How to level a depression in concrete?

[tts1980]

Hi everyone, new to the workshop and DIY. I started replacing the carpets in my house with floorboard but one of the room has an area about 50cmx50cm that is about 10mm lower than the rest of the area. I suspect it might be due to the shower and bath in the adjacent room. It also has some cracks and looks like some patch work done previously. The patched area sounded a bit hollow when knocking on it. I am thinking of using a similar process to this to level the area https://youtu.be/wV7JF8S7XcY Am I on the right track and what is the equivalent of the product used in Australia?

 

 

[Akanksha]

A warm welcome to the Bunnings Workshop community, @tts4. We're delighted to have you join us and hope you find lots of useful D.I.Y. advice and creative ideas for your home improvement and garden projects. 

Thank you for your question. Our resident D.I.Y. expert @EricL will be happy to assist as soon as he can. In the meantime, let me tag some of our helpful members @TedBear, @Adam_W and @ProjectPete to see if they have any thoughts. 

Akanksha 

[EricL]

Hello @tts1980 

My apologies for the late reply, thank you for sharing your question about how to level your concrete. I suggest using either Dingo 20kg Self-Levelling Cement or Dunlop 20kg Ardit Floor Leveller. It's ideal for levelling concrete floors before laying tiles, carpet and vinyl. It can be applied up to 25mm thick in one application. It is possible to apply more, but you'll need to do it in sections and wait for the first level to cure.

Generally, you just add water to the self-levelling cement and mix it to a pourable consistency. It will have instructions on the bag on how much water to put in. Once it is fully mixed you can pour it into the depression where you can feather the edges of the mix with a trowel so that it finishes nicely with your existing floor.

Here is a link to our best advice: How do you level a floor?

If you have any other questions we can help with, please let us know.

Eric

[TedBear]

Hi @tts1980, although the advice on how to level has been given, I would be hesitant to proceed without first finding out why it is sinking.

You've noted that just patching over the problem has been tried and now you need to do it again.

Whenever a problem comes back it is a sure sign that we are just "fixing" the symptom and not fixing the problem.... and it will likely come back yet again.

I recommend that you carefully break up the sunken area and see what is going on under there. There could be a broken pipe leaking water and unearthing your floor. But whatever it is, it could just get worse if left unattended.

[tts1980]

Hi everyone, thanks for the advice. @TedBear good point, I wonder if there are devices that can detect leaks without having to break up the sunken area, would those be able to tell if there is a leak? Thinking of those device a building inspector would use. Or would the concrete be too thick for those to function?

[EricL]

Hello @tts1980 

That's a really good observation raised by @TedBear. However, instead of purchasing an expensive leak detection device that you'll only be using once, I suggest engaging a professional leak detection service. They will probably have comprehensive devices that will allow them to determine if you have a leak in your concrete floor.     

The good thing about engaging a professional service is that they will probably do a thorough investigation as to how far the leak goes. They will then produce a report and a recommendation on how to repair it should there be a leak. You can then use this report with your insurance should you wish to make a claim.

Please make sure to ask for references before engaging the leak detection services and always check their company reviews online.

If you need further assistance, please let us know.

Eric

[Noyade]

Hi @tts1980 

"has an area about 50cmx50cm that is about 10mm lower than the rest of the area."

On the photos, to my eyes, the patch level looks OK, but to the right, there seems to be a significant hollow in the slab? What height is indicated here?

[tts1980]

Hi @Noyade , that is around 18mm compared to the other spots which are around 10mm. So about a 8mm difference between the deepest section.

I was also wondering if there had been a previously leak that was repaired hence the rectangle hollow sounding patch next to the depression. Maybe it was too late when the previous owner got to it.

[tts1980]

Hello @EricL ,

THanks for the advice. Yeah, I will have a look around for leak detection services. Still checking with my body cooperate to see what the insurance covers. Seems like even though there is exploratory works coverages, they have protected themselves by listing a whole bunch of situations they wouldn't approve the claim (e.g. damaged to corroded pipes, building movements, earth movements, etc).

[tts1980]

Hi @EricL I got the leak detection services to do a inspection and they said there isn't any leak anymore so the issue could have been fixed previously. With the levelling compound,would I need to prime the concrete subfloor first?