Sinking Concrete Floor (Subsidence?), How To Repair?

I'd be very grateful for advice on how to solve a problem i have with my Hallway Floor.

My house is 30 years old and the front is on a slope.
At the point where my driveway meets the public footpath, it appears that the driveway has risen, leading me to suspect that the driveway is sliding down the slope.
This is what leads me to suspect that the fill underneath my Hallway floor is settling or sliding away.

I want to tile my hallway floor but am worried that the floor is unstable.

Frequently when i enter or leave through the front door and step on a certain part of the floor, i hear a distinct 'clunk' sound and get the feeling that the floor is giving way underneath me.
There is a crack on the floor near the front door, extending about a metre into the hallway.

I'm afraid theres a hollow area underneath the hallway floor that allows the floor to drop when stepped upon.
If the floor has movement in it, then i can't risk tiling it as the tiles would probably break due to the movement.

What can i do to accurately diagnose the problem & fix it?
Will i have to dig up the floor & replace it?
Is there any other solution, eg drill through the floor in several locations and inject something down into the hollow area (if it exists)?

I don't have any construction experience, just a bit of diy, so please excuse me if i've made a poor job of describing the problem.

Thanks in advance for any advice.

If you have insurance then the first thing to do is to notify your insurers straight away. These unexoected big ticket items are what insurance is for. A claims assessor may be of assistance but I would not agree to pay them a percentage as the costs of remedying subsidence are very large. If you try to fix it yourself you might prejuduce your insurance cover. Some insurers are engaging builders directly to carry out the remedial works. That would be a good result for you.

Hi bagel,

I don't know what your insurance may or may not cover, but I think the main investigator is likely to be a Consulting Civil and Structural Engineer [that's one person BTW], who will assess the overall structure for signs of settlement as well as advise on what investigative and remedial measures may be required.

It is useful to have taken professional advice in such matters BEFORE contacting the insurance company [see below].

I'm not going to fill your head full of fears, but "hollow" sounds usually signifify voids on the other side and the last place you want a hollow sound is the floor.

While underground water movement can wash away fines in the soils and develop hollows, leading to settlement or subsidence, this is seldom occurring in a vacuum and usually relates to a wider issue of groundwater movement or slope degradation.

This is not unusual in houses built on sloping sites in older estates - say 40-50 years +.

Remedying settlement may go far beyond any expense of tiling.
Field drains, soakaways and/or attentuation chambers may be needed to regulate the flows of water on and through your site, some or all of which might need planning permission

All this, should be addressed in a clandestine manner IMO otherwise you risk "scaring" the market against people selling on in the area.
This is not to suggest any manner of cover up, but to ensure that you deal with any information release by having retained professionals to address the matters arising in a competent manner.

We have worked with the following engineers on private house works, investigative work and/or insurance claims in the past.

Paul Downes
http://www.downesassociates.ie/

Joe Behan
[broken link removed]

Frank Moran/Noel Dillon
http://www.maloneoregan.ie/

For the avoidance of doubt this may not be taken as a recommendation but as a statement of fact.

FWIW

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.

Thanks for the advice

You're very welcome Bagel.

You'll see movement even around estate roads and footpaths after prolongued rainy seasons, particularly on sloping sites of hilly sites, too.

Normal enough and in Ireland its seldom critical, but in individual houses it enough to cause concern and apart from cracking may lead to water ingress or rising dampe.

Your building professional can advise you on these matters and others that may affect your dwelling.

ONQ.

[broken link removed]

All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.