Fixing spongy spots on an engineered wooden floor

[landahoy]

Hi All,

We had an engineered wooden floor installed a while back. It was installed on top of a concrete floor and some thin insulation/underlay. The concrete floor it was installed on wasn't perfectly flat everywhere and as such there a couple of spots that are slightly spongy when stood on (there is plenty of room between the floor and the walls - its definitely the concrete floor flatness). I have seen youtube videos of a fixing technique by boring very small hole and injecting in various products ranging from glue, to epoxy or expanding foam. However i'm not sure i can do this because the floor is on top of insulation layer. Is there any genius diy expert out there who could advise me what i could do!? Has anyone done this in a similar scenario?
Thanks to anyone who has any ideas!!!

 

[foxhole]

Had similar problem with concrete floor covered with t&g floorboards which were floating on underlay and had some hollow spots. Drilled thru to concrete and inject foam fixing adhesive, covered problem area with buckets of water to hold down as tight as possible. Was surprised and happy with how well this worked . With engineered floor I would use a plug cutter for holes so it can be made good, but repair won't be invisible.

 

[landahoy]

Thanks for replying Foxhole. I'm more assured hearing someone has actually tried it successfully. Out of curiosity did you use a syringe or similar to inject the foam? Any other tips when it comes to doing it?

 

[foxhole]

Foam gun has flexi tube.

 

[big-all]

just to correct foxies plug cutter comments
i think he may mean
use a matching countersink bit and plug cutter set with the plug taken from an off cut or hidden area
but could off course be very wrong

 

[foxhole]

just to correct foxies plug cutter comments
i think he may mean
use a matching countersink bit and plug cutter set with the plug taken from an off cut or hidden area
but could off course be very wrong

Correct.

 

[chappers]

seams a bit severe to be drilling holes in a brand new floor. Did the installer not advise you that the existing floor needed levelling.