Stucco Systems

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Author Message (Unregistered Guest) Unregistered guest Posted on Saturday, June 24, 2006 - 08:35 am:    We spec'd a conventional 3 coat cement plaster on wire mesh construction for outdoor ceilings in new museum project. The contractor is proposing a system such as Sto Powerwall. The project is in the Berkshires (the mountains of western MA). The construction is intended to be 1st rate - in other words, cost is not the primary issue. One last consideration: condensation. Since these ceilings are outdoors, we're concerned about hot days with cold nights and the possibility of staining caused by vapor in the cavity above the ceiling condensing & raining down through the ceiling. We will be venting the cavities, but still this is a concern. Thank you! Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 136 Registered: 10-2002 Posted on Saturday, June 24, 2006 - 06:35 pm:    “cavity above the ceiling” .....? Where is your thermal envelope? If it is in the same plane as the soffit, than there should be no issue with condensation except any condensation that might naturally occur on the soffit surface in the mornings. A good quality paint should be sufficient to protect the surface. If is above the soffit, ie, on the underside of the floor above or on a side wall, then you have an “attic” condition which should be fully vented as any attic would be ventilated. There should be no condensation conditions in a properly vented cavity. Exterior plaster, more commonly referred to as stucco, is a time honored system with a long track record. The old system can be improved on by the addition of additives in the plaster which can improve the moisture resistance of the surface. Contraction joints should be properly located. I can understand where a contractor would not want to use plaster. The availability of a qualified plaster (20-years experience of proven satisfactory performance in finishing plaster surfaces and who regularly smokes 3/4" thick cigars) would hard to get to travel outside urban areas (I am assuming the mountains in western MA would not be considered an urban area) not to mention the higher cost. Ron John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 545 Registered: 03-2002 Posted on Saturday, June 24, 2006 - 10:16 pm:    Sto Powerwall, according to their website, is tratitional stucco, but with polymer and fiber additives. It seems to me that if there is a moisture problem, you're better off with something like this rather than a non-modified stucco. However, the real issue is whether you have checked the moisture drive of the soffit assembly to see where your dew point is. Where are you placing the air barrier (required by code here in Massachusetts) and your insulation system? Many air barrier manufacturers will help you with this dew point calculation by doing a WUFI calculation. You might try contacting them for assistance. I don't think the issue of concern is the stucco, it's the assembly. (Unregistered Guest) Unregistered guest Posted on Sunday, June 25, 2006 - 08:18 am:    The stucco ceilings are uninsulated- one is at a porch and the other is at a loading dock overhang. Both are thin assemblies with flat roofs. The steel beams in these roofs( painted with Tnemec) are fairly tight to the top of the stucco assembly. We had a 1/2" open reveals ( with a baffle) at the perimeter for venting, but thinking about it, this is unlikely to be enough ( 23'x23' area divided into 4- there might also be venting at the 1/2" joints between panels). Thank you for your help. We will contact Sto for their recommendation as well. Richard L Matteo, AIA, CSI, CCS Senior Member Username: rlmat Post Number: 166 Registered: 10-2003 Posted on Sunday, June 25, 2006 - 02:47 pm:    If you haven't already, I would suggest you contact J. E. McLaughlin, Inc. They are the Sto Distributor for Western Mass. Covers Western MA, Main location in VT Contacts: Chaz McLaughlin Tel#: (802) 773-6258 Fax#: (802) 775-6450 800#: (800) 869-7514 Email: chaz@jemclaughlin.com Website: www.jemclaughlin.com I used them quite a bit when I worked in Connecticut. I found them to be very knowlegeable and very helpful. William C. Pegues, FCSI, CCS Senior Member Username: wpegues Post Number: 610 Registered: 10-2002 Posted on Sunday, June 25, 2006 - 08:24 pm:    And if you are in the need of multiple systems/manufactuers, Parex/Lahabra has an exact duplicate of Sto's Powerwall system. Sto in some areas is very difficult to get good technical information from. Some areas they are great. Nationally I have found Parex/Lahabra to be super everywhere even if the local was not so good because everything gets referenced back to the national office. Send me your email and I will send you some contact names. They are very up front about their products and will tell you where they may have differences or options that others don't have. My email is wpegues@wdgarch.com if you want to contact them. I know all the people I will refer you to personally, they have all been to my office. They are also typically at all the CSI Shows. William John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 546 Registered: 03-2002 Posted on Tuesday, June 27, 2006 - 08:48 am:    Being from Somerville, and enjoying Mass MOCA and Clark, I'd be curious as to what museum is under construction out that way. (Unregistered Guest) Unregistered guest Posted on Tuesday, June 27, 2006 - 08:52 pm:    Thank you all for your help. The Clark is building a new building on Stonehill in the woods next to the meadow. It will be complete in '07.