How to smooth a concrete floor without levelling?

[OneMansFool]

Hi folks, I am interested in fixing the holes and aberrations in my concrete subflooring, but I do not wish to level it. Finding any info on how to go about this is proving frustrating because literally everything out there assumes levelling. 

The original concrete pour from the 70s is very uneven (~70mm over five or six metres), but this is still not enough to perceive or to cause me any problems. My far bigger priority is maintaining every possible mm of ceiling height in all cases. For this reason I would rather smooth the floor as is (ie fill the holes but not worry about the gradient), and therefore happily forego the warranty of the vinyl planks I put down, and avoid spending thousands of dollars on leveller I don’t want.

As you can see in the photo there are some very large holes that need smoothing over. Is some sort of leveller still the best product for this (ie can it be manipulated to stay just in the regions I want it) or would it slowly make its way to the lowest point of the floor when I leave it to set? Would another product be better?

[MitchellMc]

Hi @OneMansFool,

You'd prbably be looking for a repair mortar rather than a self-leveller if you just want to do a skimcoat to fill the depressions. I'd recommend using something along the lines of Dunlop 5kg Ardit Rapidset Repair Mortar.

The issue with patching areas and not doing a self-leveller over the entire floor is that it will be quite lumpy and uneven. This unevenness will be transferred through your vinyl planks. You might like to go for Hybrid Vinyl planks instead of adhesive-back planks, as they have an additional thickness, which will help mask the floor discrepancy.

Please let me know if you have any questions.

Mitchell

[OneMansFool]

Thanks Mitchell, that is all very helpful advice.

I certainly see what you mean about it being a challenge to get it all sufficiently smooth with just the mortar. 

I have done a few tests the best I can with some flooring samples, so I am not flying completely blind. I think with sufficient patience I’ll be able to get it sorted, thanks!

[MitchellMc]

That's great to hear @OneMansFool. Keep us updated, and reach out if you need further assistance; we're here to help.

Mitchell

[OneMansFool]

This has been going slowly but surely. While the results look a little rough in places, overall it has worked well and I believe I’ve got it all fit for purpose. I’ll share some photos shortly.

But in the meantime I have a different but related question:

Previously I had builders in to grind the floor down and to reconfigure my (brick) walls around. Now I am spot fixing any damage on the walls with an acryclic render (the same stuff the builders were using) before smoothing and then painting. But note this place has never had skirting boards and I want to keep it that way.

So my question is how best to deal with damage to the existing wall render when it sits right along the sub flooring, ie right at the bottom of the wall. I’m not worried about getting it sufficiently smooth (I’ll be able to do that), I am just wondering if I need to be especially careful to not connect the render of the wall straight onto the subfloor. Would that cause cracks down the track when the building shifts?

Is there something I should place between the bottom of the wall render and the subfloor? ie to maintain a mm or two gap which would no longer be visible once the flooring goes in?

Thanks!

[OneMansFool]

Some photo’s may make my question make more sense. I want to fix instnces like this, for example:

 

That said, I may be overthinking it a little as in other parts of the house the original render just spills right out onto the subfloor really messily. 🤷🏻‍

[MitchellMc]

I wouldn't be overly concerned about not connecting it, @OneMansFool. The only thing I would do is run some tape along the floor next to the wall so that when you add your render, the tape can be removed to assist in creating a crisp transition.

Mitchell

[OneMansFool]

Brilliant, thank you.