I bought my newbuild house a month ago, and soon after completion I noticed green bricks and mortar at ground level. The builder said this was from wet leaves which had blown against the bottom of the building over the winter (they had since been removed) but he sent a man to clean it off. I now have a lot of efflorescence (chalky white residue) on the walls, not just at the bottom, but the mortar at ground level is starting to look green again. The bricks don't yet seem green. The house seems very warm and in so many ways much better built than many new homes, but this issue is worrying me. The house came not with certification from NHBC but from BuildAssure, and I understand I have only three months from completion to raise an issue about anything like this. Can anyone help?