The Handyman's Pocket Book: Fixings In Walls And Ceilings.

The chief factors here are the kind of wall in which the fixing is to be made, and the weight of the object being fixed.  In timber walls and partitions there is usually little difficulty.  Ordinary wood screws do the job perfectly well, unless the wood is thin, in which case bolts may have to be used - if it is possible to reach the other side.

WOOD PLUGS.  Brick walls require a different treatment, and plugging is necessary.  When there is no surface plaster wood plugs can be used, these being driven into cavities made in the mortar seams.  A strong form of plug is shown at A, Fig. 1.  It is about 0.75 in. thick and is thinned down to 0.375 in. at the end, the waste being taken off at an angle.  In this way the plug has a slight twist which give it a firm fixing.  A smaller plug, B, is made similarly, and is suitable when a fixing has to be made in the middle of a brick.  The carpenter generally cuts the taper with his axe.  Men not so used to the work will find a wide chisel easier to manage.  The recess to receive the plug is chopped with a cold chisel.

Both kinds of plugs are left projecting and are sawn off flush afterwards.  This can be hard on the saw, and it is a good plan to put a piece of card against the wall to prevent the teeth from being damaged.  One important point is that the end of the plug should not touch the bottom of the hole as this would prevent a tight fit.  Its tightness at the sides of the hole should prevent it from being driven in any farther.

Altogether, however, a more satisfactory fixing is made with one of the proprietary plugs such as Rawlplugs.  Their advantage is that they make much smaller holes, and give a stronger fixing for screws because in a wood plug the screw has to be driven into end grain.  For brick walls which have a plaster facing they are much neater.  Apart form the hole being smaller less knocking is necessary with less risk of plaster being cracked.  There are several forms of plugs, and for indoor work the fibre type is generally used.  An alternative for outdoor plugging is the lead type which is a sort of hollow lead cylinder with cup at one end to prevent it from entering too far.  The lead is better able to resist the weather.

When a fixing is needed in a crumbling mortar of plaster wall an irregular hole often results, and a plastic plug is sometimes preferred.  There is also a plastic compound which is pliable and can be squeezed into an irregular hole, and which will take up the shape of the hole, however crumbled and irregular it may be.

This is also useful for other types of walls because it saves having to stock several sizes of plugs.  Having made the hole (considerably deeper than the screw length), wet the plastic compound, roll into elongated form and press into the hole, forcing in with the special tool supplied for the purpose.  Make a hole in this with the pointed tool, again deeper that the screw length, and drive in the screw.

MAKING THE HOLE.  Large holes in the seams of brickwork are best cut with a narrow cold chisel of the type A, Fig. 2.  Smaller holes for the type of plug at B, Fig. 1, need the chisel at B, Fig. 2.  For Rawlplugs and similar types of proprietary plugs a special tool of the kind shown at C is preferable.  Various sizes of bits can be placed in the handle, and in use the tool is given a twist between the strokes of the hammer.

In indoor work there is always an element of risk that knocking with the hammer may cause plaster to crack, and when this is feared it is better to use a drill.  Special tungsten-tipped drills are available.  They are expensive, but they eliminate risk of cracking, and stand up to the work well.  A normal morse drill loses its edge quickly.

When it is desired to make a hole in the mortar seam of a brick wall it is sometimes difficult to locate the position when it is plaster faced.  One way is shown in Fig. 3.  The positions of the seams at the brickwork outside the window are noted and a mark level with one of them is made inside.  The height of this from the floor is measured so enabling corresponding marks to be made inside the room.

LATH AND PLASTER WALLS.  A lath and plaster wall requires different methods.  Heavy objects should be suspended only on the timber studding, though light items can sometimes be supported opposite the laths.  The problem is generally that of locating the timbers.  Tapping with the knuckles will often reveal a more solid feeling opposite a stud, and a fixing can generally be made anywhere vertically above or below.  When two have been located it is generally simple to find the rest since they are usually evenly spaced.

If there is a skirting in the room this will generally give a clue.  It is nailed in position and the nails naturally pass into the studding.  By examining the skirting and noting the nail positions it is only necessary to plumb a line above as shown in Fig. 4.  It is unlikely that a nail will be driven into every stud, but once two have been found it is generally easy to locate the rest.  As a rule they are not at greater distances apart than 13 in.

Sometimes a fixing is necessary in the space between the timbers.  The laths themselves are too thin to afford a reliable grip, and the most satisfactory way is to use a Rawlplug spring toggle as at (A) Fig. 5.  To use this the bolt is unscrewed from the wings, passed through the fitting to be fixed, and the wings rethreaded a few turns.  A hole is made in the wall big enough to take the wings when folded back, and the toggle passed through, the wings in the vertical position so that when they fly open they pass across two adjacent laths.  By pulling the fitting backwards the wings will remain in this position whilst the bolt is tightened.  Once driven right home the wings automatically remain in position (B).  It will be realized that if the fitting has to be removed at any time a new spring toggle will be required because, when the bolt is unscrewed, the wings necessarily fall down inside.

In the case of thin material such as insulation board, hardboard, plywood, etc. it is often more convenient to use gravity toggles (C) and (D).  In this case the single wing drops down by its own weight after being inserted in the hole.  It has a small spike projecting inwards so that it grips the back of the material when the bolt is tightened.  Sometimes it is more convenient to use Rawlanchors, especially when the material is soft or uneven at the back.  The Rawlanchor is passed through the hole (E), and when the bolt is tightened the flexible metal arms slay out as at (F).  Yet another fixing useful in some circumstances is the Rawlbolt which has a hard rubber portion which expands at the back when the bolt is tightened (G) and (H).

CEILING FIXING.  When a heavy object has to be fixed it is advisable to screw into the joists if practicable.  It this cannot be done a block will have to be fixed about the laths.  It is often possible to ascertain the joist positions by going into the room and noting where the nails occur which hold down the boards.  If the distance is measured from the wall (allowing for the skirting) is is an indication of where the joists are (see A, Fig, 6).  If, however, you have to go into a loft to find the joists, remember that there will be no plaster facing on the walls there.  It is also necessary in a tall building to see whether there is any diminution in the thickness of the walls.  This would, of course, throw out calculations.

If it is not possible to obtain a direct fixing to the joists a block can be laid on the laths as in Fig. 6, B.  This will support a light weight, but a better plan is that in Fig. 6, C, which the fixing block is screwed to the two side blocks, these in turn being screwed to the joists.  By this method the weight is taken by the joists, whereas at B the laths have to support the entire weight.  One other minor advantage is that the work can be done single handed, whereas at B it is necessary to have someone in the room above to press down on the block whilst the screws are being driven in.