Is this dry rot?

[smalalalalalala]

Hi there

Does it look like dry rot to you?

It is under the bath. It is cheap board which was covered by cheap vinyl.

Area has been treated for dry rot in 2019 but it has been wet lately due to a leak.

We're planning to have it tested but would live reassurance.

I should add that it's all flat, no 3d.
And there is a slight damp smell.

I once bought a house with dry rot and it looked very much like those roots/tendrils in the centre of your photo. The smell was quite distinctive too.

I’m afraid it does look like it, we once bought a house ( v cheap) that had it all over the front.
I’d get the wood up quickly and burn if possible. You can buy fungicide to treat the underlying wood beams.

those white strands look like it.

How big is the area in the photo?

This needs careful attention ,remove wood a metre beyond what looks affected, bitter experience.

I think that looks more like wet rot to me.

Have a look at the pictures here;

www.agdampsolutions.co.uk/news/the-difference-between-wet-dry-rot/

It's hard to see on the photo, but even if it's dryrot, the white vein like bids are often only on the surface. Spray immediately (Permagards 3 in 1 spray for dry, wet rot and beetles is great) while you wait for test results and find the cause of the damp and stop it, and try to dry out walls/timber (cross ventikation), but don't panic. Dry rot cannot attack wood that is dry (less than 20% moisture), so unless your entire house is soaked you don't need to worry about any horror stories that the dry rot is spreading through your house and is destroying everything. Dry rot is usually very contained and the cause is usually trapped moisture from a localised water ingress like leaking downpipe etc.