Archive through June 02, 2006

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Author Message Nathan Woods, CCCA Senior Member Username: nwoods Post Number: 94 Registered: 08-2005 Posted on Wednesday, May 31, 2006 - 01:24 pm:    I did a search of the archives, and to my gentle astonishment, this does not seem to be a past topic of discussion... For the past 5 years or more, I have been under the impression that it was improper to use greenboard as a tile substrate for walls in restroom areas such as showers, bathtubs, etc... That we were to use a cementitious tile backer board instead. I was researching USG's new product "Aqua-Tough" and in the process I challenged myself to figure out where or why it states that greenboard was not acceptable. Everything I can find says that greenboard CAN still be used. The TCA (assembly B413), the Gypsum Association, USG, etc... So why have the majority of my contractors, clients, and internal design standards trended away from greenboard in favor of tile backer board? Is it just a precaution against mold issues? Is there a specific guideline or recommendation that you can point me towards? Ralph Liebing, RA, CSI Senior Member Username: rliebing Post Number: 388 Registered: 02-2003 Posted on Wednesday, May 31, 2006 - 01:33 pm:    This from a master specs source-- does it help? Cementitious backer units are an alternative to water-resistant gypsum board for walls over bathtubs, shower receptors, and similar areas where optimum water resistance is required and, for cost or other reasons, a panel material is preferred instead of a portland cement mortar bed. Specifications for cementitious backer units are found in ANSI A118.9 and their installation is specified in ANSI A108.11. Among the advantages that cementitious backer units offer over water-resistant gypsum board is that their cut edges and penetrations do not require treatment with a water-resistant adhesive or sealant to prevent deterioration of the backing. TCA's Handbook for Ceramic Tile Installation recommends a maximum stud spacing of 16 inches (400 mm) with cementitious backer units and, if metal studs are used, a minimum metal thickness of 0.039 inch (1.0 mm). Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 224 Registered: 05-2003 Posted on Wednesday, May 31, 2006 - 02:13 pm:    Check the limitations clause by USG in their current manual: http://www.usg.com/navigate.do?resource=/USG_Marketing_Content/usg.com/web_files/products/prod_details/SHEETROCK_Brand_Water-Resistant_Firecode_C_Core_Gypsum_Panels.htm Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 343 Registered: 07-2002 Posted on Wednesday, May 31, 2006 - 02:20 pm:    I would say that the reason greenboard isn't recommended is that there are so much better products on the market now. Greenboard has a somewhat water resistant face (the green paper) and the edges are treated to not absorb water -- for 6 to 9 inches or so. if the edges are cut, if there is a puncture in the paper, or the paper is peeled off, then you have just regular wall board that deteriorates when wet. the other products may wick water, or hold water in them, but they don't turn to mush no matter how saturated they are. I haven't used greenboard in at least a dozen years. I consider it an old material that has been outmoded, much like the caulking that used to be common when my career started (and I worked with an architect who used to specify oakum on her buildings...) Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 225 Registered: 05-2003 Posted on Wednesday, May 31, 2006 - 02:20 pm:    There is also an excellent article published in the Sun Sentinel (Ft. Lauderdale)on 4/19/2002 in Section E (page 1E & 5E) of the newspaper - the article was entitled "Tile Time Bomb"...regarding the results of green board use in wet areas over time. We only have a hard copy of the article, clipped from the paper in our archives. George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 165 Registered: 11-2004 Posted on Wednesday, May 31, 2006 - 02:22 pm:    The fact is that greenboard never has been able to stand up to the exposure to water that happens when ceramic tile joints fail. Didn't it used to be called M-R (moisture resistant) and not even water resistant? For a while, I've been hearing the rumor that greenboard will no longer be manufactured at some point in the near future, in favor of paperless products. Has anyone else heard this from their gypsum board product reps? William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 600 Registered: 10-2002 Posted on Wednesday, May 31, 2006 - 02:24 pm:    Nathan, besides the limitations noted, basically green board does not do a very good job at what it was supposed to do. It never did. Then along came the cement boards and those are fine, much better at doing what they are supposed to do. Unfortunately, though they are not damaged by water, once wet, they tend to stay wet for a long time...what's to dry them out? Additionally, they are not easy to work (cutting) and they are not friendly to their space (abrasive dust that can destroy fine finishes on tubs, and other plumbing items. I am surprised that no one has mentioned the Dens Shield product which is superior to the cement boards. William (yes, green board used to be called M-R Board, it is officially only "moisture resistant") George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 166 Registered: 11-2004 Posted on Wednesday, May 31, 2006 - 02:32 pm:    William- I have been specifying Dens Shield with cement board as a contractor's option. My perception (which goes back a few years) is that Dens Shield has a higher product cost than cement board, but that cost may be offset by the user friendly features you mention. Most projects thus specified seem to go Dens rather than cement board. William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 601 Registered: 10-2002 Posted on Wednesday, May 31, 2006 - 02:35 pm:    George, For several years, I used to do the same, contractor's opotion to use cement board or Dens Sheild. But they never used cement board, so I stopped offering the option some time ago now and have still never heard a grumble from anyone, not even a VE proposal. Even on larger tile projects where more would be used. Even though more expensive, the larger the project, the ease of installation starts to outweigh the lower cost of cement board. John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 527 Registered: 03-2002 Posted on Wednesday, May 31, 2006 - 03:44 pm:    Actually, green board usually does have a water repellant integral to the core in addition to a repellant facer, but I agree with the comments noted above. I'm not sure that the drying of cementitious backer is any slower than it would be with gypsum--it all depends on the moisture drive of the assembly of which it is part. Another note that most of you are no doubt aware is that green board can't be used on ceilings, one place where I'd really want something water resistant. William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 603 Registered: 10-2002 Posted on Wednesday, May 31, 2006 - 03:46 pm:    John, The Dens type products are not just 'gypsum' products. Take a piece, break it, drop it into water. Take it out a couple months from now and you should notice virtually no saturation at all, even on the broken edges. What does not saurate, does not need to dry out. William Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 226 Registered: 05-2003 Posted on Wednesday, May 31, 2006 - 04:04 pm:    Ok, I learned something today, so John why can MR Board not be used on ceilings? Nathan Woods, CCCA Senior Member Username: nwoods Post Number: 95 Registered: 08-2005 Posted on Wednesday, May 31, 2006 - 04:28 pm:    ANSI AN-3.5.3.1 "Gypsum wallboard (ASTM C-36) and water resistant gypsum backing board shall not be used on ceilings or in critical exposure areas such as exteriors, showers, saunas, or steam rooms. John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 528 Registered: 03-2002 Posted on Thursday, June 01, 2006 - 08:42 am:    The manufacturers themselves state that MR board should not be used on ceilings, wet or not. It's been a while since I asked one of them the reason, but I think it's because it can sag. Dave Metzger Senior Member Username: davemetzger Post Number: 165 Registered: 07-2001 Posted on Thursday, June 01, 2006 - 11:10 am:    On the rare occasions when we have specified greenboard for ceilings, we also specify that the hat channels (to which the board is screwed) be spaced 12 inches oc. This is per the Gypsum Association. The board is heavier than regular gypsum because of the treated core, and as John noted, can sag unless the supports are spaced more closely than usual. Ken Moore, FCSI, CCS, SCIP New member Username: kjmoore Post Number: 1 Registered: 06-2006 Posted on Friday, June 02, 2006 - 04:37 pm:    A little over a year ago, while updating my Office Master, I was told MR board would not be available in 2006, this has not happened. It is still available, but in Chicago Land not very much is being sold. Following is edit note I have in my office master. ****************************************** Insert Specifier’s Note: Verify with code officials if following product [moisture resistant gypsum board] is allowed. ICC International Residental Code “R702.4.2" restricts use of this product “as backers of wall tile in tub and shower area and wall panels in shower areas” ICC International Building Code (IBC) presently has not adopted this restriction for commercial construction projects. ****************************************** I have, for decades, specified "GP's Dens-Shield Tile Guard" for tile backer board. At one time it was 1/2 the price of Cement Board, that is no longer the case. Dens-Shield Tile Guard is now about same cost as Cement Board. But glass mat board is less labor intensive to install. For ceiling in showers, subject to water splash, I specifiy Dens-Shield Tile Guard and apply a skim coat of Sto, Dryvit, Synergy or Parex finish coat. See GP data sheet for details. For interior high humid areas, such as change area outside gang showers, and stand alone seasonly facilities such as pool rest rooms, conncession area and other facilities that are seaonal and are not conditioned year round, I specify " DensArmor Plus Interior Guard". It has tapered edges, so can be taped and give a smooth even appearance. Most other G-P glass mat products have square edges so you have to tape and apply a skim coat to hide joint. [example soffits] Note: G-P revised their trade names about 1-1/2 or 2 years ago. Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 131 Registered: 10-2002 Posted on Friday, June 02, 2006 - 05:39 pm:    Is there an "official" definition of "wet wall" somewhere? All walls receiving tile should not be considered a wet wall. The obvious definition would be showers, slopsink walls, etc. But, in my opinion, a toilet room wall with a decorative tile finish should not be considered wet - unless or course there is a urinal located on it. <g> What about a straight tiled wall that is partly a shower stall? Can it be two different substrates with satisfactory results? Ron Margaret G. Chewning FCSI CCS Senior Member Username: presbspec Post Number: 100 Registered: 01-2003 Posted on Friday, June 02, 2006 - 05:53 pm:    I haven't done this in quite a while, but remember requiring a tile backer board or moisture resistant board within and up to 2 feet of a water source, (ie tub, shower, slop sink, faucet) designating it the wet zone, whether there was tile or not. These days I'd use the green board out side the wet zone with the tile backer board (Dens-sheild or what ever) in the wet zone. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 345 Registered: 07-2002 Posted on Friday, June 02, 2006 - 06:08 pm:    the biggest issue with two different substrates (as in your partly shower stall wall) is that the cement board is typically 1/2" thick and type X wallboard is 5/8" thick. if you were to continue tile along both substrates, then you would have to shim one or use the 5/8" version of cement board, or the 1/2" version of wallboard. in our area, the material cost is usually less than the fussing-around-labor cost to switch boards in the middle of a wall. we would typically run the cement board to the corner unless there were some other natural break in the wall plane. In toilet rooms its not unusual for us to just use cement board for the whole room if it has tile on it. there is always the weird possibility that one of the fixtures will flood or there will be some other circumstance that has the room flooded with an inch or so of water, and of course it happens on the three day weekend. our definition of "wet wall" is any wall -- the whole length -- that has a plumbing fixture installed on it. Ronald L. Geren, RA, CSI, CCS, CCCA, MAI Senior Member Username: specman Post Number: 271 Registered: 03-2003 Posted on Friday, June 02, 2006 - 06:10 pm:    Just an intersting side note... The 2003 IBC limited base material for tile in showers and tubs to "water-resistant gypsum backing board"; there is no provision for cementitious tile backer panels (I guess, technically, you would have to submit a code modification for alternate material). It also limits ceiling use to 12" frame spacing for 1/2" WR gypsum board, and 16" spacing for 5/8" WR gypsum board. However, the ICC wised up, and in their 2006 IBC, they've replaced water-resistant gypsum board with "cement, fiber-cement or glass mat gypsum backers" for showers and tubs, and limit WR gypsum board as a tile backer for only water closet compartments. The same ceiling limitations apply; however, in showers and tubs, WR gypsum board is not permitted, only the three materials listed can be used. Nathan Woods, CCCA Senior Member Username: nwoods Post Number: 96 Registered: 08-2005 Posted on Friday, June 02, 2006 - 06:13 pm:    Ron, that's great info. What is the IBC section reference? Ronald L. Geren, RA, CSI, CCS, CCCA, MAI Senior Member Username: specman Post Number: 272 Registered: 03-2003 Posted on Friday, June 02, 2006 - 06:14 pm:    Section 2509, both editions. Ronald L. Geren, RA, CSI, CCS, CCCA, MAI Senior Member Username: specman Post Number: 273 Registered: 03-2003 Posted on Friday, June 02, 2006 - 06:27 pm:    Anne: Both Durock (USG) and PermaBase (National Gypsum) have 5/8"-thick products. George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 169 Registered: 11-2004 Posted on Friday, June 02, 2006 - 06:48 pm:    "Wet walls": If memory serves, HUD's now obsolete Minimum Property Standards required M-R board "in bathrooms and on all wet walls", which their inspectors and reviewers defined as "anything with a water pipe coming through it". That meant the kitchen sink wall, and the washer/dryer wall, but not the other walls in those rooms. It also meant only the plumbing wall in a half bath (no tub/shower). Full baths got M-R board on all walls. This goes back thirty years or so, when all there was, was greenboard. Unlike IBC today, I doubt the building codes mentioned it at all. Of course, good architectural practice called for us to use at least MPS requirements on private residential projects as well. I think as we trend to paperless gypsum board, traditional M-R board will vanish, and there will be a (if there isn't already) a Dens-"something" glass-mat product that will work as a tile backer and will be able to be finished like gypsum board. Same board for tile or paint, stop the tile where ever you wish.