Simple steps to repair cracks and holes in internal walls

There are lots of products available at your nearest DIY shop, but you will certainly need a general purpose filler for small cracks and holes, and a tougher DIY repair and skimming plaster for larger jobs. Have a fine surface filler to finish and smooth for a professional appearance. Be patient with this kind of DIY task; admit that you will take longer to finish the job than a professional tradesman would. 

First, clear away furniture and put down a dust sheet. For small hairline cracks first ease the fracture open with a Stanley knife to make it bigger - not too much! This is just to ensure that the filler can get into the gap and grip itself in there. Brush out any loose material or dust, and spray with water ready for filling. 

Fill the gap using the plastic spreader that came with the filler, or use a specific filling knife. Push the filler into the crack or hole, spreading to even off the edges with a 'feathering' motion to give a flush professional finish. 

Larger holes and cracks need more care and attention. To begin with, remove all dust after cutting back the edges of the damaged area all the way back to the sound plaster. Spray again with water, and add the filler in layers of around 5mm or 1/4 inch thick. Lightly score the filler in a criss-cross pattern so the next layer can grip onto it. Press in well and engage your patience while you leave it to dry completely. Add more layers as needed to fill the hole or crack, and spread to even off the edges on the last layer, feathering at the end for a smooth finish. 

If you have an area of damage over 1m², you will need a professional plasterers trowel. To start with, chip off all loose edges and clean away the dust. Press in your repair plaster with the trowel and use smooth upward strokes to fill the gaps. Press down firmly and evenly to reduce the need for heavy sanding at the end of the job. Once the holes and gaps are filled, move to a fine surface filler to get rid of any air holes, finishing off with the feathering technique to smooth off the edges. 

If the cracks or holes appear in the corners, you can fix this using a straight batten, a long flat strip of squared timber. Lightly nail the batten level with one edge of the corner, leaving the other side of the crack or hole exposed. Fill as according to the severity of the damage, smoothing the surface level with the batten. Once the filler is completely dry, remove the batten and repeat for the other side. 

For perfect smooth finishes on all your filling jobs, lightly sand the areas with a fine sandpaper when the filler is completely dry, and apply an undercoat before painting with your internal paint, or add a lining paper before hanging your fancy wallpaper.