Rainscreen WR Membrane

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Author Message John Hunter Senior Member Username: johnhunter Post Number: 35 Registered: 12-2005 Posted on Monday, July 30, 2007 - 06:38 pm:    I'm working on a rainscreen specification using Trespa panels and open joints. Henry's AirBloc 33 has been recommended for use as the weather-resistant membrane. We are concerned because it is not a self-sealing membrane and there will be many fasteners penetrating the surface. What have you all been using for the weather-resistant membrane in rainscreens? This project is in a fairly sunny portion of northern California, so UV resistance is an issue. Thanks. Wayne Yancey Senior Member Username: wyancey Post Number: 366 Registered: 05-2005 Posted on Monday, July 30, 2007 - 07:45 pm:    AirBloc 33 because it is UV tolerant and breathable. It is self-sealing. You best be talking to your local Henry rep. Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 220 Registered: 10-2002 Posted on Monday, July 30, 2007 - 08:47 pm:    AirBloc 33 is spray-applied and usually works well where there are numerous penetrations; ie, like in wall ties. What is the substrate? Can the panel supports be placed before the air barrier is applied? Harold S. Woolard, FCSI Senior Member Username: harold_woolard Post Number: 54 Registered: 12-2003 Posted on Monday, July 30, 2007 - 11:41 pm:    John, You can also use a product which is sprayed on and is breathable and self-sealing, and has a good UV rating, email praney@wrmeadows.com and he will let you know about Air-Shield LMP. He is from Northern CA area. Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 274 Registered: 01-2003 Posted on Tuesday, July 31, 2007 - 01:03 am:    Some membranes do seal well around nails, but screws are another matter. Ask the membrane manufacturer for tests for the fasteners you intend to use. Dave Metzger Senior Member Username: davemetzger Post Number: 212 Registered: 07-2001 Posted on Tuesday, July 31, 2007 - 01:24 am:    The membranes do self-seal around screws, but only if the screw is left in place. We use wording such as "When fastening anchors, if a screw misses a stud, do not back-out and re-drill screw, but leave the screw in place so as not to compromise the integrity of the air barrier." John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 767 Registered: 03-2002 Posted on Tuesday, July 31, 2007 - 08:43 am:    I was just discussing the self-sealing issue with my local WR Grace rep. He explained that the peel-and-sticks stay gooey througout their life, so seal by flowing onto the shank of the fastener. Screws are a little less forgiving than nails (as you would have in a shingle roofing underlayment), but they have done extensive tests and found that the membranes still self-seal with screws. The mechanism for the spray applied membranes is a bit different, because they cure into an elastomeric sheet. Here, the sealing is more like a gasket. While it is under compression, the membrane seals against the fastened item. Again, tests Grace has done have borne this out (so I've been told). John, we are also about to do a Trespa project, and I found the Henry product at the CSI convention. Here in Boston we've got a very broad range of weather conditions to deal with. We're on hold while permitting creeps along, so it sounds like you're a bit ahead of us. Wayne Yancey Senior Member Username: wyancey Post Number: 367 Registered: 05-2005 Posted on Tuesday, July 31, 2007 - 04:09 pm:    John H., Grace also has a comparible to Henry Airbloc 33. Named PERM-A-BARRIER VP. www.graceconstruction.com Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 608 Registered: 07-2002 Posted on Tuesday, July 31, 2007 - 04:28 pm:    John- we've used the Henry products in the NW for years -- I first heard of them from folks who had worked in Alaska. I've used both versions (permeable, and non-permeable) and have done very well with them. we seem to get equal usage from the spray applied and the sheet type, and I generally allow the contractor to choose which version they prefer to install. I use the same "don't back out the screws" language that Dave M. uses.