Is this dry rot?

[Jordman]

We have this on the underside of a flat roof and it’s dry to the touch. Maybe from and old leak or is it dry rot?

 

[cross thread]

Looks like dry rot spores,

 

[Lower]

Looks like white mould, not dry rot. No sign of fruiting bodies, cuboidal cracking or the dry rot 'roots'.

Looks like you have a leak.

 

[^woody^]

Is the timber soft, brittle and crazed?

It looks too dense for dry rot hyphae, but don't get hung up on what species it is, it needs removing regardless

 

[Jordman]

Is the timber soft, brittle and crazed?

It looks too dense for dry rot hyphae, but don't get hung up on what species it is, it needs removing regardless

Some bits are brittle and break off easily, Im hoping it’s just from an old leak in the flat roof above

 

[^woody^]

Wet rot fungus should disappear when the damp is removed, and the timber more soft than brittle