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I am planning to install a Northcoate Metro letterbox, like this one https://northcotepottery.com/products/metro-letterbox. Referring to this YouTube presentation https://www.youtube.com/watch?v=oPAZOzp0ar4, how would others out there rate the holding or, for want of a better word, staying potential of these units if they were attached (using Liquid Nails or the like) to a concrete slab? The letterbox base only allows for adhesives to be applied around a relatively slender skirt around the perimeter, bring into question the staying power of the letterbox-slab connection, especially if the letterbox is subjected to a heavy strike, say, from a postal motorbike or from vandals.
Welcome to the Bunnings Workshop community @few8609. It's sensational to have you join us, and many thanks for your question about installing a letterbox.
The holding power of the adhesive around the skirt would be more than adequate to keep the mailbox in position through normal use. If you are talking about large impacts, the lightweight fibrecement would likely crack before the adhesive lets go. However, if you'd like to create a more positive connection, I'd suggest Dynabolting a timber frame to the concrete slab that matches the dimensions of the hollow internal base of the letterbox. That way, the skirt would be glued down, and a far larger portion of the internal walls would be adhered to the timber frame. Provided you then slap the letterbox and say out loud "That ain't going nowhere." the installation will be bullet-proof.
Please let me know if you have any questions.
Mitchell
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