ᐅ WeberMix 682 40m² Natural Stone Terrace – Negative Experiences

Hello everyone,
I’d like to share our terrace project from 2016/17 and, at the end, offer some conclusions about the different building materials and the manufacturers’ responses to justified complaints.

In summer 2016, we moved into our used house.
The outdoor area was in very poor condition.
So we didn’t hesitate long, and after a few drafts, it was clear that we wanted to build a completely new natural stone terrace with a roof and fence the entire garden to accommodate a robotic lawn mower.

Our local building materials supplier gave us mostly good advice when choosing the materials:

Subbase: 25 cm (10 inches) of 0-32 mm (0-1.3 inch) crushed stone (we used about 30 tons).
On top, a 12 m² (130 ft²) area of BiWood BPC (wood-plastic composite) full decking boards, laid on approx. 100 concrete slabs.
Surrounding that, 35 mm (1.4 inches) thick Nandi polygonal stone slabs, freshly laid into a 60 mm (2.4 inches) thick layer of trass drainage mortar.
For joint mortar, we were recommended WeberMix 682. More about this later.
Because neither a splash guard nor insulation was installed on the house’s ground slab, we took care of these during the construction phase in that area.
Around the terrace, we built a dry-stone natural stone wall on a gravel foundation 40 cm (16 inches) deep.
About half of it is covered by a terrace roof installed by a local specialist company.

Now we're enjoying a 40 m² (430 ft²) terrace, partially covered. Next, we plan to protect the weather-exposed sides with zip roller blinds and add an outdoor fireplace stove… but for now, after 1.5 years, a new open-plan kitchen with a panoramic fireplace is next on the list.

The demolition of the old terrace, including excavation for the crushed stone and stone wall, took about two weeks until everything that needed to go was removed.
Once around 10 tons of quartzite rubble were piled in our driveway, the real puzzle began. Building a dry stone wall requires a lot of patience. Meanwhile, the substructure was layered step-by-step. Two large block steps made from the same natural stone as the polygonal slabs complete the overall look. After a month, the new base was ready.

We installed a ring of LED ground lights around it and ran an underground cable into the base for power. The lights are also embedded about 1.5 m (5 feet) apart within the new splash guard.

We also buried the cable running down to the garden shed as part of enclosing the property border. I wired the shed completely in one weekend: sockets, lighting, decoration, outdoor lights, and the robotic mower.

Back to the terrace: next was determining the area for the BPC. We laid a ring of polygonal slabs around the footprint to find the ideal position.

Then about 100 concrete slabs had to be leveled and fixed in place as the base structure.

Quickly, we installed two foundations for the roof (50 mm (2 inches) PVC pipes, 80 cm (31 inches) deep, reinforced with four 2 m (6.5 feet) long rebar rods, then concreted).

The terrace roof specialists came and installed the roof over three days. Unfortunately, there were several complaints during this phase, but everything was eventually resolved.

We then installed the BiWood BPC decking, which was very convenient. Unfortunately, five boards arrived with defects. This was reported, and we received a goodwill credit.

Next, we spent about two days sorting and laying out the polygonal slabs. Given their size (approx. 60 cm (24 inches)), this was essential; otherwise, the result would not have been satisfactory. After positioning all slabs, we marked and photographed several corners.

Then row by row (starting around the BPC), we laid the slabs “fresh in fresh” using about 100 sacks of trass drainage mortar and 2 sacks of WeberXerm 854 flexible natural stone adhesive. From that point, the result looked impressively good.

Next came grouting. You might think that's the finishing touch, the cherry on top, so to speak.

We followed our supplier’s recommendation and applied 10 buckets of WeberMix 682. One bucket costs about €67.
This “mortar” isn’t a traditional mortar. It’s quartz sand that, when mixed with a resin from a separate can, forms a solid joint. The application is very simple: pour all ingredients into a bucket and mix thoroughly for at least five minutes until lump-free. Then simply spread the mixture evenly over the surface with a squeegee. The result looked very good, and after about 2–4 hours, the material begins to harden.

Visually, we were very pleased. We also properly installed raised beds, concreted edging stones, laid weed control fabric, applied 6 m³ (210 ft³) of bark mulch, and voilà…

After the terrace and garden were finished and heavily used that summer, we noticed we were constantly tracking sand into the house. At first, we didn’t think much of it and simply washed and swept the terrace.

But it didn’t improve. We started paying closer attention to the sand formation and swept everything up. It filled a full shovel!

Concerned, we performed abrasion tests in several places. We found that the material could be rubbed off with the sole of a shoe. We contacted the building materials supplier and initiated a complaint. After much back-and-forth about appointments (some clearly don’t realize you sometimes have to do work yourself), a field representative from Weber finally came.

He listened first and rubbed on the mortar. Then he started “finding hollow spots,” claiming there was water trapped under these areas and therefore it hadn’t cured properly… what an absurd explanation.
I politely but firmly explained that:
- The abrasion appears on the surface,
- There is a 60 mm (2.4 inch) thick layer of drainage mortar beneath the slabs, so water cannot accumulate under the mortar,
- The abrasion occurs evenly across solid and the supposedly “hollow” areas alike.
I also asked how a sand-resin mix could hollow out under the surface during squeegee application, which he couldn’t answer.

He also had no solution or plausible explanation. I offered to take a sample. Since a roof post was damaged by the roof installers during follow-up work, the joint there was already broken.

The Weber representative chiseled out multiple samples down to the drainage mortar (the entire depth of the joint) and then left, saying they would get back to us… which they eventually did. See the last photo.

I received an email from the building supplier with Weber’s response. At that moment, I nearly lost it:

“Visual inspection showed that the joint material can be rubbed off by finger. A weaker surface layer can thus be confirmed.”
So far, so good...

“The laboratory test showed no deviation from normal quality.”
Excuse me? This means the sample met the expected standard? So a weak surface layer is “normal”...

“Possible causes of sanding out:
- Rain fell on the surface within the first 8–10 hours after application, partially washing out the binder layer.”

WTF? Rain under a 20 m² (215 ft²) roof?? And during a rain-free week?
Not to mention the binder is not just partially washed out but crumbles down to the drainage mortar.

…The best part is yet to come…
“- Water was added during mixing of the joint mortar.”
Sure thing—I'm just an idiot who ruins my terrace finish by randomly pouring water into a two-component product because I can’t follow a simple instruction. Makes perfect sense. That’s why the entire terrace is messed up—because of my “clumsy hands.”

They still had one more:
“- The filler was not sufficiently mixed with the binder.”
Logical… just dump bucket, add can, stir twice, and then shove lumpy stuff on a €25,000 terrace… can’t see it later anyway…

I’m getting mad again…

“For the above reasons, we cannot accept this complaint.”
Ridiculous.

The final recommendation:
“Subsequent consolidation of the joint surface is not advisable…the joint mortar should be completely removed and the terrace surface re-grouted.”

Dear heads of Technical Support North and Central,
I couldn’t have put it better myself. You should scrape your rubbish off my terrace and use a competitor’s product instead. I’m available anytime to arrange appointments.

So, dear forum members, I strongly urge you: avoid the so-called WeberMix 682 joint mortar. It looks easy to apply but is the worst waste of money. If you don’t want to live on a sandbox and care about your terrace project even half as much as we do, go either with a competitor or use classic joint mortar.

When it comes to complaints, the company doesn’t shy away from dragging out the most ridiculous and flimsy excuses from their lowest drawer… but they’ve come to the wrong place with us. After repeatedly pushing the guy by phone over their statement, the competent man will “graciously” come back soon for a second sample. In the end, if we don’t see results soon, we’ll either have someone come redo it or bring the company to court with an independent expert opinion.
And of course, we’re happy to share honestly with you their level of competence and methods—free of charge.

We will keep you updated.

Hi, it’s frustrating what you’re dealing with here, but issues like this are quite common with polygonal slabs. I can recommend products from tubag quickmix here, as they don’t sand even if the mortar is applied a bit more fluidly. A light rain during drying will also cause some warping.
Don’t let it get you down,