Dip in floor installed over joists (no subfloor)

Q: Hi. We had the original hardwood floors in our 1930 home refinished a year ago. We now have several soft spots where part of the 2in strip has cracked and is pushing into the subfloor. But there doesn’t seem to be subfloor. The crawlspace is really skinny in these areas, so I am hoping for a solution that doesn’t involve fixing from underneath.

A: It certainly sounds like there is a dip in the sub floor beneath the strip. You could drill a tiny hole and squirt some expandable adhesive into the hole. It will seep under that strip and expand to fill the void. Bostik Findley makes a product just for this. Best place to start looking would be a local wood flooring retailer.

Follow-up Q: Sorry, I wasn’t clear in my original message – there is no subfloor. It’s a house from back in the era where the hardwood was the floor.

A: Oh, ok. I’ve only seen this type of installation a few times. Floor installed directly to the joists. So, brand new it would have been at least 3/4″ thick. The ends of the boards in question then stop between the joists. Short of having a way to fix this from beneath you would have to remove and replace at least the boards in question, probably a few surrounding. Perhaps these floors have been sanded several times over the years, eventually weakening the boards in question.

Second Follow-up Q: Thanks. Time to slither under and try to reinforce from below.

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