Have just had Jh plastering services Ltd to come and completely re plaster my small room. Jack informed me if I blocked up the air brick, it could lead to excess moisture building up. He gave me a great recommendation for a alternative. Reasonably price, works clean and tidy. Really smooth finish, really happy with Jack and Chaz work, will be inviting them back for my next project. Jh plastering services Ldt 07877805665 Peter