In the video below, I explain how to prepare cement foam board as a substrate for exterior (and interior) mosaics. I cover:
- How to cut cement foam board
- Button fixings and how to attach them
- Preparing the edges of your board for exterior use
In the video, here’s what I use:
- 6mm thick cement foam board
- Button-fix Type 3 (a triangular shape with two holes) (I also sometimes use Type 1 button fix – just make sure for both types that you fix them on the right way up according to the instructions)
- M5 T Nuts (5mm AN90 on Amazon)
- M5 countersunk bolts (16mm and also available on Amazon)
- Exterior adhesive (Mapei) mixed up with Mapei Latex Plus Admixture (50/50 water/admixture) and tinted with black Mortar Tone
Please check out some notes about Button-fix products below the video too…
I checked with the Technical Experts at Button-fix about their products for exterior mosaics. Here’s what they told me:
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Our general advice is that Button-fix fasteners are for interior applications. They are not designed to address differential expansion between panel and substrate or wind loadings that may act to lift the panel and disengage the Button-fix, which may often be encountered in exterior applications. We don’t want customers using our products on exterior cladding systems hanging 8’x4’ panels high on a building facade!
However, when used sensibly there is no reason why Button-fix should not be used in small-scale exterior applications, and we know several customers who have successfully used our fixings on exterior kitchen and bar furniture or for signage. Please ensure that the polymer button fixings (the green fixing for the wall) are not exposed to direct sunlight and that stainless steel screws are used. Polymer Button-fixes won’t corrode outdoors and, as long as they are not exposed to sunlight, will not degrade.
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So, as the Button-fix and polymer green fixings don’t get any direct sunlight when a mosaic is hanging, these fixings (both the Button-fix housing hardware and polymer button fixing) are good to use for smaller mosaic installations outside. I’ve used them successfully for over five years now.
If you’re taking down your mosaic for a while, remember to remove the polymer green fix too, so that it won’t be exposed to direct sunlight. (Button-fix also offers a special order option to create a stainless steel version of the polymer button fixings, for use if they will be left exposed for any length of time.)
Rhona Duffy 