Sealants

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Author Message Dewayne Dean Senior Member Username: ddean Post Number: 90 Registered: 02-2016 Posted on Friday, September 16, 2016 - 11:29 am:    Our office master has this listing: "Silicone Sealant: ASTM C920, Grade NS, Class 25 minimum; Uses NT, A, G, M, O; single component, neutral curing, non-sagging, non-staining, fungus resistant, non-bleeding." Can one type of sealant cover all of these requirements? Thanks for all who contribute to these forums. Such a great resource Wayne Yancey Senior Member Username: wayne_yancey Post Number: 790 Registered: 01-2008 Posted on Friday, September 16, 2016 - 11:42 am:    Yes B. Silicone – General Purpose (Designation S-GP): ASTM C920, Type S, Grade NS. 1. Class: Joint movement range without cohesive/adhesive failure: Plus 50 percent to minus 50 percent of joint width. 2. Uses: NT, M, G, A, and O. 3. Low to medium modulus, single component, neutral curing, nonstaining, nonbleeding. 4. Acceptable Products: Dow Corning Corporation; 790, or 795. GE Silicones; SilPruf LM SCS2700. Pecora Corporation; 890 or 895. Sika; Sikasil WS-290 and WS-295. Tremco; Spectrum 1 or 3. Brett Scarfino (Unregistered Guest) Unregistered guest Posted on Friday, September 16, 2016 - 02:31 pm:    Dewayne - one sealant, perhaps, however priming becomes necessary for different substrates, based on project specific preconstruction test results with your substrates. Avoiding primers is a positive thing in my opinion, and perhaps a reason for so many different sealants. Wayne has listed a collection of high quality silicones I've seen and used numerous times for general applications, however for non-bleed/low stain potential applications (note - preconstruction testing required for manufacturer to standby their "no-stain" claim): Dow Corning 756 SMS ("surface modified sealant") GE/Momentive Silpruf NB ("non-bleeding") General purpose silicones only capable of +/-25% movement....this is low performing (on par with a polyturethane) and would require doubling the width of a caulk joint to handle the same amount of movement relative to a +/-50% sealant. For a 1/2" of movement, do you want a 1" or 2" sealant joint? Dewayne Dean Senior Member Username: ddean Post Number: 91 Registered: 02-2016 Posted on Friday, September 16, 2016 - 03:39 pm:    Thank you gentlemen