The advantages of GftK joint mortars

What pointing products do you use? We’re betting that it’s sand and cement. You understand their foibles and are pretty reluctant to experiment with anything else, especially when you're throwing a customer into the mix (not literally!) and want to ensure a good job. Are we right?

vdw 850 used for Grouting Granite Sett Driveway

Finished project using GftK vdw 850. Built by PDG Groundworks.

Bear with us, though, because at London Stone we've found an alternative that, after giving it a tough workout ourselves in comparison with the alternatives, we're very happy to recommend.

You don't need us to tell you that traditional sand and cement mortar needs to be applied in optimum conditions and kept dry while it cures. Even if you've got the most precise mix, any residual water between the slabs, or any poured on by the heavens, will alter the ratio of moisture to cement and is likely to result in increased shrinkage and reduced strength. So, in the cold and damp, especially at this time of year with the ever-present prospect of rain, you don't really have much choice but to wait for better conditions before you can get on with the job.

Here's the alternative. It'll seem more expensive than traditional mortar at first, but when you take into account ease and speed of application (saving you considerable time), the fact that you can apply it in almost all weathers (so you're not held up on a job), and the fact that you won't be called back to make repairs, it suddenly looks a whole lot more economical than the alternative.

1. Add the hardener to the pail ref D328-031 reduced

Adding hardener to the epoxy resin-coated sand.

GftK Paving Joint Mortars consist of epoxy resin-coated sand mixed with a hardener that creates a free-flowing mortar that is applied as a slurry with lots of water (in fact, you really can't use too much water). In practice, this means 3-4 minutes to mix the tub to the right consistency, then 20 minutes to brush in the contents of the tub. With two to three men working, you'll finish two to three hundred square metres in a day, even in the pouring rain.

2.1 Mix until homogeneous ref D328-029 reduced

Mixing the sand and hardener until thoroughly combined.

It's also an enormous saving on your body. We've found that, once people have used these mortars, they really don't want to use anything else. Why? Well, a huge bonus is that they can be applied standing up, with a long brush. No more time on your knees, compacting the sand and mortar.

3. Pour Out and apply the vdw 850plus by squeegee with lots of water reduced

Applying GftK Joint Mortar

GftK hardens to a permeable, high-tensile mortar that prevents weeds from growing, resists the burrowing activities of ants, bees and other annoying insects, and doesn't fall prey to freeze-thaw action. It won't stain stone, so even if some is accidentally left on the surface of sensitive stones like limestone or Indian sandstone, it doesn't cause a problem.

4. Rinse off the Residual vdw 850plus with plenty of water reduced

Rinsing off residual joint mortar with plenty of water

The vdw 815 and vdw 850 that we supply are very similar. Both are highly suitable for domestic and commercial patios and for light to medium vehicular traffic on driveways. They're abrasion-resistant, even when it comes to mechanical sweepers, and unaffected by de-icing salts. They'll also withstand high-pressure water-jetting with no problem (check out similar products and you'll often find that a power-wash requires certain precautions). The difference between 850 and 815 is in the grading of the sand, making vdw 815 suitable for joints up to 3mm wide, and vdw 850 for larger joints (try using the 850 in 3mm joints and it just won't fit in).

5. Brush off any final Residual vdw 850plus from the paving units (2) reduced

Brushing off any final residual joint mortar

Are there any times when we wouldn't recommend using GftK? Only when the temperature is really low, below 3ºC. This is because, if there's a chance of frost, the formation of ice crystals will interfere with the mortar's self-compacting action, weakening the structure. However, low temperatures in general are no hindrance as, although it slows curing, the mortar will continue to cure when the temperature increases again above 8-10ºC.

Mechanical Street Cleaning - No problem with vdw 850 Jointing Mortar - med rs(1) reduced

Here vdw 850 stands up to simultaneous high-pressure water-jetting and mechanical abrasion to no ill effect.

So that, in a (rather large) nutshell, is why we recommend GftK. We've tried it ourselves and are confident you'll really like it. A bonus is that free training is offered on site. So, not only will you gain confidence, knowing that you're using the products correctly, but you'll get a job completed  and won't lose any working time. Pretty good, huh?

If you'd like to apply for a free on-site training session, just get in touch with us at

By London Stone Blog | Published 22nd January 2016
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