Sagging creaking floor

[EternalArianne]

My house is a 1920 mill house with a bathroom/laundry added later (not sure when). The floor in the laundry room has started to sag and creak when stepped on. I went under the house and the floor seems straight and sturdy, so I suspect there are multiple floor layers and there is a gap between them causing the top layer to sag.

What would be the best way to fill in the gap between the floor layers without tearing everything apart? I had an idea of maybe drilling a small hole and spraying some of that expanding foam in there but you have to wait 48 hours for it to full cure and we kinda need to be able to walk on it since it leads to the bathroom...

[lirankoren]

If the gap between your baseboard and tile floor is ¼-inch or smaller, it should be filled with caulk. If the gap is larger than this, it's best to install shoe molding to hide the gap. When caulking gaps between your floor and tile, it's essential to use a paintable caulk.

Your Regards
Liran Koren
Real estate pro and co-founder of Luxury Property Care

[EternalArianne]

I figured out the problem. The joist supporting the floor has come loose on one side where it connects to another joist. I'll hafta Jack the house up and reattach it from underneath...

[handyandy]

You’ll probably have some cleanup after you do. glad you found it! Sounds like something that would have become worse.

[EternalArianne]

I got the joist jacked up and reattached with a hanger, the old nails had broken off entire which is why it dropped. The floor still creaks because it's just old but at least it's stable now.

[livingwithwhite]

In order to close the gap between the wooden surfaces and stabilize your floor, long nails can be driven straight into the beam.