Hello, all appreciate it if you could help me out:

So recently, some parts of the plaster and paint of the internal walls in our newly built house (2019) are breaking down with flakes and brown/black patches. I suspect rising dampness to the problem but I need to get this checked by a professional. It got pretty bad to the point where some wild mushrooms grew on one of the walls!

The sight of those brown/black patches and crumbling plaster is an eyesore and more than that we are very much concerned about the long-term effects on the overall structure of the house as well. We spent quite a fortune building this house, and it is heartbreaking to see things like this happening when the house is not even a decade old. Tried claiming the warranty to get this fixed but the company that built our house is saying this and that and avoiding our calls now.

If anyone can recommend me some good places that know how to treat rising dampness, I would be grateful! Or even any advice if you have had a similar experience.