Chemical anchor or expansion anchor?

[RichardRR]

I have a cast balcony from 1964, about 10cm thick with a lot of stone/aggregate. It's not brand new and shows some signs of cracking. I am now going to attach concrete angles/L-brackets on the underside, which will in turn serve as mounts for railing posts.

The expansion anchors I have found for cracked concrete have a recommended drilling depth of around 90-95mm minimum, which is a bit too deep since I have a new waterproofing layer that's just over 100mm.

I would like to drill a maximum of about 70mm deep and am considering using anchor adhesive and threaded rods instead. I'm thinking of drilling 12mm holes and using 10mm stainless threaded rods. Is there anything specific to consider when choosing expansion anchors or anchor adhesive? The tricky part is that the holes are drilled on the underside of the balcony, and I want to ensure that the anchor adhesive doesn't "run out" of the holes before it has cured.

Best regards,
Richard

 

[Snickarkirre]

I would probably go with anchor adhesive in your case if you don't want to drill deeper than 70mm. Remember to clean the holes properly with a "pipe cleaner" to remove all drill debris. There are special brushes for that. Most of the dust will come out by itself but it's good to ensure nothing is left in the holes. I don't think anchor adhesive will run out as it is quite viscous and hardens quickly.