This summer, we installed a new terrace of about 40m² (430 sq ft) with paving slabs and then, following the manufacturer’s instructions, applied the polymer jointing sand from the company Semin. The conditions were roughly 35°C (95°F), bright sunshine, and dry, light-colored slabs. We carefully swept the polymer jointing sand cleanly into the joints, thoroughly moistened it using a watering can, and allowed it to cure, before sweeping away any remaining residue. Then we experienced our blue miracle:
The jointing sand left an ugly gray haze on the previously bright and clean slabs. This haze was made up of tiny particles and turned all the formerly light-colored slabs a dull gray. But this was no big issue, no need to panic: the packaging stated that any leftover material would disappear over time.
Several days later—especially after some rain showers—the "new terrace" still looked embarrassingly bad. Friendly staff at the building supplies store where we had purchased the Semin product seemed familiar with this problem and connected us with the manufacturer. The manufacturer reassured us, referring to a "very special product" they would send us, which could easily remove the gray haze. However, this magic solution was not in stock and had to be ordered first. According to them, you just needed to spray it onto the slabs using a watering can, wait about 1–2 minutes, and then scrub the gray haze away "without any problems." When asked how the problem could have occurred in the first place, they blamed so-called "residual moisture" from morning dew or the like (??? at 35°C (95°F)???). So, we waited patiently for the "miracle cure" for our completely disfigured terrace (there are some striking photos available on request).
About four weeks and three puzzled calls to the manufacturer later, the long-awaited miracle arrived—three containers with French labels and appropriate warnings. To our great surprise, it turned out to be a simple cement residue remover (what a special product to have waited so long for!). We applied this, waited... and, as expected, nothing came off when scrubbing! A bit desperate, we tried to contact Semin again, but with little success. Through the friendly store employee we finally got a callback. They said they could not understand the situation, but would change the manufacturer’s instructions, and that we would receive compensation: the cost of the polymer jointing sand would be refunded along with all additional expenses.
Meanwhile, we had purchased six containers of cement residue remover and steel brushes at the store. After many hours of work on our knees, scrubbing the gray haze off the slabs, they finally looked as bright as when we started.
We are still waiting for compensation today (almost 4 months later). After many delayed and complicated phone calls (such as "we sent you a cheque—didn’t it arrive?" etc.), I think it is important to raise awareness of this general issue. I now also know that this is a fundamental problem with the product (see, for example, the beautiful pedestrian zone of Schweinfurt—the gray haze on all the slabs is remarkable!).
Of course, the manufacturer has not changed its processing instructions. We spent a lot of money on cement residue remover and steel brushes, and our knees hurt for days, our hands were raw from scrubbing. The manufacturer, Semin, is far away in France, so nothing really happens to them... Our conclusion: stay away from this polymer jointing sand, stay away from Semin—unless you have no high expectations for visual quality or enjoy delays and sore limbs...
The jointing sand left an ugly gray haze on the previously bright and clean slabs. This haze was made up of tiny particles and turned all the formerly light-colored slabs a dull gray. But this was no big issue, no need to panic: the packaging stated that any leftover material would disappear over time.
Several days later—especially after some rain showers—the "new terrace" still looked embarrassingly bad. Friendly staff at the building supplies store where we had purchased the Semin product seemed familiar with this problem and connected us with the manufacturer. The manufacturer reassured us, referring to a "very special product" they would send us, which could easily remove the gray haze. However, this magic solution was not in stock and had to be ordered first. According to them, you just needed to spray it onto the slabs using a watering can, wait about 1–2 minutes, and then scrub the gray haze away "without any problems." When asked how the problem could have occurred in the first place, they blamed so-called "residual moisture" from morning dew or the like (??? at 35°C (95°F)???). So, we waited patiently for the "miracle cure" for our completely disfigured terrace (there are some striking photos available on request).
About four weeks and three puzzled calls to the manufacturer later, the long-awaited miracle arrived—three containers with French labels and appropriate warnings. To our great surprise, it turned out to be a simple cement residue remover (what a special product to have waited so long for!). We applied this, waited... and, as expected, nothing came off when scrubbing! A bit desperate, we tried to contact Semin again, but with little success. Through the friendly store employee we finally got a callback. They said they could not understand the situation, but would change the manufacturer’s instructions, and that we would receive compensation: the cost of the polymer jointing sand would be refunded along with all additional expenses.
Meanwhile, we had purchased six containers of cement residue remover and steel brushes at the store. After many hours of work on our knees, scrubbing the gray haze off the slabs, they finally looked as bright as when we started.
We are still waiting for compensation today (almost 4 months later). After many delayed and complicated phone calls (such as "we sent you a cheque—didn’t it arrive?" etc.), I think it is important to raise awareness of this general issue. I now also know that this is a fundamental problem with the product (see, for example, the beautiful pedestrian zone of Schweinfurt—the gray haze on all the slabs is remarkable!).
Of course, the manufacturer has not changed its processing instructions. We spent a lot of money on cement residue remover and steel brushes, and our knees hurt for days, our hands were raw from scrubbing. The manufacturer, Semin, is far away in France, so nothing really happens to them... Our conclusion: stay away from this polymer jointing sand, stay away from Semin—unless you have no high expectations for visual quality or enjoy delays and sore limbs...
everl71 schrieb:
So here is our conclusion: stay away from this polymer joint sand, stay away from the company Semin – unless you have no high expectations for visual appeal or enjoy delays and sore extremities... Now I may correct myself: thanks to the intervention of an employee from this company, Mr. Weins, we have been reimbursed for all our expenses. Many thanks!
My advice for anyone looking to permanently keep weed out of their pathways, patios, etc., when using polymer-based joint sand:
Buy high-quality joint sand, make sure during installation that there is absolutely no residual moisture on the slabs or stones and that the temperature does not exceed 25 degrees Celsius (77°F). Instead of sweeping the sand into the joints with a broom, use a leaf blower to "blow" it in, then carefully moisten with a watering can, and everything should work fine...
Thanks to Mr. Weins, and following the above recommendations, I can now say: Semin is acceptable after all – maybe the manufacturer will even adjust their installation instructions "properly" one day, who knows?
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