This is a UK house build around 1900. The ground floor room had no flooring or carpet, just the subfloor was exposed. We decided to decorate the room with wood laminate flooring with an underlay and new paint. Few days later we observed signs of damp near the bottom of the walls, this has only increased over the last 1 year.
Why could this be happening and how can this be stopped? It has only appeared after we put in the laminate flooring, we thought it might go away after a while once the building gets use to the changes (flooring and underlay with new paint) but it has not.
This is on ground floor. The damp appears on only internal walls. The underlay is a Silver Underlay for Laminate Flooring which came as a rolled up mat. Thus, it is clear that the underlay traps moisture. There is no dry wall, these are more than 100 years old masonry walls. Yes, there is plaster on the walls.