Fixing "hollow" section in engineered wooden floor which wasn't properly glued down

[alligatorlizard]

Long story, but to try and make it as brief as possible: had engineered wooden floor fitted recently throughout house, in one room there is a large spot (about 3 x 3 feet) which sounds hollow if knocked on, and floorboards visibly move (sag slightly) when walked on. Boards are tongue and groove, and glued down, but in this spot, I'm guessing insufficient glue was used. Underfloor was freshly laid on solid concrete and consists of: 1 thick layer of leveling compound (as concrete was very uneven), then a DPM, then a primer, then another thinner layer of leveling compound. All looked pretty level to me after this was done, and I think very unlikely to be a damp issue due to all the underfloor layers and the fact that I noticed this "hollow" patch straight away. Which seems to indicate it has to be a glue issue?

Job was a total nightmare, multiple problems/delays, insane levels of mess (DPM and leveling compound splashed all over walls and doors, damage to door frames etc etc.) - hence have weighed the possibility of asking the same floorer to come back and sort out his mistake, and decided it's probably best to cut my losses at this point, either try and fix it myself, or find someone else to do it.

Bit of research suggests glue "injection" to problem area is one solution. Does this sound like the right thing to do, or are there any other options? And would that work on an area several feet square? Obviously ripping up the entire floor is the last thing I want to do.

And am I correct in thinking that this is not something I can just ignore? e.g. would cause more damage to floor over time?

Any advice much appreciated!

 

[crazydaze]

How much is the floor flexing? Is it noticeable when you walk on it or is it more a visual thing from a distance away? Is there any noise when you walk on the area like a 'clicking' for example?

 

[alligatorlizard]

How much is the floor flexing? Is it noticeable when you walk on it or is it more a visual thing from a distance away? Is there any noise when you walk on the area like a 'clicking' for example?

It's only noticeably flexing when you walk on it - if you look at it from close to floor level, the boards in this area dip just very slightly when someone treads there. Otherwise, they seem level when no weight is on them.

The feel is noticeably different too - totally solid elsewhere, but as soon as you walk on this bit, you can feel underfoot that it's a bit "spongey".

And yes, there is a faint clicking noise.

 

[Lower]

I had a similar problem with engineered laminate where the floor wasn't flat enough. I was able to drill holes in the floor in areas that were going to be concealed by kitchen units and inject expanding foam which worked really well. But you need to create a number of holes to squirt it through. So you end up accepting the least worst of the two options.

 

[alligatorlizard]

I had a similar problem with engineered laminate where the floor wasn't flat enough. I was able to drill holes in the floor in areas that were going to be concealed by kitchen units and inject expanding foam which worked really well. But you need to create a number of holes to squirt it through. So you end up accepting the least worst of the two options.

Yes, holes in nice new floor definitely not ideal! But still preferable to having to rip up floor and redo it. What did you fill your holes with? Presumably you can get wood filler in a variety of colours - or could the holes even be filled with thin dowling?

 

[Lower]

My holes were hidden behind kitchen units, but depending on the type of flooring you’ve got, I’m sure there would be ways of disguising the holes

 

[alligatorlizard]

My holes were hidden behind kitchen units, but depending on the type of flooring you’ve got, I’m sure there would be ways of disguising the holes

Fake moustache and glasses maybe