We've recently had a garage extension built to the side of our bungalow. This included having our bedroom extended by a metre. In this new section between the bedroom and the garage I keep getting green mould appearing on the skirting board. It's only been in a few weeks. I hired a dehumidifier for a week to dry out the building work but the mould has come back where i used bleach to get rid of it initially. The damp proofing has been done correctly and we didn't have problems like this before. I'm wondering if it is the skirting board itself and where it wa stored before it was put in. Also the skirting was put on before the top layer of concrete was added in this metre wide section... This extension to the bedroom is to be a built in wardrobe so I need to get this sorted before I put in the shelving. Any thoughts appreciated.