We have the task of fixing a bathroom cabinet weighing 16lbs to a tiled, plasterboard bathroom wall. The cabinet is supported at the four corners using metal slotted holes inset into the back of the cabinet. The screw heads pass into the holes and then the cabinet is lowered a short way so
That the slot locates behind the screw head.

The plasterboard would be standard 12mm and the thickness of the tiles with adhesive would be about 9mm. So, any plug would need to accommodate a wall thickness of about 21mm and the screw head would need to be quite small to fit the slotted hole. The threaded part of the screw would also
Need to be held firmly by the anchorage to take the weight of the cabinet.

The only two suggestions I’ve had to date are using butterfly toggle fixings directly or use these fixings to fix board to the wall and then screw cabinet to board.

Can’t fix battening to joists as joists are not in correct position for cabinet.

Any advice you have would be appreciated

You can use plastic wall anchors. If the cabinet is already in place, drill through the back of the cabinet the size needed for the wall anchor, then you will need washers larger than the hole to use w/ the screws so the screws will work properly.

Since the joist are not in the correct place to fit the attachments on the back of the cabinet then I suggest the following. Locate where two of the joist are and place the cabinet where you want it and then drill through through the cabinet back and into the wall where the joist are located. Use enough screws to make the cabinet secure and make the screws long enough to make sure the cabinet will hang there with the weight of the stuff you are going to put into the cabinet.

Hello Skiberger - I take it you're suggesting ignoring the proper means of hanging this cabinet (screw heads in slots at rear of cabinet) in favour of just screwing through the back panel of the cabinet. Not sure how strong this is and of course it is not flush to the back of the cabinet - it's inset from the rear edges of the cabinets sides. Screwing from the inside against this will deform it.

Also I have been advised by people in the trade that plastic anchors will not work where a wall is tiled. They can't bite into the side of the tile!

Hello letmetellu - (I've just cottoned on to your name "let me tell you"; thought it was aboriginal at first!) You've totally confounded me. The vertical joists are offset from where we want to put the cabinet and also will not be the same width as the cabinet (they're probably wider)! If you put battens across the two vertical joists, the cabinet will still be in the wrong position horizontally.

Sorry to appear negative, but don't really understand how either suggestion will work.