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Message |
Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP
Senior Member
Username: specman
Post Number: 1053
Registered: 03-2003
| | Posted on Saturday, October 13, 2012 - 02:25 pm: |    |
The architect wants a masonry stain with an antigrafitti coating for exterior CMU. I've specified antigrafitti coatings before for unfinished brick and CMU; however, I've never specified a masonry stain before, which I assume to be is a pigmented water repellent.
Does anybody have any experience with a system that provides both?
Ron Geren, AIA, CSI, CCS, CCCA, SCIP
www.specsandcodes.com |
Guest (Unregistered Guest)
Unregistered guest
| | Posted on Saturday, October 13, 2012 - 04:18 pm: | |
You probably want to specify a water repellant over entire CMU surfaces, then anti-graffiti coating over lower reaches of walls (e.g., L.A. requires min. 9 ft.). I just specified such for brick masonry bldg. re-purpose project; although, no stain color, water-repellant product specified (Monopole) can be "tinted" (to semi-transparent appearance per mfr.) with latex paint...I just can't vouch for how it would actually look. |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 339
Registered: 12-2006
| | Posted on Tuesday, October 16, 2012 - 07:07 pm: | |
Ron, I've used silicate based masonry stains before on brick and CMU. Check out http://www.nawkaw.com/stains.html. There are others. Check with Glen Gery Brick for suppliers. Make sure to use the stain over the entire surface to ensure that the entire surface will weather uniformly over time. The silicate-based stain should remain vapor permeable and it should also help fill pores and harden the surface, making the wall easier to clean. Still, grafitti paints can be very hard to remove. Removal methods can leave ghost images that last longer than the grafitti.
As to anti-grafitti coatings, so many options and products have come and gone over the years I don't know who to trust or specify anymore. A few issues include:
1. Sacrificial Coatings: These are largely wax or fat based coatings that go on in several layers. When they are tagged, use a pressure washer to remove the grafitti and a layer or two, then re-apply. Usually work okay except they are non-vapor permeable and can look horrible every time it rains.
2. Sealed surfaces: This involves some form of a clear coating that seals the surface but that makes cleaning easy, supposedly without allowing the cleaning process to damage the substrate. Again, for it to be effective it will be non-vapor permeable. It also may not work, especially if the area is prone to frequent tagging (it may work once or twice).
3. Sinak Corp makes something called their HLQ 125. It's a hydrolyzed lithium quartz that hardens and densifies just about anything cementitious or masonry. The substrate will tend to retain some level of vapor permeability presuming it was when you started. I've never seen it change the appearance of any of the substrates I've used it on. I don't know that they advertise it as an anti-grafitti coating, but Bob and Craig Higgins are very knowledgeable and may have other options up their sleeves.
Whichever way you go, get several mockups. Tag them and clean them. Get them wet. See what they look like. Do not believe anyone trying to sell you a product. I'm convinced that many people selling these systems have never actually seen what they look like a year later.
One other factor to consider: CMU is by its nature very porous. Unless you select a very dense face (like a 'burnished block'), you're going to have difficulties protecting the surface from grafitti. |
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