Can someone tell me what size screws and plugs to use to fasten electric back boxes to wall as not sure which are best preferably from screwfix thanks
Inch & quarter number 8 screws and red plugs 5.5 mm masonry bit is my preference, depends on type of wall
Cowboy, I use inch and a half. All depends on what the walls like though, I've had to use 4 inch screws/mortar/nail guns/frame fixings, you name it and I've attached a box to the wall with it before now.
The correct screws to use are round head black Japan screws, although it is a lot of years since I have seen this done. You do come across it on some older installations though. https://www.tcfixings.co.uk/main/ma...k-Japanned-Round-Head-Woodscrews/189/0/0/1/12
Blimey that is old school!!, back in the day light switch boxes were often secured with a masonry nail through the middle hole.
Just how old are you? That is a borderline era for carbon dating, almost as far back as a whittled wooden spike or hatchet wedges.
Of course it's not right unless you use one of those hammer driven rawlplug chisel drill things and brown fibre rawlplugs or that asbestos paste stuff you squidged into the hole!
Remember the first year joiners/carpenters cutting the wedges with an axe, after cutting out the holes with a plugging chisel, for the grounds for the plasterers to plaster to and for the chippies to fixing the skirtings to.
Cowboy job, with round heads the idea is you cannot catch/cut the cable with the sharp edge of an ordinary countersink screw.
I was taught that myself in college fifteen years ago, they’d also hammer them into openings and fit door linings and window boards to them, although I thought it was pointless at the time as I’ve got older and hopefully a touch wiser I do think that it’s important to teach the old ways to try to shape a learner into an all rounder, rather than just stick to the last twenty years of gripfill and foam, though I do like both of those products.
Not for the door linings and window and door frames, but I felt for the young apprentices having to do house upon house of grounds.
Rewires and newbuilds always used them, could not see the point not using them. All you needed was the Electrical Clerk of Works to pull up on it, for a silly thing like the wrong screws and you would have to change them all. Not worth the hassle.
Why would a round head screw stop the cable getting damaged if it got trapped against it, the insulation of the cable is still the softest thing inside the box and it will split no matter what it gets trapped against, and you also have the two sharp edges on the round head screw where the slot is anyway. Another load of nonsense dreamed up by a jobsworth again.