ᐅ Calcium silicate block with cavity: Which fasteners are suitable for a balcony solar power system?

Hello.

These blocks are supposed to have been used in my building. When drilled from the inside or outside, there is a cavity after about 4 cm (including plaster) deep. The drill dust is white, so it is probably calcium silicate brick. Unfortunately, I did not measure the depth of the cavity. I also asked our local building materials supplier what these blocks might have looked like back then, but they had no knowledge about that. And whether the blocks shown on the internet represent the original structure?

It would be great if someone could help me with this.

The reason for my question is that I want to install a balcony solar power system on the wall. With such a large cavity, this might be difficult.

I am also unsure about the mounting options for the solar power system. I have been in contact with many sellers regarding the wall mounting. They send drawings that do not provide any clear information. After further inquiries, they go quiet. Does anyone have more details about the mounting points on the wall?

Your core drill sample shows that "sand-lime brick" is indeed the correct assumption for the material, given the initial guess of "sand-lime brick or clay brick." A wall thickness of 30 cm (12 inches) was common for the construction period, while 28 cm (11 inches) monolithic walls did not exist then or now. Clay bricks from before the Reich format would only have been used in "reconstruction in rubble" after 1955, and their drill dust would never have been white.

So, you will be dealing with sand-lime hollow block bricks. These are called that for a very literal reason: after about 4 cm (1.5 inches) of the outer web, the first hollow chambers appear, which is completely normal. For your project, you can find suitable anchors at specialized suppliers as standard industrial products and even as stock items; you will not need to have custom ones made. The cavities in the hollow blocks are not a defect or a material fault—they are what give the material its name. Everything is fine. This structure makes them easy to work with for masons and, as proven technology, they are still state of the art, though no longer produced in the 300 caliber.

However, this exterior wall construction has a poor U-value (thermal transmittance). Your main challenge for fastening will therefore be the insulation material that will be added in an energy-efficient retrofit.

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Felix571 schrieb:

It would be great if someone could help me out.

You can check with the usual suspects, for example with

nordanney schrieb:

You can check with the usual suspects. For example, at

The issue with the anchors has already been resolved. There are special anchors designed specifically for this purpose. My problem is the attachment. It has to hold in strong winds and storms. From the looks of it, the fasteners each have only two fixing points (perhaps two more holes could be drilled into the rails, which would then provide four fixing points). If the cavities aren’t too deep and the special anchors reach into other walls, that would change things significantly. That’s why I’m asking about the composition of the blocks. It can’t necessarily be assumed that these blocks are still produced in this exact form today.

In fact, the wheel was not reinvented with the stones. My advice, therefore, was to choose the anchors according to the load, and if possible, use ones that are two sizes stronger or longer.

It would definitely help if you could show your planned fastening system.

Felix571 schrieb:

That’s why I’m asking about the masonry structure. It can’t necessarily be assumed that these blocks are still available today in this exact form.

Sand-lime bricks are still available today. Blocks with a size around 300mm (12 inches) are probably no longer common on the market, but their structure is similar to the still common ones around 240mm (9.5 inches); they are not as finely cellular or finely ribbed as cellular clay blocks. You can embed the dowels in mortar.

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