Holes in plasterboard and lathe and plaster
Holes will need to be pre-filled in some way before plastering to blend in with the surroundings.
Filling small holes in plasterboard
You may, with small holes, be able to get away with using newspaper soaked in a thin mix of filler to pack the hole to a little below the surface. Then simply fill as normal when dry.
Or, cut a piece of plasterboard large enough to cover the hole, but small enough to be fed through the hole on its diagonal. Make a hole through the board and secure a string to it with the aid of an old nail. Paste its edges with filler and pass it through the hole – keep hold of the string. Pull it back to stick against the inside of the hole. Allow to dry before cutting the string and filling in the normal way.
Filling large holes in plasterboard
For bigger holes, the patch will need more support. If there are wood lathes showing, a plasterboard patch can be fixed with filler to these.
If there is no support showing, increase the hole sideways to find the wooden studwork both sides of the hole, then cut a piece of plasterboard a little larger than the hole. Position this over the hole and mark its outline in pencil. Now, using a craft knife and straight edge, cut out the hole to the same shape. Once done, the plasterboard will fit perfectly and can be fixed in place with plasterboard nails or dry lining screws. The latter will give superior grip and cause less vibration.
Mix some topcoat plaster and spread over the repair using a steel trowel. If the recess is deeper than a couple of millimetres, apply it in layers. The final layer should be allowed to dry until it becomes solid to the touch. Using a clean dampened trowel, the surface can be smoothed using a sweeping action.