Damp under my floor!

[tell80]

OP,
As I mentioned earlier you have True Dry Rot.
Mushroom smell is often a first indication of concealed Dry Rot.
Lack of through ventilation will create favourable conditions for the fungus to take.
Given time the infection will spread about the property seeking fresh nutrition.

You would be well advised to lift all the flooring and joists to get a clear view of the situation before thoroughly cleaning out, and then spraying.
With the flooring lifted you will also have better access to deal with any through ventilation.

Anyhow, its up to you. I've got to get back to work.

 

[jeds]

Couple of things to consider;
- photos of external
- are the walls brick or stone?
- are you looking for a stop-gap solution or a one time only solution?
- how much work are you prepared to do?
- what is the white spongy/foamy looking stuff in the photos?

 

[Nige F]

You appear, from the hazy pics, to have a serious infection of true dry rot.

hyphae or hyperbole - you can't tell with tell