rainscreens

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Author Message Brian E. Trimble, CDT Senior Member Username: brian_e_trimble_cdt Post Number: 112 Registered: 08-2005 Posted on Wednesday, February 06, 2019 - 05:32 pm:    Does it bother anyone that rainscreens are buried in 07 42 00? Rainscreens are becoming a larger part of wall cladding and it seems like they deserve a more prominent heading. I might recommend a totally new Division, maybe Division 15 Cladding, but that may cause some people's minds to explode. I think most of Division 07 has elements that are hidden (insulation, flashing, air barriers, etc.). Anything that is exposed (roofing, siding, etc.) doesn't have to appear in Division 07. At least give wall panels a Level 2 number and get rid of any roof panels from that section. Does anyone else have concerns with specifying rainscreens or am I just spitting in the wind? Jeffrey Wilson CSI CCS SCIP Senior Member Username: wilsonconsulting Post Number: 270 Registered: 03-2006 Posted on Wednesday, February 06, 2019 - 08:41 pm:    I wouldn't say rainscreens are "buried" in 074200. For rainscreen systems made w/ "wall panels" the location makes sense -- and the majority of them have traditionally been wall panel systems. Brick cladding designed as a rainscreen is typically addressed in Div 04. I have spec'd highly customized decorative metal rainscreen assemblies in Div 05. GFRC rainscreens would be spec'd in Div 03. So any rainscreen can be spec'd in the section appropriate to its "work results." I don't see the need to segregate them in a particular location or create a new Division. Jeffrey Wilson CCS CSI SCIP Wilson Consulting Inc Ardmore PA James Sandoz, AIA, CSI, CCS, CCCA Senior Member Username: jsandoz Post Number: 252 Registered: 06-2005 Posted on Thursday, February 07, 2019 - 08:51 am:    It would seem, as a work result, rainscreens properly belong in Division 07. For example, by another logic (describing a predominant material instead of the work result) ACM panel assemblies could be in Division 05. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 890 Registered: 01-2008 Posted on Thursday, February 07, 2019 - 09:16 am:    Brian, Rainscreens are a tactic or strategy or a construction assembly for water management. Offering drainage, drying, deflection employed by drained/back-ventilated (most common) or pressure equalized (less common) rainscreen systems. They are not a section #-title. Both systems employ open joinery and allow a certain amount of water into the cavity area between the outer and inner leafs. Drained/Back-ventilated systems rely on the ventilation cavity to both drain and dry-out the residual water. Pressure-equalized systems (PERS) employ drainable compart-mentalization to limit water penetration during periods of pressure disequilibrium and to facilitate rapid pressure equalization. PERS greatly minimizes and under certain weather conditions can eliminate water in the rainscreen cavity. Since these wall systems are constructed from several inter-related components (from diverse MF Divisions and sections) which must work together to obtain the stated performance standards, there is much confusion in the design and construction community about how these inter-related components should be specified, contracted and con-structed. There isn't one section for rainscreens. ken hercenberg Senior Member Username: khercenberg Post Number: 1215 Registered: 12-2006 Posted on Thursday, February 07, 2019 - 10:14 am:    Hi Brian. I would advocate that you submit a proposal to the MF committee to find an appropriate location for a holistic rain screen Section. I consider the correct location to be a subset of Section 018316 "Exterior Enclosure Performance Requirements" since, as noted above, there are so many possible variables. This Section would permit the Specifier to present a holistic system with appropriate cross references to the applicable component parts spread across any number of Divisions such as Div 04 for masonry veneers, Div 05 for CFMF, Div 06 for sheathing, Div 07 for air, water, thermal, and possibly vapor barriers and possible skin systems, etc. It can be used as a single repository for communicating performance requirements and can coherently direct the Contractor to other Sections that address mockups, testing, and other activities that affect the building envelope. What do you think? anon (Unregistered Guest) Unregistered guest Posted on Thursday, February 07, 2019 - 01:25 pm:    I am not finding any instance of "rainscreen" or "rain screen" buried anywhere in MasterFormat. Where are you finding this, Brian? One problem with introducing the term "rainscreen" into MasterFormat is that there is no universal definition. One person's "rainscreen" is another person's brick veneer, or drained and ventilated system, or open jointed system, or pressure equalized system... etc. Perhaps, if you are to propose this change as suggested by Ken, you might also propose a definition. My suggestion would be: Rainscreen: An exterior wall assembly consisting of a primary line of defense (cladding) against bulk water intrusion and a secondary line of defense (water-resistive barrier) designed to direct incidental moisture out and away from the wall assembly.