| Author |
Message |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 1281
Registered: 05-2003
| | Posted on Sunday, March 22, 2015 - 09:42 pm: |    |
In a wet wall condition with cement board being applied over wood or metal studs, with WRB in place, is the Cement Board installation considered water resistant or waterproof? I thought this had been discussed previously on the forum, but I could not find it. My apologies if I missed it.
Ceramic tile will be adhered to the cement board in this condition. |
Curt Norton, CSI, CCS
Senior Member
Username: curtn
Post Number: 213
Registered: 06-2002
| | Posted on Monday, March 23, 2015 - 08:28 am: | |
Since the cement board absorbs moisture, it's not waterproof. |
J. Peter Jordan
Senior Member
Username: jpjordan
Post Number: 806
Registered: 05-2004
| | Posted on Monday, March 23, 2015 - 10:00 am: | |
I agree with Curt. When I am using cement board, I use a system like Laticrete LVS (I believe Mapei also offers one) over the cement board which serves as a waterproofing air barrier. The tile is then thinset to the air barrier. |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 1282
Registered: 05-2003
| | Posted on Monday, March 23, 2015 - 10:28 am: | |
Perhaps what I need is a definition of water resistant versus waterproof. I reviewed a clients drawing and there was a note that said to "provide water resistant cement board in all wet wall conditions", I did not know that cement board was water-resistant? I thought it was the assembly? |
Dave Metzger
Senior Member
Username: davemetzger
Post Number: 567
Registered: 07-2001
| | Posted on Monday, March 23, 2015 - 11:55 am: | |
Seems like your client just changed an old "water-resistant gypsum board" (the old green board) note to "water-resistant cement board". As you know, the code no longer allows "water-resistant gypsum board" for use in wet walls (although we have used mold-and moisture-resistant board).
Cement board is what it is, it does not come in water-resistant and regular types. As Peter noted, we specify a troweled-on W/P membrane to be applied to the substrate, below the thinset mortar bed. This membrane should be by the same manufacturer as the mortar. |
Dale Roberts CSI, CCPR, CTC, LEED Green Associate
Senior Member
Username: dale_roberts_csi
Post Number: 118
Registered: 10-2005
| | Posted on Monday, March 23, 2015 - 12:09 pm: | |
There are backer boards (they are not cement boards) that can be used in wet areas like DenShield from GP, GlassRoc from Certain Teed. Schluter Kerdi-Board, Wedi and KBRS. You have to remember with these systems you have penetrations and seams to waterproof. I prefer a cement board that can be used interior or exterior. Cement backer boards (CBU) are not waterproof or water resistant. You will need to use an ANSI A118.10 waterproofing membrane on top. This liquid applied membrane waterproofs all the penetrations and seams. Laticrete has HydroBan, Mapei has AquaDefense. And of Course Custom Building Products can offer you a single source installation system for all your needs, from CBU WonderBoard to RedGard ANSI A 118.10 Liquid applied waterproofing membrane. |
John Bunzick, CCS, CCCA, LEED AP
Senior Member
Username: bunzick
Post Number: 1629
Registered: 03-2002
| | Posted on Monday, March 23, 2015 - 01:40 pm: | |
There are two aspects here. One is the fact that cement board resists deterioration due to moisture quite well, even though it will absorb moisture. From that perspective it can be said to be water resistant; even waterproof in layman's terms. Then there is the sense of something providing a waterproofing or water-resistant effect to something else, such as an assembly that will not allow water to pass through it. Cement board does not do that on its own. To be part of a waterproof assembly, there must be other components to do the job: a membrane, seam treatments, and the like. I think your client's note refers to the requirements of the code, which I believe (without doing research) applies more to the first sense. |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 1285
Registered: 05-2003
| | Posted on Tuesday, March 24, 2015 - 02:21 am: | |
JP, What is Laticrete LVS - not listed on Laticrete website as a product? |
Jerome J. Lazar, RA, CCS, CSI, SCIP
Senior Member
Username: lazarcitec
Post Number: 1286
Registered: 05-2003
| | Posted on Tuesday, March 24, 2015 - 11:46 am: | |
Now the Architect is challenging my spec for requesting a WRB behind the Cement Board where cement board is receiving tile. I've always specified this and thought it was a manufacturer's requirement, but now I can not find the WRB requirement in the cement board warranty? Is the use of WRB behind the Cement Board good practice or a code or manufacturer requirement? |
Curt Norton, CSI, CCS
Senior Member
Username: curtn
Post Number: 214
Registered: 06-2002
| | Posted on Tuesday, March 24, 2015 - 11:51 am: | |
I've never used a WRB, but I've also never specified a shower that needed to be waterproof. if it is just a wet wall in a toilet room, I don't see the need.
When I did the shower walls in my personal bathroom, the cement board sat "mostly" in front of the cast tub lip and I didn't use any waterproofing. It was just screwed to wood studs. That was about 15 years ago, and I haven't seen signs of a leak yet. |
Lynn Javoroski FCSI CCS LEEDŽ AP SCIP Affiliate
Senior Member
Username: lynn_javoroski
Post Number: 1987
Registered: 07-2002
| | Posted on Tuesday, March 24, 2015 - 12:06 pm: | |
I'd consult the TCNA manual and spec a system from that. |
Dale Roberts CSI, CCPR, CTC, LEED Green Associate
Senior Member
Username: dale_roberts_csi
Post Number: 119
Registered: 10-2005
| | Posted on Tuesday, March 24, 2015 - 12:22 pm: | |
TCNA defines a wet area as the surfaces that are soaked, saturated or regularly and frequently subjected to moisture or liquids. Includes areas adjacent to C4 areas. Examples: Tub Walls, shower walls and floors, enclosed pool areas, natatoriums, gang showers and some commercial kitchen floors and walls.
TCNA requires shower receptors to have a waterproof membrane. For most tub walls it is optional. I would highly recommend it.
IPC states
417.4.1 Wall area. The wall area above built-in tubs with installed shower heads and in shower compartments shall be constructed of smooth, noncorrosive and nonabsorbent waterproof
materials to a height not less than 6 feet (1829 mm) above the room floor level, and not less than 70 inches (1778 mm) where measured from the compartment floor at the drain. Such
walls shall form a water-tight joint with each other and with either the tub, receptor or shower floor. 417.5.2 Shower lining. Floors under shower compartments,except where prefabricated receptors have been provided, shallbe lined and made water tight utilizing material complying with Sections 417.5.2.1 through 417.5.2.5. Such liners shall
turn up on all sides at least 2 inches (51 mm) above the finished threshold level. Liners shall be recessed and fastened to an
approved backing so as not to occupy the space required for wall covering, and shall not be nailed or perforated at any point
less than 1 inch (25 mm) above the finished threshold. Liners shall be pitched one-fourth unit vertical in 12 units horizontal (2-percent slope) and shall be sloped toward the fixture drains and be securely fastened to the waste outlet at the seepage entrance, making a water-tight joint between the liner and the
outlet. The completed liner shall be tested in accordance with Section 312.9. |
Dale Roberts CSI, CCPR, CTC, LEED Green Associate
Senior Member
Username: dale_roberts_csi
Post Number: 120
Registered: 10-2005
| | Posted on Tuesday, March 24, 2015 - 12:58 pm: | |
Tile and grout are not waterproof. They have varying degrees of water absorption. Add to this finishing errors leaving voids or cracks and movement and settling of the structure also causing voids and cracks, I would highly recommend waterproofing under the tile.
When I have done remodels where no water damage was expected (only remodeling to update finishes) I have seen water damage. So with the exceptions of the most economical jobs in any wet areas or Intermittent wet areas I would recommend an ANSI A118.10 waterproofing membrane under the tile.
In our Data sheet on Wonderboard we do state WonderBoard is not a waterproof barrier. If the area behind the backerboard must be kept dry, use RedGard waterproofing. |
|
4specs.com Home Page