How to Repair Plaster Walls
You may find it necessary to repair plastered walls at times when redecorating does not follow, especially after attaching fitments of various kinds to walls, or removing them. The damaged plaster should be prepared by scraping any loose plaster from the cavity, at the same time raking the edges of the cavity with the point of a trowel or putty knife, to undercut them. This is done to provide a ‘key’ for the new plaster inserted in the hole. After removing the loose plaster the inside of the cavity and the surrounding area should be thoroughly wetted with water, applied with a brush. This is done to remove dust from the cavity, also to prevent the too-rapid hardening of the new material by absorption.
There are many different kinds of patent powderwhich may be used for repairing- damaged plastered walls and the handyman will find these much easier to use than plaster of Paris, which hardens very rapidly and will be found difficult to handle. The method of mixing patent powder is general to all different makes. A small basin should be partly filled with water, the powder from the carton should then be sprinkled on the water into which it will sink. When the powder commences to float on the surface, this indicates that the proportion of powder to water is correct; the surplus water should be poured away, and the should then be beaten into a smooth paste with a putty knife.
The filler may be applied to the repair with a putty knife or small trowel and if much repair work is to be done at one time it will be advisable to use a ‘hawk’. This device is used to transfer the filler from the mixing bowl to the place of work. The hawk simply consists of a piece of square board, fitted with a short length of broom handle, secured with a single.
If the repair area is a small one, the filler can be inserted in one go, but before it is applied to the repair the cavity and the surrounding area should again be thoroughly wetted with water. Press the filling well into the cavity so that it is forced into the undercut sides and smooth it level with the surrounding surface, using the edge of the cavity to guide the knife.
The repair should be left overnight for the filler to harden and then lightly gone over with a piece of worn grade middle-two glass-paper. The choice of tool used for applying the filler may be varied according to the requirements of the worker. Some handymen use a trowel for this type of repair, others prefer the use of a broad stripping knife of the type used for removing old wallpaper. The filler used for repairing has a very fine texture which will leave a perfectly smooth finish.
In the case of large areas of repair, the cavity may first be partly filled with a coarser and cheaper material – ‘Sirapite’ is suitable for this purpose. This is mixed and applied in exactly the same way as the finishing filler, but the surface of the foundation filler should be cut with the point of a knife to make deep criss-cross marks. The surface filler is then applied in the usual way and this may be done immediately after using the foundation filler.