"How to fix drywall" may be a popular search question because it seems like the repair is super simple. For a professional drywaller or plasterer, yes, it's very simple. But one of the things customers tend to forget about is the mess involved with any simple repair, especially plaster or drywall repair.
Drywall does not normally crack across the board itself, instead, it usually cracks along the seams or close to the seams between the each board.
How simple it is to really repair drywall? It can become simple with practice. However, for starters, simply applying spackle (or "mud" as commonly called), does not do any good. One needs to locate where the strappings or studs are and screw the boards along the cracks and in an appropriate manner. Then, a mesh tape needs to be applied, we prefer the pink heavy duty mesh tape, which is not cheap, but helps prevent cracks even further. Then, apply 2-3 coats of mud properly, with an 8-10 inch drywall putty knife and at least 16 inches wide, to prevent bumps and to blend in with the surrounding surfaces. It needs to be as smooth as possible because you will need to wait for it to dry to then be able to sand it into a fully smooth finish. If the existing surrounding finish is textured, then you would apply a textured finish to match with the old finish on your wall or ceiling.
As a reminder, drywall repair can be very messy, especially when sanding. So, make sure you cover and protect the work area before doing anything else. If you don't want to deal with the mess, contact a professional plasterer to take care of the problem for you. Contact Boston Plastering to assist you.
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