Before making fixings into solid masonry, make a couple of test drillings to find out whether the wall is built of brick or lightweight blocks. It brick is identified from red or yellow bore dust, use ordinary plastic wall plugs; but if grey dust suggests lightweight blocks it is better to use a proprietary block plug which has larger ‘wings’ to grip the softer material. In either case the screw must be long enough to penetrate at least 38 mm long into the masonry behind plaster, so use screws are at least 62 mm/21/2 in. long for a plastered wall. Increase this 1.0 75 mm/3 in for fixings that will carry heavy loads. Screw gauge 8 will be adequate for normal loads; increase this to gauge10 for 75 mm/3 in screws. Make sure, too, that the screw and wall plug sizes are compatible, and take care to drill the holes are right angles to the wall surface, deep enough to accept the screw length.
Making fixings to stud (dry) walls poses fixing problems. Cavity fixing devices such as spring or gravity toggles and cavity anchors can be used only for fixings that will carry the lightest loads. For any other use, the fixing must be made either to a horizontal twigging (cross bridging)fixed between adjacent scuds difficult to fir except during construction of the wall framework — or directly to the vertical studs themselves. These will have to be located with an electronic stud finder or, less satisfactorily, by wrapping and test drilling — they are usually at 400 mm/16 in or 600 min/24 in centres. Make sure that pilot holes are drilled into the centre of the stud, not near its edge, since this could result in a weak fixing. Use screws 50 mm/2 in long for medium loads, 75 mm/3 in long for heavy ones.
MAKING FIXINGS IN MASONRY
1. Mark where the fixing is to go and use a masonry drill, sized to match the wall slip. Wind tape around the drill bit to act as a depth guide.
2. If the drill has an adjustable depth stop attachment, use it instead of the tape to set the drilling depth. Drill until the stop touches the wall surface.
MAKING FIXINGS IN PLASTERBOARD (GYPSUM BOARD)
1. If the fixing must be between joists or studs rather than into them, drill a clearance hole for tile fixing device through the plasterboard
2. Push a cavity anchor into the hole so it can expand against the hack of the board, and drive in the screw. Using toggles, thread the screw through the object first.
3. Choose a wall plug sized to match the screw being used, and push it into the hole, insert its rim is flush with the wall. Tip it with a hammer if necessary.
4. Thread the screw through a clearance hole drilled in the object being fixed, insert it in the mouth of the wall plug and drive it home.
5. Alternatively, use long-sleeved frame plugs. Drill holes through the wood and into the wall, insert the plug and tighten the screw to make the fixing.
MAKING FIXINGS INTO STUDS
1. Use an electronic stud finder to locate the stud or ceiling joist positions. It works by detecting the nails which secure the plasterboard (gypsum board).
2. When the stud or joist positions are marked, drill clearance holes in the object to be fixed at matching centres. Check these for accuracy.
3. Drill pilot holes through the board surface and into the stud or joist. Make sure that the drill bit is at right angles to the surface of the wall.
4. Insert screws into the clearance holes, then offer up the object to be fixed, align ii with the pre-drilled pilot holes and drive the screws home.