Mold detected in basement

[Mike Meerschaert]

Hi,

I'm looking for some advice from my fellow landlords. I have a rental property in Portland with a finished basement - I managed the remodel myself, everything is up to code, and it was completed in May 2022. 

There was recently a water intrusion event caused by a clogged drain outside which caused some hydrostatic pressure in the soil and some water came up through the slab, which the tenants promptly cleaned up and I ran a dehumidifier I rented from home depot for 24 hours. The tenants were understandably concentered about the possibility of mold growth resulting from the water intrusion, so I had a test done which detected some mold. They had a separate test done by another company which also detected some mold. I had a remediation contractor come out, and he told me the levels on the report is what he'd expect from a basement in Portland, and any amount of washing / bleaching wouldn't reduce the levels much long term as more moisture would enter the space up from the slab because concrete will always give off some moisture, and he couldn't really recommend much remediation. Also, there is no visible mold and no mold smell in the basement (there is a little on the caulking beneath a single pane picture window upstairs which I'll deal with).

That didn't sit too well with the tenants as they have been looking online and finding information about how dangerous it might be, and it didn't help that the first report that I had done the inspector attached a boilerplate message recommending a full HVAC cleaning (ducting is 1 year old) HEPA vacuum, air scrubbers, double washing everything in the unit with bleach, etc. so now the tenants are being fairly combative and insisting that more needs to be done. When the contractor was there they even came downstairs and started demanding to know exactly what steps would be taken (hands on hips, scrunched up face to give this some color). My issue is that in the opinion of the remediation contractor (who has a financial incentive to recommend as much remediation as possible) all that wouldn't reduce mold levels long term, due to the fact that it's a basement in Portland, and the levels on the report are extremely common in basements in the area where no water intrusion had happened. He even went so far as to say it's one of the cleanest finished basements he's seen. For reference, both tests detected an average of 20-30 spores per test of Aspergillus Penicillium and about 4 spores of Cladosporium if that means anything to anyone.

They also said their children have asthma and are concerned about flare ups this winter, which is really concerning to me, given that maybe my property isn't the best fit for them due to the fact that it has a finished basement and single pane windows upstairs (it was built in 1956). I decided to give them the option to break their lease and leave, if they so choose, which they haven't responded to yet.

My question is, has anyone dealt with a similar situation who may be able to give some advice on this? Would you allow a tenant to break a lease given the circumstances? And would you invest the money to do the performative deep cleaning knowing that subsequent tests would likely show  the same levels after all was said and done?