealers, grouts, and related products and ask them if they have a product that will work to dissolve the minerals that leached in from the planters. Some setting material manufacturers also make products like these. If you know which company made the grout and/or thin-set, they would be the logical choice to ask first.

Do you have a copy of the NTCA Reference Manual? In the manual, there is a section dedicated to processes to remove stains from tile and stone. A quick browse through the table of contents will point you to this section that will provide tips and tricks that may help remove stains like these.

– Mark Heinlein,
NTCA Technical Director

Is the drywall installer or tile installer responsible for the joints/corners?


We have a project with wall tiles that are 4” x 40”, 8” hex and large 24” x 47-1/8”. The general contractor has drywall figured and states that joints or corners shouldn’t have to be mudded/done by the drywall installer nor primed! Our tile installer said that he wants the joints and corners completed and everything primed before he will install. These areas are not in a wet area. However, the large tile is at a fireplace wall.

What is correct?


TCNA Handbook Methods (l.) W242 and (r.) W243.

There are two recognized methods for installation of tile over gypsum board found in the Tile Council of North America Handbook. They are methods W243 (thin-set) and W242 (organic adhesive). Both have a section of the method that are titled “Preparation by Other Trades”. In that section it states gypsum board shall be installed per GA 216 “treated with tape and joint compound, bedding coat only (no finish coats). Nail heads one coat only.”

To my understanding primer is not needed. We do recommend slightly dampening the surface of the drywall to help ensure the board does not prematurely draw the moisture out of the thin-set bond coat.

– Robb Roderick,
NTCA Technical Trainer


Q: Would you say primer is the responsibility of the tile installer or drywall installer?

A: If we are going to put tile onto the drywall surface and the primer is necessary to prepare the drywall for a successful tile installation, this would be the responsibility of the tile contractor and not the drywall contractor.

Should there be 1/8″ gap when using an uncoupling membrane


We’re going to use an uncoupling membrane on a wood subfloor. I know when it’s a brand new subfloor there should be a 1/8” gap. This house has had the subfloor in place for the past 10 years. Do I still need to cut the 1/8” gap? 


It is a best practice to have the gap in place between the wood (i.e. plywood/osb). Although the wood structure has been in place for 10 years, it has likely expanded or contracted over those years and may do so again. The uncoupling membrane will likely protect from that expansion and contraction but I suggest following the best practice of opening up the gap.

It’s pretty easy to do. Set the depth of a circular saw to about 3/16”-1/4” deep (just deep enough so you don’t cut the wood tongue off) and run the saw down the joints between the sheets. Use a good carbide tipped blade that will give you about a 1/8” kerf or cut width.

For the ends of the runs near the walls, use an oscillating tool to finish opening up the gap.

Mark Heinlein,
NTCA Training Director

Can grout and sealant be mixed together?


Can grout and sealant be mixed together so you don’t have to seal the grout when it’s done?


Sealers are not designed to be mixed with grout. Sealers are designed to be applied to cured cementitious grout. 

There are two basic categories of sealers. They are generally designed to either penetrate the surface of the cured grout (penetrating sealer) or to cure as a sacrificial layer on top of the cured grout (topical sealer).

There are admixtures that are specially formulated and designed to be mixed with cementitious grout. These admixtures are usually designed to replace the need for sealers.

There are a wide variety of grouts available. Some are considered ready-to-use and likely do not require any sealing at all. Some powered grouts are formulated with sealers already in the dry mixture.

I suggest you contact the manufacturer of the grout you are using to determine its properties and whether a sealer is recommended for use with it. 

Mark Heinlein,
NTCA Training Director

Who determines construction joints?


We are on a job won by a flooring contractor who will install sheet vinyl or porcelain tile on a concrete floor. We are trying to determine who identifies where the construction joints are and how they will be treated, if it is not provided in the drawings.


The person with knowledge of the building and structure has to identify where the joints are and how they will be honored or treated depending on the type of joint. 

If there are drawings and specifications for the job, the professional that analyzed the structure to ensure adequacy for a tile installation and who drew up the specifications is the person responsible for providing the tile installation contractor the drawings for location and identification of honoring / treating the structural joints.

You can refer them to TCNA Handbook method EJ-171 where this is further defined. 

Mark Heinlein,
NTCA Training Director

Pressure-treated lumber to build a bench or curb


I’m looking for the spot in the TCNA Handbook that states that you are not allowed to use pressure-treated lumber to build a bench or curbs. Is there any way you can send that to me or tell me what page in the book it is?


In the TCNA Handbook’s shower methods section, under the requirements for wood studs, it states they must be dry and well braced. The general requirements for wall bracing are found in ANSI A108.11 in section 4.1 Wood Framing requirements. It states all framing lumber should have a moisture content not in excess of 19%. Most pressure-treated lumber has moisture content ranges of 30% to 70%. In a tile assembly, pressure-treated wood has a tendency to twist and contort as it starts to dry out. The rigidity of the tile assembly cannot generally handle that type of movement, and can fail from it. Also view page 30, Chapter 2 of the 2018/2019 NTCA Reference Manual for information about questionable and unsuitable substrates. 

Tiling over tile


Is there anywhere besides TR711, TR712, and TR713 that discusses tiling over tile? I’ve looked on the TCNA website, which states that procedures are described “in detail” in those standards. Other than stating the existing installation must be sound, well bonded, and without structural cracks, there aren’t any real details. Are there differences between a concrete substrate and a wood subfloor? Do I have to determine HOW the previous installation is adhered and how much it weighs? What other things may I need to take into consideration that I wouldn’t otherwise?


The “TR”/Renovation methods in the TCNA Handbook for Ceramic, Glass and Stone Tile Installation are the methods that discuss tiling over an existing tile installation.

In addition, the 2018/2019 edition of the NTCA Reference Manual section “Tile Over Other Surfaces” (page 257) includes more information, such as the need to prep the tile surface by scarification or application of specialized primers to promote bond to the existing tile surface.

As you have sensed, it is critical that you thoroughly analyze the components of the existing tile installation to determine whether it was properly installed and whether it will serve as a quality substrate for the new Employee-Handbook-v9 installation you are looking to bond to it. Since all components of the existing installation will become the new substrate, it must be carefully analyzed to determine if it will successfully support the new tile installation. The Substrate Requirements section of the TCNA Handbook (pages 30 – 33 of the 2019 edition) are worth reviewing.

It may be necessary to remove some tiles, bond coat, and any underlayment to ensure they were correctly installed. Sometimes, drilling a series of core samples is a good way to determine the adequacy of the existing installation and how well it will serve as a substrate for your new tile installation.

You (or a structural engineer or similar) must ensure that the structure will be able to support the added weight of the new tile and bond coat over the existing installation. Deflection, live loads, dead loads, etc., are part of the consideration. TCNA Handbook methods for floor installations list the Service Rating for the method. Also refer to the Performance Level Requirement Guide and Selection Table in the 2019 TCNA Handbook (page 43) for more information on Service Ratings.

If the tile over tile is to be done in a wet area, you must take into consideration such factors as the type and condition of the existing waterproofing membrane, whether 95% mortar coverage was achieved in the original installation, etc. You will likely need to apply a new membrane before installing your tile. Doing this will encapsulate the existing tile and bond coat between two layers of membrane. It is important to determine whether adequate bond coat existed in the first installation to ensure no pockets of water or other materials are being trapped between the membrane layers.

As with tiling over any substrate, it is necessary to ensure the substrate meets the flatness requirement for the size of tile you are installing. If the existing installation does not meet the flatness criteria, it must be flattened with the appropriate materials first. Your setting material manufacturer can assist you with the correct materials (possibly including primers) and techniques to correct unflat substrates.

In summary, everything about the existing substrate and substructure must be considered before tiling over an existing tile installation. 

Should I grout the old fashioned way with mud cement?


I am looking for an opinion. I have installed a 4˝x8˝ porcelain outdoors with thinset with 1/4˝ joint. I wanted to grout the old fashioned way with our mud cement – with extra Portland – cleaned with sawdust. I feel that the joints were full years ago. Thank you so much, I look forward to your opinion.


While the system of grout you described may work well, depending on your ratio of materials, many of the modern grouts available today have been engineered to stand up to harsh climates and use.

Reading and following manufacturers’ instructions carefully, along with a little practice, will produce full joints and great results with today’s materials. I suggest checking with the setting material company that makes the thinset you’ll be using for their suggestions of grout for your installation.

Regardless which grout system you use, an exterior installation has many critical elements that must be addressed. Please refer to the Tile Council of North America Handbook For Ceramic, Glass and Stone Tile Installation for the appropriate method, details and materials for this installation. 

Should this be a demo or can I replace the shower pan?


I have a customer that has a shower stall they would like updated…a little. New custom glass enclosure, new fixtures, and…a new pan? The two walls of the shower are white quartzite. She is in love with it and does NOT want to remove it. However, the pan is fiberglass. She does not like it and it has stains that won’t go away. She would like to have some kind of stone or tile to replace the pan.

My questions: 

  1. Will I be able to make a pan that won’t fail in years to come?  
  2. I would expect that the fiberglass pan has a flange that wraps up behind the slabs of quartzite. If so, how do I address that


Thanks for getting in touch with us about this problem. Let me address your questions first:

1. Many shower pans have been made from tile and related components that, when properly constructed, last for a very long time. There are many methods to construct such a pan. Have you built a shower pan before? Which method or system do you use or are you familiar with?

2. You are correct that the existing pan likely has a lip that extends behind the first course of tile and possibly behind the substrate. As your question suggests, it would likely not be an easy or simple task to remove the band of the quartzite, patch or install the waterproofing membrane that may or may not be behind it, and replace the membrane and the quartzite and the pan with a new tile system that you will be comfortable with installing and selling to the owner as a functional system that will stand the test of time.

I suggest you determine the best method and system approach that you are comfortable with, and then discuss with the owner the reasons why it makes much more sense to demo, replace and upgrade the entire shower.

I look forward to hearing back from you so I can help guide you on the best way to continue. 

If a shower floor slope is 1/4″ per foot are other horizontal surfaces also 1/4” per foot?


I have a quick question about how much slope a shower bench or shower dry-off area should have.

The TCNA Handbook states that “All horizontal surfaces, for example shower seats, sills, curbs, etc., must slope towards drain.”

Shower floor slope is 1/4″ per foot. Are the other horizontal surfaces (bench, etc.) also supposed to be 1/4” per foot?


Yes, the correct slope for all horizontal surfaces is 1/4″ vertical (minimum) up to 1/2″ (maximum) for every 12” of horizontal run. 

– Mark Heinlein,
NTCA Training Director

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