hallway floor problems

Hi I live in a council house and we want some flooring in our hallway. We are not sure yet what were gonna have but either be vinyl laminate or tiles. The house currently had tiles in the hallway laid on top of some other small orange tiles. The proper tiles were dipping near entrance and in few other places and sounded hollow when knocked so we told the council that we want to put a new hallway floor but the floor dipps. They were gonna come out and do self levelling now as I mentioned some tiles were loose and I dont want self levelling over the proper tiles the were loose so I lifted them to discover the small orange tiles. Now they never came on the day to do the job so I started to look at orange tiles which were also dipped in the same area also sounded hollow when knocked.

My question is what is causing this?
What's under the orange tiles?
Can self levelling be laid over this and be ok?
What is really needed as we don't want problems in future?

Now I know on this part of forum its not for tiling but I weren't sure if its a tiling issue or ground issue therefore I shall also post in tiling section.

Also I have included a pic of the orange tiles in my hallway any help would be great

Depending on the age of the house they are likely to be laid either onto concrete or directly onto the soil (for very old houses). They are quarry tiles and you can self level over them and tile on the top, but only if they are solid - which doesnt sound like your case.

I'm afraid it sounds like you'll end up lifting a few to see whats underneath. Its possible that they are laid over a floor that doesnt have a functional damp proof membrane, and if thats the case you'll get damp coming through - either way its best to know before you spend case tiling over the top

Think the house is 70 80 yrs old. I agree the quarrys are not solid . Il try lift a quarry to confirm if soil or concrete. Will the dpm be the first thing I see if one is used. What would it look like and where would it be positioned and how deep. Thanks again for your help and advise

Unless the floor has been re-screeded in its lifetime then its very unlikely to have a DPM. it would be under the concrete - if you find any

Thanks for the help and advise do you know why the quarry have dipped and sound hollow in areas

As above.

Remove a piece of skirting and see if a membrane has been lapped a few inches up the wall - nothing there would indicate no DPM below the concrete.

Check for damp signs in the walls and skirtings.

Hollow tile and floor dips might need further investigation )as above) - its your call but doing a professional job we always get to root causes and remedy them. No call backs.

Its likely that whatever they are laid on has dipped\broken and sank, leaving some tiles with not a lot under them. the cause of that could be any number of things and your not likely to be able to guess at it i'm afraid

It seems like that you'll have to lift a few to see and what underneath it. I might agree with that whatever they laid on might've broke and sank. This article https://www.electrodry.com.au/budget-reno-our-top-tips-for-tile-and-more/ might aid on renovating on a budget.