One of the project architects came up to me this morning to talk about a project that is currently under construction. This project has a brick exterior skin and apparently when the joint sealant contractor applied the exterior joint sealant around the exterior openings (louvers, storefront, etc.), he went back and applied some kind of sand to the sealant before tooling it. According to the PA, the contractor told him that it doesn’t affect curing, helps with tooling and the PA loves it because it looks like the adjacent mortar joints. Has anyone else used this process before? Any pros or cons (because the PA would love to use this process in the future)?
Yes, I have seen it before. On a historical preservation pre-bid walk-through, an experienced mason told me about this practice. (He probably used “mason’s sand” - at least that’s the term my friendly mason used.) There is a manufacturer of sealant that makes a “pre-sanded” sealant, too. I’m not sure which manufacturer, but it’s a common one and you can probably find it.
sanding sealant joints is the ZGF standard and it is used on every project. you have to use smooth silica sand, it has to be done when the joint is tooled and still tacky and it has to be “thrown” or hand patted in. you can’t pat it in too much or it looks like a sealant joint. the point is that its supposed to look like a mortar joint.
it doesn’t void anything, but I would suggest getting about 5 mockups because if they aren’t used to doing it, they won’t do a very good job at first.
and no, the textured sealants don’t look the same.
in fact… I have the sealant manual from UniPro Sealants in Seattle and their spec for sanding the joint is:
“use nothing larger than 45-55 mm aggregate. sand should be equal in size to prevent settlement. it should be water washed, dust free and kiln dry.
there are many ways to install the sand after tooling the joint:
“cup a handful of sand in your hand and rub it across the joint”
“use a 4” dusting brush, piling a mound of sand on the brush and rub it across the tooled joint”
“simply grab a handful of sand and throw it on the sealant like throwing a baseball. make it look uniform in appearance”
if you mix sands, be sure to mix them often because they will settle in the bucket."
It was just called to my attention that 45-55 mm sand is about 2 inches wide. I’m guessing that’s the screen size used to sort it, but I will send a correction to UniPro for their next manual…