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Expert tips on preparing old plaster walls for painting

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Owning a historic home has its own charm and unique advantages. These houses were constructed by genius craftsmen who paid attention to detail, and some have been passed over generations for hundreds of years. However, the walls may be degrading and may need a renovation or comprehensive paint job. Before working on the old plaster walls, there are a number of things you need to have in mind. Comprehensive preparation is very important because it'll ensure you don't work on any repairs in the near future. For the DIY enthusiastic, here are helpful tips before you can paint your walls.

Check for lead

Very old homes may use lead paint, so it's upon you to ensure that you're not working with lead paint, as it is dangerous to your health. Do yourself a favour and purchase testing kits from your nearest renovation store. Also remember to test for asbestos before you begin. If there's lead or asbestos paint on the walls, then any work done needs to be supervised by a qualified contractor.

Know the plaster you're working on

The kind of plaster used on the walls dictates the materials you'll use to restore it. If your walls are lime plastered, then using drywall or gypsum plaster materials to patch it up won't do you any good. Gypsum patches are not chemically compatible with lime plasters, so using them will pose a risk of premature failures. Lime plasters were used in the past due to their long lasting nature. However, they were replaced with gypsum plasters, which cure in a very short time frame. You can test the kind of plaster by dipping a small sample in muriatic acid; gypsum will form a white residue in it.

Replaster or patch?

The decision as to whether you need to patch the wall up or remove the plaster and apply a fresh coat depends on the degree of damage. If the wall seems intact with a few hairline cracks and minor damages, then filler is your answer. All you have to do is apply the filling material using a filling knife.

For more severe damages, you'll have to patch it up with plaster compounds. Apply the patch carefully and then leave it to dry before sanding it. You could then apply a bonding layer and finish it up with another layer of plaster. Doing so creates a smooth finish for large-sized damages.

However, if the holes are too large, and there's lots of loose plaster and cracks, then you may as well replaster the whole wall. This is also a good option if you want to get rid of the lime plaster that takes ages to dry. Simply remove the plaster and apply a fresh coat. You may get rid of more material than you should, making the process more complicated. Leave this to a professional plasterer.