Aerated concrete fall protection in window reveal

Hello everyone,

we are currently building a cabin out of aerated concrete (36.5 cm) and are facing the following problem.

We have floor-to-ceiling windows on the upper floor and would like to install a fall protection in the window recess. That means the windows are set a bit deeper inside and then three stainless steel rods are placed into the recess. We find this visually more appealing than installing fall protection on the outside.

Now my bricklayer told me that this won't work. The stone would chip off on the outside if I anchor rods in the recess. He suggests that I should chisel off a piece of the stone and fill it with concrete. That would hold better but would reduce the insulation value of the stone.

Now the question to you if anyone has already faced the same problem and/or has a solution proposal for it? Or are there possibly other fastening options?

I hope I have expressed myself clearly...

Many thanks Peter

For aerated concrete and this requirement, injection anchors could be the right choice.

Hello Peter,

Now my bricklayer told me that this does not work. The stone would chip off on the outside if I anchor rods into the reveal. He suggests that I chip off a piece of the stone and fill it with concrete. Then it would hold better, but reduce the insulation value of the stone.

I suppose it wasn't the bricklayer's best day...

Before he changes anything on the exterior facade and thus renders the thermal protection calculations invalid due to the concrete cushion, he should get in touch with Ytong or Xella (whichever stone was used). There he will receive reliable answers on how French balconies, which are fastened in the reveal, permanently withstand all forces – including horizontal ones. It would be new to me that a concrete cushion has to be installed in the reveal, and I have been working with aerated concrete for many years.

Best regards from the Rhineland

Thank you very much for the feedback.

My bricklayer only gave me the hint.
I will install the rods myself after the exterior plaster.

I will see if I can find a contact person at Ytong.
Thank you very much

Answer from the stone manufacturer::

Mounting within the window reveal is basically possible.

The manufacturer of the rods must provide you with the following information:
- Number of fastening points
- Type of anchors depending on the substrate (observe stone strength class)
Injection anchors with a BAZ must be used for this type of fastening.
The edge distances of the anchors used must be strictly observed for the position of the rods.

I have forwarded the questions to the manufacturer of the fall protection.
I especially hope for a statement on how high the edge distances of the anchors must be so that I can give the window installer the position of the window.

It remains exciting

The manufacturer of the balcony recommends a edge distance of 8cm based on experience. I will do a test drilling on a leftover stone and see if it holds or crumbles...