ᐅ Grinding/milling terrace concrete? 2–4 cm thick, no slope

Hello,

I have an unpleasant task ahead of me and would like to hear your opinions on the best options and solutions.

Our terrace was concreted, but the slope is not correct at the front and back. Tiles will also be installed. I cannot add more material because that would make the terrace door too high.

The terrace is about 38m2 (410 sq ft), and I need to lower it by about 2-4cm (0.8-1.6 inches). Of course, not the entire area, but most of it needs to be adjusted.

Is grinding alone sufficient here? Does it need to be milled first and then ground? I plan to rent the necessary equipment. Is it realistically possible to grind down 2-4cm (0.8-1.6 inches) of concrete?

It’s very frustrating, but you always learn afterwards...

Thanks in advance!

No, that is probably too much. We once had a situation at work where the floor of an underground garage entrance was poured too high. The company ended up chipping out the concrete over an area of about 12 square meters (130 square feet) because that was more cost-effective and faster. Milling is usually possible for depths of about 1-2 cm (0.4-0.8 inches), but it is also extremely expensive and time-consuming. Apparently, there are no machines that can work efficiently at this scale, like those used in road construction.

Myrna_Loy schrieb:

No, that’s probably too much. We once had an issue at work where the floor of an underground garage entrance was cast too high. The company removed the concrete over about 12 square meters (130 square feet) completely by breaking it out, as this was more economical and faster. Milling is usually possible only in the range of 1–2 centimeters (0.4–0.8 inches), but it is also extremely expensive and time-consuming. Apparently, there are no machines that can work efficiently on that scale, like those used in road construction.

So breaking out means piece by piece, right (Hilti)? And then grinding? If milling, I would just do several passes, but then the floor has to be ground again, right? Unfortunately, that is a dirty job. Dust and dirt everywhere...

Tiles on terraces, especially on areas exposed to moisture, are always quite problematic. They will freeze sooner or later—usually sooner.

Sanding the surface is not really an option. The only practical solution is to remove everything and try again. That means using an excavator with a breaker hammer to completely remove the concrete. Then reinstall formwork with a slope and pour new concrete.

Alternatively, you can leave it as is, install tiles, and build a terrace roof over it. That should work even without a slope.

In the picture, it’s also unclear how much clearance there is up to the door. I would say a slope of about 3 cm (1.2 inches) over the terrace depth is completely sufficient.

I don’t want to take over the thread, but what about around 0.5cm (0.2 inches)? Which device could be used for that? For me, it’s more about the garage and only an area of about 2-3 square meters (21-32 square feet).

ullw889 schrieb:

I don’t want to take over the thread, but what about around 0.5cm (0.2 inches)? What kind of tool could you use for that? In my case, it’s more about the garage and only an area of maybe 2-3 sqm (22-32 sq ft).

The screed installer had a grinder, similar to the one used for parquet flooring. He smoothed the garage floor with it and removed the laitance layer. I’m not sure how much concrete was actually ground off, but it looked like it could work.