Good morning, Jim

I looked through your photos, and although the photos don’t really provide sufficient information to conclusively rule in or rule out whether the material is mould, they do provide a wealth of information, and my take on it is a little different.

1) The white material was on the boards when the boards were installed during construction.

2) If the material is mould, no growth has occurred after construction.

3) Cleaning of ANY kind would not be recommended.

4) I would definitely not recommend the application of bleach.

5) Obviously the area of “contamination” has not changed since the time of construction, and therefore the situation is stable.

Cheers!
Caoimhín P. Connell
Forensic Industrial Hygienist
Forensic Industrial Hygiene

(The opinions expressed here are exclusively my personal opinions and do not necessarily reflect my professional opinion, opinion of my employer, agency, peers, or professional affiliates. The above post is for information only and does not reflect professional advice and is not intended to supercede the professional advice of others.)

AMDG