We are often asked why new plaster often cracks. This is annoying, but completely normal. Often, you have friends trying to be helpful who say your plasterer hasn't used scrim tape on joints but even using scrim tape is no guarantee that cracks will never appear. Colder months are particularly bad with the excess of moisture in the air and plaster boards can swell up a bit so when you pop them on walls in a warm dry house, they will dry out and shrink and cracks may appear. These cracks are completely manageable though and a good builder (like Transcore) will advise you to call them back after around six months to fix the problem leaving you with pristine, smooth walls.