Archive through May 04, 2006

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Author Message Dale Hurttgam, NCARB, AIA Junior Member Username: dwhurttgam Post Number: 2 Registered: 10-2005 Posted on Wednesday, April 19, 2006 - 04:31 pm:    I wanted to seek your collective expertise and was surprised that I didn't find a thread for this topic. We are "old school" and still primarily specify urethane sealants. Locally, I believe the firms are mixed in this regard - work primarily in mid-west. With the advancements in silicone sealants, have most moved to using these extensively for exterior joints beyond just structural glazing? Interested in hearing your perspectives. Thank you. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 326 Registered: 07-2002 Posted on Wednesday, April 19, 2006 - 04:35 pm:    the silicones really can't be used for wide joints and so I stay with polyurethane for those joints only -- both horizontal and vertical. other than the wide-joint exception, I use silicone for everything; it has a longer warranty; it comes in multiple configurations, and it has good adhesion to most exterior products. Always do an adhesion test for each substrate and in some instances, silicone can "weep" into exterior stones, so do a sample for those products also. the contractors like the easier clean-up of the silicones, as well. George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 149 Registered: 11-2004 Posted on Wednesday, April 19, 2006 - 05:16 pm:    Dale I'm also in the midwest, and was like you old school. But I am being converted to silicones much more extenisvely. I think many of the staining or bleeding issues with silicones have been taken care of with some of the new products, but I do echo Anne's suggestion about adhesion testing and samples or mockups. One of the big advantages of urethanes to designers was the range of available and custom colors, but silicones are now available in a much wider variety of colors than when they were first introduced. [If color is important to you....taking off my designer hat and putting on my curmudgeonly specifier hat, "They all turn gray in a few years anyway."] Ronald L. Geren, RA, CSI, CCS, CCCA, MAI Senior Member Username: specman Post Number: 238 Registered: 03-2003 Posted on Wednesday, April 19, 2006 - 05:17 pm:    To add to Ann's comments, silicones at one time were very limited in colors (not any more) and had a problem with collecting dust (not any more). Not all silicones provide this, so you have to be selective. Richard Howard, AIA CSI CCS Senior Member Username: rick_howard Post Number: 74 Registered: 07-2003 Posted on Wednesday, April 19, 2006 - 05:35 pm:    I am located in the midwest, but have projects everywhere. We prefer silicone sealants for most exterior applications, especially in harsh environments and extreme conditions. Polyurethanes run second in preference generally and are favored in certain applications - for self-leveling sealant joints, for joints in precast parking structures (large movement), and for submersion service with urethane membranes. Dale Hurttgam, NCARB, AIA Member Username: dwhurttgam Post Number: 3 Registered: 10-2005 Posted on Wednesday, April 19, 2006 - 06:08 pm:    Thank you for the quick responses. Part of our concerns with silicone sealants were dirt collection and resulting staining, and joint prep/adhesion. I understand that improvements to silicone sealants have greatly reduced these concerns. I do understand that compatibility may still be a potential concern with silicones with respect to some materials such as the stone that Anne noted. I've also been advised that it is preferable to specify that the silicone sealants be SWRI(Sealant, Waterproofing & Restoration Institue)certified. As I understand it, the major advantage of the silicone sealants is the long term durability vs. small aditional cost, and the potential lack of owner attention to timely sealant joint maintenance Ron Beard CCS Senior Member Username: rm_beard_ccs Post Number: 127 Registered: 10-2002 Posted on Wednesday, April 19, 2006 - 06:21 pm:    George: < putting on my curmudgeonly specifier hat > That hat won’t happen to be triangular in shape is it? <g> Ron Stansen Specifications Member Username: stanspecs Post Number: 3 Registered: 11-2002 Posted on Wednesday, April 19, 2006 - 10:35 pm:    Am I wrong in my understanding that silicones are not paintable? If not, then color may be an issue in certain application since the range of offerings, while improved, still doesn't work everywhere. And if you can't paint it, then clear may need to be specified. Sheldon Wolfe Senior Member Username: sheldon_wolfe Post Number: 200 Registered: 01-2003 Posted on Wednesday, April 19, 2006 - 10:51 pm:    A less-than-ideal sealant color is a better long term solution than painting sealants in moving joints. Dave Metzger Senior Member Username: davemetzger Post Number: 159 Registered: 07-2001 Posted on Wednesday, April 19, 2006 - 11:14 pm:    I wouldn't paint any elastomeric sealant. Even though polyurethane sealants will take paint (silicones won't), the whole point of elastomeric sealants is to maintain flexibility to stretch and contract over the full applicable temperature range. This range of movement is more than (most) paints are designed to absorb, so a paint film will soon crack and spall from the sealant. Maybe an elastomeric paint could work (though I've never tried it, or even thought about it for that matter), but I don't know why you would want to try. I agree with Sheldon. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 327 Registered: 07-2002 Posted on Thursday, April 20, 2006 - 01:03 pm:    to continue: I'm located in Seattle and the cost issue for silicones stopped being "an issue" in this market at least a decade ago. Contractors cited the easier clean up compared to urethanes, so that while the material cost was higher for silicones, the labor was considerably reduced. Clear silicone will yellow. we find that in most conditions a black silicone joint looks better -- it is read as a shadow line, whereas the clear ones look sort of like a mistake. what we do in masonry and other exterior conditions is sand the joints: the joint is tooled and while still tacky, fine silica sand is pressed into the joint so that it mimics a grout joint. if you're next to the building you can tell the joint is there, but if you're ten feet away, you need a really good eye to make the distinction. You need to have this technique mocked up; in this area, most of the installers are familiar with it, but we don't always get good results in other parts of the country. Anonymous   Posted on Wednesday, April 19, 2006 - 05:24 pm:    I have never had any problems with using silicone for various joint widths. I have never heard of this being a problem. Could you please expand on this? Jonathan M.. Miller, FCSI, CCS, AIA eieio.. (Unregistered Guest) Unregistered guest Posted on Friday, April 21, 2006 - 03:19 pm:    I generally recommend specifying silicones, especially with their much longer warranty than urethanes, new formulations for non-staining & color selection. Ann is correct on advising using 'black' or relatively darker colored sealant joints to make them disappear visually. Another aspect to sealant invisibility is specifying a matte 'sand' finish vs. the smooth shininess that reflects. I usually picked this up during the mock-up stage but why not specify/recommend to the young architects going into the field? Anonymous   Posted on Friday, April 21, 2006 - 04:52 pm:    Anne - if you could please elaborate on your comments about silicone's inability to bridge large joint widths and your preference for urethane for these joints, I would appreciate it. What is too wide, in your opinion, for silicone, and how is using urethane for these joints any better? Your comment is inconsistent with my understanding of the performance characteristics of these two sealant types. John Guill AIA, CCS, SCIPa Senior Member Username: johng Post Number: 22 Registered: 07-2005 Posted on Tuesday, May 02, 2006 - 05:38 pm:    Suggest review product data for new silyl-terminated polyether, example product "Sonolastic 150"; very low-modulus, high-movement, nonsag, fast-curing, no solvent formulation, meets LEED and Calif air quality stds. Many advantages over conventional polyurethanes and silicon, including flexural, durability, paintable, unlimited color choice. Joint widths up to 2 inches (at Pac Bell Park in SF). More expensive than urethane, less expensive than silicones. Believe Sonneborn/Degussa may be only US mfr, importer. David R. Combs, CSI, CCS, CCCA Senior Member Username: davidcombs Post Number: 136 Registered: 08-2004 Posted on Tuesday, May 02, 2006 - 05:50 pm:    STS Coatings, Inc., GreatSeal PE-150 Polyether Sealant . . . is another. Phil Kabza Senior Member Username: phil_kabza Post Number: 167 Registered: 12-2002 Posted on Thursday, May 04, 2006 - 06:54 pm:    In the southeast, we avoid urethanes, due to their tendencies to revert in hot humid climates. You often see 5 year old urethane joints that are hard, cracked, and faded. We've had better long term success with silicones, subject to the cautions noted above.