Joined: July 2004
||Posted: 24 April 2019,10:08
|Quote (DNgroundworks @ 13 April 2019,13:55)|
|GFTK mortars are permeable which makes me wonder of they are susceptible to frost damage. The product data sheet does require a permeable bedding layer but who lays flags like that?|
Must have missed this last week - hope I'm not too late....
Frost? The 2-part resin mortars laugh at what we call frost in this counbtry. They are widely used in Germany, Scandinavia, Russia and lots of *really* cold places, not just countries that get a bit niuppy for a few days in January. They are practically immune to frost damage.
The permeable bed recommendation is because the mortars are intrinsically permeable, and so they perform best when laid over a free-draining substrate. When used with a typical British sand/cement bed, they tend to act as moisture reservoirs, which leads to them turning green with algae pretty quickly.
I wrote about this here
Power washing or use of a good quality biocide tends to control the greening, but use of a permeable bed really does make a HUGE difference, and becaiuse that method oif installatuion is pretty common in Europe, we see the recommendation on the data sheets for all sorts of jointing mortars made over there.
And as for asking who uses permeable bedding, the answer is we all will be using it, and sooner and you think, as it is more-or-less certain to be a requirement of the revised British Standard and will increasingly become a part of the "manufacturers' installation advice" that we are obliged to follow to ensure it's not our arse that gets kicked if paving goes wrong.
There are proprietary permeable bedding mortars, such as the truly excellent SteinTec TuffBau TuffBed, but a basic equivalent can be made by mixing around 300kg cement per cubic metre of clean 6mm grit to create a sort of Rice Krispie textured mortar/concrete.
I will be writing a LOT more about these bedding mortars in the years ahead. Like Garlic Bread, they *are* the future! In Germany and much of northern Europe, it's known as Trass bedding and that is likely to become the term we end up using, mostly due to their being no suitable, snappy English term that describes the mortar quite as well - why re-invent the wheel?
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