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Hi everyone.
We've recently had some large standstone blocks installed and I'm looking to add some aluminium batten fencing ontop.
My question is about attaching the posts to the blocks, the normalish way I'm pretty sure is to core drill and grout the posts in.
How ever im wondering if anyone has ever used anka screws in sandstone before? Or is it just too soft for the threads to bite in and hold?
Anka screws are rubbish for attaching any materials that will be subjected to any kind of buffeting from wind, gates opening/closing etc. even if they're in brick or concrete. I would expect that you are correct that sandstone, being a softer material, would not hold an Anka screw for even very light duty purposes. Dynabolts would do an equally poor job as you would risk cracking the stone. A system using chemical fixing methods would be the way to go.
Core drill it or if you prefer a fixing bolt system use epoxy injection and a stud which you can get in a standard silicone gun cartridge. By far the easiest way to go
The simple answer is to do a test with both. You might be surprised how good the gripping power of an anka screw is. For a dyna bolt if its not to close to an unsupported edge then that should be ok to.
Chemset.
Not knowing the density of the particular sandstone you are using it could vary from very soft (almost chalky) very coarse sand like, to very dens (like iron stone) very fine high density stone and also if it has clearly defined grain patterns or mono coloured with virtually no grain pattern and also how big are these blocks and proximity to an edge will the anchors be.