We are working on a project where we are planning to use HAS-U M10 rods in conjunction with HY-270 resin to secure curtain walling into a sandstone substrate, with 100mm of embedment.
There is uncertainty on the allowable edge distance and spacing of the anchors into good-quality sandstone, as this substrate is not shown in your technical guidance or ETA-19/0160.
Furthermore, the loads on these anchors are very low (0.645 kN ultimate limit state shear force) so we feel that the current edge distance of 60mm and anchor spacing of 100mm shouldn’t pose a risk, but we need confirmation of this from yourselves.
Can you offer any guidance on what the allowable spacings should be in this instance?
Thank you for your enquiry, we don't have specific data for fixing into Sandstone. I can only suggest adopting an approach similar to the published data for HY270 (Which is most widely tested product for such materials) blockwork / masonry where the minimum spacing is 3 x the embedment depth so assuming the minimum embedment depth of 50mm you would be looking at 150mm spacing and for the edge distance, I wouldn't suggest not going below a minimum of 100mm. Of course, you are liberty, to conduct onsite testing in accordance with BS8539:2012 to establish allowable loads should you consider the above as being too conservative.
