Weeps for stucco over CMU

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Author Message Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1115 Registered: 05-2003 Posted on Tuesday, July 08, 2014 - 09:14 pm:    We typically specify rope weeps as part of the CMU installation for new construction. A client has asked us to prepare a stucco spec for an existing CMU high rise façade with high moisture readings. I do not know if weeps were installed in the original CMU construction, the structural engineer's specifications do not reference weeps as part of the installation of the CMU in 2005. The original stucco has delaminated and is now being replaced, but the Architect wants us to specify a weeped stucco system, other than using weep screeds at story changes and the 'bottom" of the exterior wall, where else would weeps be deployed? spiper (Unregistered Guest) Unregistered guest Posted on Wednesday, July 09, 2014 - 09:29 am:    If there is already delaminated stucco then I am not sure that weeps alone are the answer. I would be more concerned about how the moisture is getting behind the stucco wall. Is it simply migrating thru the stucco or is there inferior flashing at floor lines, window heads, window sills, etc. Of course the extent of the problem depends on the amount of delamination and just how localized it is so maybe I am making a mountain out of a mole-hill. Lynn Javoroski FCSI CCS LEED® AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 1853 Registered: 07-2002 Posted on Wednesday, July 09, 2014 - 10:16 am:    Are they thinking of a drainage system? (EIFS?) Wayne Yancey Senior Member Username: wayne_yancey Post Number: 662 Registered: 01-2008 Posted on Wednesday, July 09, 2014 - 12:32 pm:    Jerome, Sounds like a job for a water managed system as Lynn noted. Please expand on the existing wall construction, particularly how the stucco is attached to the CMU. Other Questions: Is there a WRB, where is insulation and type, is there a vapor impermeable layer somewhere in the assembly? Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 668 Registered: 10-2007 Posted on Wednesday, July 09, 2014 - 12:32 pm:    If you are applying the stucco directly to the CMU how does the water flow down to the weeps? Reference to weeps as part of CMU installation could only make sense if the cells in the masonry units were not grouted. Typically in California all cells are grouted. In other parts of the country if all the cells were not grouted you will still likely see a good fraction of the cells grouted. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1116 Registered: 05-2003 Posted on Wednesday, July 09, 2014 - 01:46 pm:    There is no EIFS. This is stucco directly bonded to cmu/conc surfaces that have been prepped to receive the stucco, no wire lath, no WRB. Most of the time the prepping is the application of a bonding agent. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 669 Registered: 10-2007 Posted on Thursday, July 10, 2014 - 12:47 pm:    If the stucco is directly applied to the masonry units I do not see how weeps will solve the problem. Richard Howard, AIA CSI CCS LEED-AP Senior Member Username: rick_howard Post Number: 279 Registered: 07-2003 Posted on Thursday, July 10, 2014 - 01:24 pm:    The report at this link entitled "Stucco Failures and Remediation" was written specifically for Florida buildings with stucco directly applied over CMU. It looks at the shortcomings and offers some recommendations for mitigating the problems, including remediation. http://c.ymcdn.com/sites/www.nibs.org/resource/resmgr/BEST/BEST2_010_WB4-1.pdf ken hercenberg Senior Member Username: khercenberg Post Number: 800 Registered: 12-2006 Posted on Thursday, July 10, 2014 - 01:26 pm:    Is this a barrier wall design? Is the CMU single wythe or cavity/water managed? Keep in mind that the stucco and CMU are both porous so the assembly will wet and dry. As Anon pointed out in the other thread, with all of the insulation (what little there is) on the interior wall, moisture in the wall will condense when it hits the cold interior temperatures. This moisture has to go somewhere, probably towards the warmer surface (drying out). As we already discussed, trapping the moisture inside the wall with a vapor retarder is not a good idea. As Mark notes, directly applying the stucco to the CMU does not provide a drainage plane. If you are using a one-coat (acrylic-modified) stucco mix intended to block liquid water transmission, you may end up trapping water inside the wall, resulting in delamination of the stucco. If the CMU assembly is designed to drain (cavity wall), you're going to want clear drainage paths to the exterior; the more the merrier and open is better (cell vents, Mortar net, or MTI may be worth looking at). You don't want to cover these weeps with the stucco system. Extend the weeps through the face of the system. I have no idea what the existing configuration is. If you have any graphics of the existing construction I'd be happy to take a look at it and discuss it with you. I'm no building envelope 'expert' but I've screwed up enough projects to have learned some good ways to avoid problems. Let me know if you need my contact info. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1122 Registered: 05-2003 Posted on Thursday, July 10, 2014 - 04:23 pm:    Richard, Please be careful at using the recommendations in that report as is, the newly formed Florida Lath and Plaster Bureau's members having been looking seriously at that report and their comments have not been flattering. Now that you've introduced it on this board, I will try and share some of the recent comments and concerns, but the word asinine has come up frequently. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1123 Registered: 05-2003 Posted on Thursday, July 10, 2014 - 04:33 pm:    Mark, weeps won't solve the problem, the question of weeps was brought up by the Condo Association who is accusing the architect of not properly designing the stucco system. The association has brought in non-Florida based consultants who know little of how stucco is installed in Florida. In South Florida we are seeing Northern and infamous International architects specifying galv metal lath & WRB to receive stucco, that will last a few years before the lath corrodes from the moisture entering the façade as the stucco cracks. Non-corrosive lath would be much better, but that is seriously expensive and unnecessary over the entire wall if the stucco is applied correctly. Nathan Woods, CSI, CCCA, LEED AP Senior Member Username: nwoods Post Number: 586 Registered: 08-2005 Posted on Thursday, July 10, 2014 - 05:09 pm:    Wow, detail 8B is pretty scary in an open cell CMU wall. What holds the wall up once they cut through the block to kerf in the flashing? LOL. What is this detail trying to accomplish? Is it trying to force water into the wall? Detail 8A seems completely backwards too. Why would you want to the vertical reveal to run though? I thought the whole principle of water management detailing in stucco walls was to push the water out at regular intervals, reducing the static head of pressure in the water column created by a saturated wall of Portland Cement. I didn't read the body of the report, but those details are certainly suspect in my opinion. Helaine K. Robinson CSI CCS CCCA SCIP Senior Member Username: hollyrob Post Number: 398 Registered: 07-2003 Posted on Thursday, July 10, 2014 - 05:19 pm:    Who weeps for stucco over CMU? Sorry, couldn't resist. Jerome J. Lazar, RA, CCS, CSI, SCIP Senior Member Username: lazarcitec Post Number: 1124 Registered: 05-2003 Posted on Thursday, July 10, 2014 - 05:37 pm:    Nathan, no one in South Florida kerfs the CMU in new construction to receive flashing, its an insane detail. For existing construction, maybe, it depends on the condition.