June 30, 2015

NTCA Reference Manual: exploring underlayments (April 2015)

NTCA_RMThe NTCA Reference Manual, an essential industry document, explores the subject of underlayments in Chapter 3. This publication is free as part of NTCA membership or can be obtained through the NTCA website at www.tile-assn.com.

The NTCA Reference Manual gives an overview of the types of underlayments one is likely to need or encounter on a tile or stone setting project, as follows:

Factory-prepared powdered underlayments usually fall into one of three categories:

1. Gypsum based
2. Cement-based latex underlayments
3. Cement-based self-leveling underlayments

1-underlayment_article1. Gypsum-based underlayments are predominantly composed of various grades of gypsum, chemicals to control set time, and may be sanded or unsanded. They may be mixed with water or a latex admixture, but are to be used only in dry areas, since gypsum-based materials are highly sensitive to moisture. These materials are normally used by the resilient flooring mechanic for patching small holes, cracks or for correction of thickness variations of adjacent flooring materials. However, larger areas may be leveled with products that require 3/4” minimum thickness over wood and 1/2” over concrete substrates. Gypsum-based underlayments are not recommended for use under ceramic tile or stone.

2. Cement-based latex underlayments are composed of cement, aggregate and are mixed with a latex additive. Most instructions recommend the application of a slurry coat to the substrate made from the powder and the latex additive. This slurry is only allowed to dry to a tacky condition before application of the normal mix. It normally requires sanding after curing to remove trowel marks and for further leveling.

3. Self-leveling underlayments are composed of cement, aggregate and chemical modifiers that increase flowability and strength. Substrates are normally primed with a latex material that serves as a bonding agent and a sealer. Most self-leveling materials may be mixed with water or with latex admixtures.

The NTCA Reference Manual also presents a table of Problem- Cause-Cure parameters for some common problems that arise when using underlayments. Following are the categories of underlayment woes and the problems that contribute to the difficulty.

unapproved_latexesLoss of Underlayment
Bond To Substrate

  • Improper preparation of substrate. Applications of material over dust, dirt, curing compounds, old adhesives, spalled or soft concrete, etc.
  • Deflection of substrate.
  • Failure to prime the substrate according to directions on the product.
  • Diluting latex additives with water.

Cracking

  • Mixing product with too much water or latex.
  • Bridging expansion joints, control joints, or slab cracks.
  • Application of material exceeding thickness restrictions.
  • Over-troweling/overworking surface.
  • Exposure to excessive wind or direct sunlight during initial curing stage.

powdery_underlaymentSoft or Powdery

  • Mixing underlayments with too much water or latex.
  • Mixing with high-speed drill.
  • Diluting latex additives with water.
  • Using gypsum-based materials in areas subject to moisture.
  • Using cememt-based underlayment over gypsum underlayment.
  • Mixing with foreign products or substituting one product for another
  • Moisture penetration followed by freeze/thaw cycles

Poured gypsum underlayments

Also included in the NTCA Reference Manual exploration of underlayments is a section on poured gypsum underlayments. They have distinctive properties, characteristics, and capabilities that are presented as follows:

poured_underlaymentPoured gypsum underlayments can provide a satisfactory surface to receive ceramic tile installation systems. These floors are available in compressive strengths of 1,000 to over 8,000 PSI. It is recommended that the tile installer verify that the poured floors meet a minimum compressive strength of 2,000 PSI and a minimum density of 115 lbs. per cu. ft. when tested in accordance with ASTM

C472. Poured gypsum underlayments are suitable for interior substrates only, above grade, and in areas not subject to constant water exposure or immersion.

There are currently four approved methods the TCNA Handbook uses for poured gypsum underlayments in tile installations.

F200 – Poured Gypsum over Concrete

F180 – Poured Gypsum Underlayment over Plywood

RH111 – Poured Gypsum over Concrete with Hydronic Heat

RH122 – Poured Gypsum over Wood with Hydronic Heat

Drying of the gypsum underlayment

Poured gypsum floors are made with a job site mixture of powder and water and require time to dry before they can be primed/sealed and tiled. Verification that the gypsum underlayment is dry can be determined in accordance with ASTM D4263: Plastic Sheet Method. This test process shall be performed by the gypsum installer, prior to the application of any primers/sealers. Do not proceed with the tile installation until the poured gypsum is deemed dry and has been primed/sealed.

As a general guideline, the following drying times should be observed prior to testing the surface for dryness.

Thickness of poured gypsum and dry time before testing:

1/4”      48 hours

1/2”      72 hours

3/4”      5 days

1”      7 days

2”      2 weeks

Preparation of the poured gypsum surface

In general, ceramic tile is not bonded directly to gypsum underlayments. While each manufacturer of these materials has their own specific requirements, the use of a primer/sealer or a primer and membrane is required. Any exceptions to this recommendation are proprietary in nature and suitability rests solely with the gypsum manufacturer.

Primer/Sealer

Some gypsum manufacturers recommend the use of a primer/sealer over the surface of the dry gypsum before installing any membrane or setting material directly. Also referred to by some as a “sealer” or “overspray,” the use of these primers is intended to prevent the gypsum from absorbing water from the setting material, which can result in poor adhesion. Please note that while you may not have installed the poured gypsum, you must verify that the primer/sealer was applied in accordance with the manufacturer’s recommendations, after the gypsum floor was deemed dry.

Membranes

The Tile Council of North America and some gypsum manufacturers recommend the use of membranes in addition to the primer prior to installing the tile over their poured underlayments. For the purposes of these applications, membrane is as defined by ANSI A118.12 for crack isolation or ANSI A118.10. Check with the manufacturer for their individual requirements.

NOTE: The tile contractor shall obtain written documentation verifying that the poured gypsum floors have met or exceeded the minimum compressive strength of 2,000 psi and minimum density requirements of 115 lbs. per cu. ft. per ASTM C472, has been tested per ASTM D4263 and deemed to be dry, and has been primed/sealed in accordance with the manufacturer’s recommendation. This information shall be provided to the tile contractor by the general contractor, owner, builder or certified poured gypsum installer.

NOTE: The requirements of this document exclude patching compounds.

POSITION STATEMENT ON THIN PORCELAIN TILE

 

 

The NTCA, along with other leading tile installation trade associations, has released a position statement on thin porcelain tile. For more information on this statement, contact Bart Bettiga, NTCA executive director. ACT_Position_Statement_Thin_Tile

Schluter-Systems hosts training and educational seminar for NTCA members

bart_0114By Bart Bettiga

Schluter-Systems’ new LEED Gold certified building is located just outside Reno, Nevada, and offers a picturesque view of mountain ranges on the horizon surrounded by terrain adjacent to the property with running streams and wild horses roaming freely on the land. In addition to the state-of-the-art facility, Schluter’s 97,500-sq.-ft. building is strategically located to offer increased service and faster delivery of products for their west coast distributors, dealers and contractors. It is also an ideal location for training and educational programs. The facility features a multitude of sensible and sustainable technologies to maximize energy efficiency, water usage and air quality.

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The Schluter Reno building used thousands of square feet of tile in both interior and exterior applications, and acted as a virtual hands-on research and development project.

Schluter recently hosted over 75 NTCA members for a training and educational seminar and tour of the facility. This was also an excellent opportunity for NTCA staff to update the attendees on association direction and strategic planning. The program included a complete presentation and tour of the building, which was in essence a hands-on research and development project for Schluter. Many of their products are showcased throughout the facility, offering a great example of how conventional building methods continue to evolve, and how tile and stone can be key elements in the successful implementation of sustainable systems that maximize energy efficiency.

schluter-sidebarAndy Acker, a leading trainer and presenter for Schluter-Systems, was the lead speaker and facilitator of the program, which consisted of two complete days of highly-engaged interaction. Former NTCA regional director and contractor John Trent, who is currently employed with Schluter, was instrumental in putting the program together and assisting in its development and promotion.

Topics discussed in the first day of the training seminar included lengthy interaction on the principle of uncoupling, covering details from the TCNA Handbook and thin-set installations. New product introductions included a preview of the new Ditra-Heat system, which was recently introduced to the trade. NTCA and Schluter leaders then held an open-forum discussion on installation practices and business strategies before heading out to a fabulous dinner.

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Dee DeGoyer of Schluter-Systems was the tour presenter and explained the detailed planning that went into the state-of-the-art facility.

Day Two consisted of the NTCA strategic planning update and a Schluter presentation on moisture management, including a lengthy discussion of waterproofing and examining details of both the TCNA and Schluter installation handbooks. Presentations on Schluter Kerdi Board and their innovative profiles as solutions to challenging installations completed the morning sessions. After lunch, all of the attendees broke into groups and moved into the training center locations, where several territory managers were ready with demonstrations of products in carefully-constructed modules. All of the groups had time to see the hands-on training demonstrations, ask questions and make comments, and move on to the next module.

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One of the highlights of the seminar included round -robin presentations in small groups of Schluter pw2ju22XZ(922fgroducts and systems.

The educational portion of the event concluded with presentations by Schluter leaders offering a glimpse into the future, sharing some strategies of products currently being considered for development. Schluter also shared their position on supporting Certification through the CTEF programs, and pledged to support the ACT Certifications currently being offered.

Many of the attendees stayed an additional day to go skiing, snowboarding and snowmobiling in the beautiful mountains located near Lake Tahoe. By all accounts, those that stayed the extra day were treated to a memorable experience. Schluter-Systems and NTCA leaders agreed that future meetings of this nature would continue to provide value to our members.

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New products demonstrated at the seminar included the Ditra-Heat system, which will be on display at Coverings.

 

 

 

 

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Several attendees took the extra day offered by Schluter to enjoy the winter climate with skiing, snowboarding and snowmobiling adventures.

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Over 75 NTCA members attended the training seminar at the recently completed Schluter-Systems LEED Gold Certified building in Reno, Nevada.

 

Installing ceramic tile, glass tile and stone interior wet areas

By Donato Pompo, CTC CSI CDT MBA, Ceramic Tile and Stone Consultants (CTaSC), University of Ceramic Tile and Stone (UofCTS).

(Editor note: a condensed version of this story appears in the January 2014 issue of TileLetter)

 Exterior decks and balconies, and interior showers and bathrooms have historically been problematic areas for the installation of ceramic tile, glass tile, stone tile and other stone products.   Typically problems are due to installer error, not using appropriate materials for those applications, or not having clear enough specifications.  In each case it is the result of not following industry standards.

 

Importance of industry standards

Industry standards are created by industry consensus groups consisting of installers, producers, and industry experts through organizations such as ANSI (American National Standards Institute), TCNA (Tile Council of North America), ASTM (America Society for Testing and Materials) or ICC (International Code Council).  These consensus-group members combine their many years of experience with science to establish standards so problems and failures can be avoided and not repeated.  Thus if standards are not followed then known potential problems can’t be avoided.

 

Excessive moisture:

culprit in tile and stone failures

In the last ten years or so, since the demand and use of tile and natural stone has grown so dramatically, there have been a lot more failures caused by tile and stone being subjected to excessive moisture.  Obviously tile and stone are very resistant to problems as indicated by the fact that there are tile and stone installations that are still standing and functional after thousands of years of use and exposure to various weathering conditions.

But when a number of things are done incorrectly in a tile and stone installation, particularly where water is involved, it can lead to extreme damages that can cause visually aesthetic damages and substantial collateral damages of adjacent materials, which can significantly reduce the functional life of the tile or stone application.

On the other hand, if tile and stone are installed correctly, per industry standards and product manufacturer’s directions, these products can provide trouble-free installations that can provide many years of pleasing aesthetics and successful performance that will be our legacy to future generations.

In over 11 years as a forensic investigator, I have found the common denominators to failed exterior decks and balconies, interior showers and bathrooms are the lack of proper slope, plugged weep holes, and inadequate flashing to contain or manage the water , resulting in various types of damages.

First, consider that exterior decks and balconies are often not only subjected to water directly from rain, but often water is channeled through drains and scuppers to these areas further subjecting them to higher volumes of water.  Plus these areas are often washed down regularly so they are further subjected to large volumes of water.

Consider the volume of water that showers are subjected to annually.  If one person takes a 12-minute shower each day in an average size shower with reasonable water pressure and using an appropriate shower head, the amount of water it is subjected to is equivalent to a roof being subjected to about 1,000 inches of rain water per year.  Since these areas are likely to be subjected to more water than a typical roof is subjected to annually, it is imperative that extra care and attention is spent on specifying and constructing them. This is accomplished by properly managing the water so it is controlled and safely evacuated from those areas.

 

 Be savvy about slope

Lack of adequate slope is a common problem in both exterior horizontal applications as well as interior wet horizontal applications such as shower floors, shelves and seats.  It is very clear in the tile and stone industry standards, as well as in the Uniform Plumbing Code (UPC), and in the IRC (International Residential Code) or IBC (International Building Code) building codes, that the slope to drain, or away from the building, should be a minimum 2% slope.  That calculates to 1/4″ per foot (6 mm per 305 mm).  UPC says the slope to drain in a shower must be a minimum of 1/4″ per foot (6 mm per 305 mm), but not more than 1/2″ per foot (13 mm per 305 mm).

Not only is it important for that slope to drain to be at the surface of the tile or stone, but it is critical that the minimum 1/4″ per foot (6 mm per 305 mm) slope to drain is at the surface of the waterproof membrane.

Drains come in two sections.  Where the drain clamps down on the waterproof membrane — below the surface of the tile assembly — there are weep holes in the drain assembly, so that any water that migrates to the waterproof membrane can then evacuate into the drain through the weep holes.

One of three common problems that we run into is first that the waterproof membrane is not properly sloped to the drain.  In a shower this can result in the tile mortar bed staying constantly damp, which results in the room taking on a musky odor or it may cause a stone or tile floor to look wet, and the excessive moisture might result in the stone spalling (deteriorating) and/or staining.   Sometimes we find that the waterproof membrane is flat or even negatively sloped away from the drain, or that there are low spots on the membrane surface where water collects.  These same conditions can be found on an exterior deck or balcony.  Obviously an exterior deck or interior commercial floor with multiple drains is a somewhat complex installation for the waterproof installer and the tile installer. In these cases, you will have transition areas that peak and slope in one direction or the other towards the respective drain.  So it is critical to make sure that the drains and slopes are properly laid out to allow for all the water that reaches the membrane to readily evacuate through the drain weep holes.  Even when there are drainage mats installed on top of the waterproof membranes to facilitate the evacuation of water from the mortar bed into the drain, if the waterproof membrane is not properly sloped it can result in expensive problems.