joint sealant types

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Author Message Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 959 Registered: 01-2003 Posted on Wednesday, March 15, 2017 - 11:35 am:    I've received a number of inconsistent recommendations from joint sealant reps. *Polyurea should be used for control joints in concrete slabs. *Polyurethane sealants are better than silicone for concrete slabs. *The people who install acoustic sealants prefer polyurethane, even though acrylic sealants work for those applications. Over the years I've moved to specifying polyurethanes for interior non-moving joints and joints in concrete slabs, silicone for all other moving joints and all exterior joints, and acrylics for acoustic sealant. What are you doing, and why? ken hercenberg Senior Member Username: khercenberg Post Number: 1061 Registered: 12-2006 Posted on Wednesday, March 15, 2017 - 11:53 am:    There are some good polyurea sealants for use with concrete. I use them more for higher traffic areas especially vehicular traffic. Polyurethane is fine for typical office building type applications. Polyurea sealants are obviously more compatible with polyurea coatings such as at vehicular bridge conditions where a more robust system is called for. My defaults match yours almost exactly. While still hesitant, I do use Use T silicones at horizontal joints with limited traffic though I'm told that they've worked out the kinks. Essentially I don't like transitioning between silicone and urethanes; I don't believe the transition holds up over time if at all. I rarely use urethanes at exterior anymore unless I am directed to by the client and I always document dissent. As to acoustics, I go with whatever was tested in the assembly if there is one. Otherwise I usually specify acrylic. I understand urethane may be easier to work with and will certainly hold up better until it's painted. When the paint dries and shrinks, I've had sealant joints split. Firestopping is, of course, its own discussion. Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 960 Registered: 01-2003 Posted on Wednesday, March 15, 2017 - 12:10 pm:    Thanks, Ken. One thing I forgot: silyl-terminated polyether and silyl-terminated polyurethane sealants. One rep said they're midway between polyurethanes and silicones in cost and longevity. I've known about them for several years, but no one is pushing them and I haven't received any prior approval requests or substitution requests, so I wonder who's using them. ken hercenberg Senior Member Username: khercenberg Post Number: 1062 Registered: 12-2006 Posted on Wednesday, March 15, 2017 - 12:22 pm:    I only use STPE for air barriers. As far as I know they are compatible with both urethanes and silicones but I haven't checked that in real world testing. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 805 Registered: 01-2008 Posted on Wednesday, March 15, 2017 - 12:50 pm:    STPE (Silyl-Terminated Polyether) is the chemistry for the air barrier sealant (R-GUARD AIR DAM over closed-cell backer rod) used by PROSOCO as an integral part of their interior air/water barrier system. STPE sealants (i.e. BASF Sonneborn; Sonolastic 150 with VLM Technology) are also used for exterior sealing with wood and fiber-cement sidings. They are paintable. Other fluid-applied air/water barrier sources such as Dow also use the STPE chemistry. Brian Payne, AIA Senior Member Username: brian_payne Post Number: 78 Registered: 01-2014 Posted on Wednesday, March 15, 2017 - 02:32 pm:    I was just having a conversation about how I hate writing the sealant section mainly because of the huge amount of type/application combos. Also, I have always seen the Joint Sealant section as a catch-all for sealants that don't fit nicely anywhere else in the spec, like between two separate systems. I appreciate the recomendations. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 807 Registered: 01-2008 Posted on Wednesday, March 15, 2017 - 02:34 pm:    Brian, Please contact me at wayne.yancey@crtkl.com. ken hercenberg Senior Member Username: khercenberg Post Number: 1063 Registered: 12-2006 Posted on Wednesday, March 15, 2017 - 02:54 pm:    Wayne, I think the Dow system is silicone like the GE/Momentive. I've used the GE/Momentive system with extruded silicone strips for trim and flashing. Really good system but probably a little more expensive than some of the others. Still, it should last longer too.