Waterproofing of split face CMU

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Author Message Margaret G. Chewning FCSI CCS Senior Member Username: presbspec Post Number: 190 Registered: 01-2003 Posted on Tuesday, August 31, 2010 - 05:51 pm:    Have an interesting problem for you, need to know what you would recommend. my client (D/B project) is asking about providing waterproofing/waterrepellant on the exterior walls of our project. The exterior wall is single wythe split face CMU, with insulated and grouted cells; half the building has the interior face of the CMU wall furred out with metal studs, batt insulation and Gypsum board; the other half of the building, the inside face of the CMU exterior wall is exposed. Both areas are occupied space. the project is in Colorado. From previous masonry seminars, I learned that to provide a water repellant on an exterior masonry face was looking for spalling due to possible trapped moisture behind the sealant. Especially in northern climes where freeze thaw issues abound. Is there a product that would be suitable or is it still not recommended? George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 557 Registered: 11-2004 Posted on Tuesday, August 31, 2010 - 06:11 pm:    Silicone coatings, from 20 or 30 years ago, didn't work because they trapped in vapor, as you suggest. Silane siloxane blends were the product of choice a few years ago. They would keep out liquid moisture from the outside, but let any moisture vapor from the inside pass out. ProSoCo, Euclid, and similar all have products. I don't remember which of the parts of the blend, silane or siloxane, is a smaller molecule, but it is possible to tweak the blend depending on specific conditions. Silicone is a surface coating, silanes and siloxanes are penetrants. Euclids literature has a great diagram explaining the difference. If I can find a copy, I'll send it to you - or it may be on their website. George A. Everding AIA CSI CCS CCCA Cannon Design - St. Louis, MO Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 878 Registered: 03-2003 Posted on Tuesday, August 31, 2010 - 06:26 pm:    We use a lot of single-wythe masonry in southern Arizona. I use silane almost exclusively, but siloxane is also acceptable. Silane has a smaller molecule, so it can be used on denser concrete to get maximum penetration. Siloxane, with a larger molecule, will work on the porous concrete products like CMU. You might investigate the use of integral water repellent in the block and mortar, but coordinate its use with the penetrating sealer, since the integral repellent may minimize penetration of the silane or siloxane. Refer to NCMA TEK 19-2A for design of single-wythe CMU walls. Ron Geren, AIA, CSI, CCS, CCCA, SCIP www.specsandcodes.com Lisa Goodwin Robbins, RA, CCS, LEED ap Senior Member Username: lgoodrob Post Number: 86 Registered: 08-2004 Posted on Wednesday, September 01, 2010 - 09:59 am:    Single-wythe masonry exterior walls (without the addition of insulation as you mention above) have not been allowed in Massachusetts since the 2001 energy code was enacted. We sometimes specify integral water repellent for block and mortar equal to the following: 1. Grace Construction Products; Dry-Block and Dry-Block Mortar Admixture. 2. BASF Construction Chemicals; Rheopel and Rheopel Mortar Admixture. If this is D/B, then it probably won't matter; however, many design Architects are surprised that the addition of these products changes the color of the block wall. Steve Gantner, CSI, CCS, CCCA Senior Member Username: sgantner Post Number: 25 Registered: 08-2007 Posted on Wednesday, September 01, 2010 - 10:16 am:    This is an interesting subject. In St. Louis, it is rare that we are asked to use a single wythe masonry wall, but when we are, there are a number of options. First, I would suggest you use a product similar to Blok-Flash in the first course to get any water out of the wall that may get in through cracks or un-observed defects in construction. Second, given our location and proximity to higher seismic design categories, we are grouting about every 24 inches on center and installing reinforcing. It may be less expensive for you to create a barrier wall by grouting all cells solid. This may also help with the insulation value of the wall by creating a "mass wall" as defined by the energy code, depending on which one you are using. Third, because it is single wythe, we insist on a blend of silane/siloxane, similar to Tenemec's Prime-a-Pell. Once this product is applied, you can not tell it has been treated until it rains. I have also been told that they can last up to 10 years or so, but will need to be reapplied at some point in the buildings life. The smaller molecules penetrate deeper into the block to prevent moisture intrusion, while the larger molecules keep the direct water on the surface. This is where the problem of small cracks rears it's ugly head. The silane/siloxane blends are not elastomeric and will not bridge cracks. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1236 Registered: 03-2002 Posted on Wednesday, September 01, 2010 - 04:36 pm:    Though silanes will not bridge cracks, there is some resistance to water penetration. The treatments make the block hydrophobic, which combined with the surface tension of water, help keep water out of cracks. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 1000 Registered: 07-2002 Posted on Thursday, September 02, 2010 - 02:54 pm:    the ONLY product I have ever used that would waterproof single wythe CMU is a masonry coating from Tnemec. I don't know of any "clear" coating that can do the job, and would strongly advise the owner against doing such a thing, especially in a freeze/thaw climate. This is absolutely a bad idea and doomed to failure. However, if you must: first, use the ""dry block"" additive in the CMU and also in the mortar and grout. This helps quite a bit, actually. Then go with a block filler, and high build coating on the masonry. Have it applied by licensed and experienced applicators. the rough surface of the CMU is going to really cause problems with this, because it just multiplies the amount of surface area. Now, I realize that the high build coating pretty much obscures any design intent that you might have, but really --- I would advise your partner in charge that this is a guaranteed leak situation and have the client provide a hold harmless. (and in response, in the northwest, we fully grout all block walls and provide reinforcing every 18 or 24 inches on center in both directions. While it may protect the interior a little bit, it generally means that the building takes longer to get saturated and then stays that way longer. this is a really dumb idea except for an exterior storage room, garage or trash enclosure. In fact, the only time I do single wythe masonry anymore is for trash enclosures. J. Peter Jordan Senior Member Username: jpjordan Post Number: 451 Registered: 05-2004 Posted on Friday, September 03, 2010 - 10:30 am:    I worked on a project in Hawaii a long time ago where 6-inch CMU was used for the exterior walls. On the windward side, many of the walls leaked. We initially thought it might be joint failure, but I now know that CMU is, in and of itself, not a very good weatherproof material. The leaking water was simply an inherent quality of the material itself. I now usually refer to CMU as a cementitious sponge. Split-face and split rib products are even worse. I recommend to my clients that they only use these in veneer applcation where "rain-screen" (masonry veneer construction) principles can be appled. Some of the big box stores will use split-faced CMU and then paint it or coat it with an elastomeric coating which preserves texture, but kills other aesthetic qualities. While penetrating water repellant products will help and elastomeric coatings may be even more effective, it is my view that CMU should not be used in a single-wythe wall as the weather barrier, period. (Unregistered Guest) Unregistered guest Posted on Friday, September 03, 2010 - 07:15 pm:    Margaret, First off, please refer to ASTM standard D1079 for the definition for waterproofing; it is not the same as water repellent. Integral water repellent, such as Grace's Dry Block, works incredibly well when installed correctly. Correct installation, for single wythe CMU, requires double buttering of the head joints and a mortar water repellent admixture (provide by Grace when the CMU has the water repellent specified). It is a good idea to involve the local Grace rep, if possible, to make site visits occasionally and make sure that the block is being installed correctly, and that the water repellent is being added to the mortar in the proper way and in the correct dosage. A penetrating water repellent can be applied in addition to the integral water repellent, but not strictly necessary. Don't let Ms. Whitacre scare you off from this. Here is a link to one of my favorite examples of single wythe exterior decorative CMU building (with Grace Dry Block) that has been performing flawlessly for many years: http://en.wikipedia.org/wiki/Kirkland_Performance_Center There are many more examples that you can get from your local Grace rep, I am sure. ken hercenberg Senior Member Username: khercenberg Post Number: 60 Registered: 12-2006 Posted on Saturday, September 04, 2010 - 03:35 pm:    The fatty products like DryBlock are a start, not an end and can be messy in hot climates where the fats can literally extrude out of the CMU pores during high-lift grouting. I agree that if you want to go clear you should be looking at high solids silanes. Protectosil by Evonik Degussa (or whoever owns it this week) has a product called Chemtrete BSM400 that I've had good success with. Here is a link: http://www.protectosil.com/product/protectosil/us/products/water-repellents/Pages/default.aspx. Margaret G. Chewning FCSI CCS Senior Member Username: presbspec Post Number: 191 Registered: 01-2003 Posted on Saturday, September 04, 2010 - 04:16 pm:    Thanks to all of you for your advice. The client and end user has elected to go for a clear sealant system IE the high solids Silanes on the face. As this is not in a hot climate I'll also look into an admix for the CMU and mortar.