Yesterday a 240° external corner PIR mounted on brick gave up the ghost after 10 years, as the IR-transparent cover had gone brittle and cracked, allowing water in. An identical replacement was no longer available, but Toolstation had something electrically similar (
I bought one and have just been looking at how it's mounted on the external corner. The bracket they supply for this is strong enough, but stupidly the holes for the supplied rawlplugs have to be drilled with their centres only 10mm from the edge of the corner! So, with the supplied plug, and a 6 mm hole required, there would only be 7mm of brick left. With two holes at 90° to each other, and only 15mm between them, the edge of the brick would be very weak. I also thought that using hammer action so close to an unsupported edge would be courting disaster. So I used a 4mm TCT bit without hammer action and slowly drilled the hole. That went ok, so I opened the hole out with a 5mm TCT bit. I found some 5mm rawlplugs which I could use with a thinner screw as well, as I reckoned the screw supplied would have put so much force on the expanding plug as I tightened it that the brick could easily split off. So far it seems to be ok, so tomorrow I'll complete the fitting.