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How to level sections of concrete garage floor for laminate?

Hey Team!

This is a meaty one - thanks in advance.

So, I'm in (what I certainly hope) are the final stages of a garage conversion.

I've framed, plastered & painted. I've purchased Floating Floor which according to their specifications already has a 1MM EVA underlay layer... Though it also recommends adding a poly-film between the concrete and laminate - so I was planning to use this although would've preferred not having 50m of it!

The floor is 10m x 4m and (in most places) is within the specs the manufacturer requires for level and slope.

There are 2 places however that are not in spec.

Place 1) There's a channel appx 3m long and <1m wide with a max depth of 15mm

--> It seems to me a self-leveler would work well here... I'd love to know what the difference between these 3 is:

https://www.bunnings.com.au/lanko-20kg-133-pro-level-floor-leveller_p0966662

https://www.bunnings.com.au/sika-20kg-sikafloor-level-pro-underlayment_p0760431

https://www.bunnings.com.au/bastion-20kg-floor-leveller_p0273642

I don't think the #1 or #3 speak to coverage, so I'd be inclined to go with #2. #3 also doesn't like to go deeper than 12mm.

#2 also speaks to 'bulking out' with aggregate to reach 50mm thicknesses - which may be useful for my 2nd Place.

The Plan

Given we're essentially just 'filling a hole' here, apply Primer, mix self-leveler, pour slowly, trowel if needed.

Wasn't going to bother with a spiked roller to remove air-bubbles e.g this particularly since I'm not overly concerned if the final surface isn't perfectly smooth, with laminate going on top.

Place 2) There's a 4m long 1m wide section along the wall, sloping downwards towards the wall at a max height of 25mm.

Based on the coverage of self-leveler #2 above, I'd imagine I might need more than 1 bag, which I'm hoping to avoid, given the cost.

My thoughts here were:

1. Use concrete @ $8 a bag and then add a light self-leveler topcoat in the event it is needed (first-time concreting, although extensive plasterer, so not my 1st rodeo on a trowel 👍) - downside being the dry-time.

2. Use some ply / MDF / OSB - downside being the risk of moisture

3. Use some cement sheet - downside being you can't easily cut it to size and that it's not particularly cheap.

4. 'bulk out' the Self-Leveler with some Aggregate maybe this one although it's not within the 1-2mm the Sika PDS mentions - any advice on how to do this? Which aggregate to use and any downsides of doing this e.g rough impact on drying time?

The Plan

To avoid splashes:

Cover the lower corners of the plaster in painters tape / drop sheet

To prevent the self-leveler running under the plaster (given that's where the slope leads):

Lay some Foam Flashing maybe this one for the extra height for the sake of $1?
Attach to the plaster with tape and the concrete with caulk maybe this one.

Apply Primer, mix self-leveler, incorporate aggregate, pour slowly, trowel.

Once dry, I'd imagine it will be worthwhile to then add a 'top layer', in the event the aggregate is visible?

1 other question relating to both pours - given the floor is on a 5mm slope overall, is this likely to affect the self-leveler?

i.e is it going to 'pool' slightly higher on the lower point? Or is there some 'minimum threshold' it wouldn't self-level over in the span of the time it takes to start setting?

My guess would've been that it's not an issue, or, that I'd very lightly re-trowel it after 5-10min to prevent it from doing this.

Thanks so much

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Comments

EricL

Hello @Will03

Thanks for sharing your question about levelling sections of your concrete garage floor.

You've pretty much nailed the differences in what you've read regarding the specifications of the floor levellers. Sika will technically do a 30mm fill in one go, Lanko will do 25 and Bastion will do 12mm. All of them more or less dry at the same rate with the same provision regarding thickness and current atmospheric conditions. Because they are all 20kg, they will cover the same amount of area at a particular thickness.

The areas you are trying to fill are quite extensive and it does start adding up when you use more than five bags of leveller. Would it be possible for you to post a photo of the areas you'll be filling in? This will give our members a better idea of its condition.

The ideas you've suggested are actually quite good. I was going to recommend using plywood or OSB. To prevent moisture damage, I suggest putting builder's plastic on the concrete surface before you put the wood over the surface. You then put another layer of builder's plastic over the plywood/OSB for even better moisture protection. If you can level it out just using plywood and OSB it will save you a ton of effort.

Using concrete is another option, but if you are pressed for time then it's not a viable solution. Masking the area with painters drop sheets or builder's plastic will prevent concrete from splashing on your walls is a great idea.

As for the rest of the plans it sounds really good. I totally agree with re-trowelling the surface just to make sure that the fall is correct. I would probably double check it with a spirit level just to be safe.

Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.

If you need further assistance, please let us know.

Eric

Nailbag

Hi @Will03 sounds like you’ve already got most of it covered correctly with that extra advice from @EricL

I recently had a job to level a 2m x 4m sunroom conversion that had a badly uneven concrete floor. It was to be tiled with small 100 x 100 tiles so a similar issue as yours needed a pretty level base. Some sections had a 20mm difference so cement sheet was out.

I went with one of your plans and used concrete to build the deepest areas to save on leveller. I used 1200 and 2400 levels to mark out these areas to concrete and applied bondcrete then the concrete screeded the areas off.

Once dried checked my low points, marked them and then applied leveller to those spots. If you make the. Mix a little wetter and use the mixing rod on a high powered drill or mixer for longer, you will hardly get any bubbles.

You only have a couple of minutes to feather out the edges with your towel then leave it. Leveller isn’t supposed to be troweled and it can result in high spots on the edges

Once poured don’t pour more on top only the edges otherwise it will creat a step. Pouring on the edges allows the leveller to do its thing best.

Nailbag

Dave-1

Evening @Will03

I really like your reasoning, it makes sense and you have stepped through what I would do. Like you I have never done any floor leveling tho @EricL's extra bits and @Nailbag's pics really make it a lot more "breathable and not stressed 🙂 " to do.

With you leveling your garage I had the same decision when I retrofitted mine, I actually had more of a fall then you do over the entire distance and considered a false floor even. In the end I just layed (Placed carpet tiles) carpet tiles over the concrete and it isnt noticible. I did have to chock the bookcases level and give them a false plinth but it came up nicely. Bookcase retrofit to create a garage library is the project.

I will be following along to see how you go with the leveling.

Dave

Will03

https://www.workshop.bunnings.com.au/discussion/comment/40683#Comment_40683

Hey Everyone (@Dave-1 @Nailbag @EricL)

Thanks so much for the advice and thoughts - Here’s an update on how it went!

Firstly, I considered the options mentioned and revisited this post - https://www.workshop.bunnings.com.au/t5/Whole-of-House/How-to-level-up-a-concrete-floor-for-laying-laminate/td-p/93234/page/2

I liked the simplicity of laying some MDF wrapped in builders plastic, but, ultimately didn’t go that way myself, for 3 reasons

MDF wouldn’t have worked out cheaper for the area I needed
It would've been a bit difficult to get the thickness 'just right'
It seemed a bit risky (in my mind, anyway) to have it ‘floating’ under what would then be an already floating floor.

Having said that – it would have saved quite a bit of time and labour!

I ended up continuing my own train-of-thought and going with the self-leveller + aggregate option.

I used the aggregate available at bunnings

i.e this https://www.bunnings.com.au/20kg-bag-of-screenings_p0760532

In retrospect, I should’ve used a smaller (i.e finer) sized stone e.g 2-5mm instead of 7mm

i.e this https://www.bunnings.com.au/bastion-20kg-aggregate-crusher-dust_p0135857

I should have done that, because even though I’d have liked the stones to be ‘layered’ a little to cover the close-to 25mm height – it would be easier to layer and smooth out stones that are smaller… and (depending on how you look at it / what tools you have handy) you’ll save work for yourself by having the stones too low rather than too high…

First I created a perimeter using a spray foam:

https://www.bunnings.com.au/parfix-340g-triple-expanding-foam-filler_p1232844

In retrospect, I should’ve gone with a silicone, since I didn’t really need as much height as this created and I certainly didn’t need the width either.

Then, I applied a primer per the instructions on the Bastion Self-Leveller packet (2:1 water / primer), spread with a broom)

Let that dry 4-5 hours with good ventilation.

Added ~20kg aggregate and spread using a timber float (something like https://www.bunnings.com.au/masterfinish-wood-float_p5961900) courtesy of my dad – an upside-down rake would probably have got it done too… Definitely need something with a bit of weight to it to help gravity flatten things out.

Mixed up the Self-Leveller for 3 minutes, used between 4.2 – 4.7 litres of water per bag in this bucket:
https://www.bunnings.com.au/fightmnd-big-freeze-10-20l-bucket_p0561833

No you couldn’t get away with a smaller bucket unless you did smaller batches, which probably isn’t a good idea, given the tight time-frame on drying.

Starting in the corner, pour slowly and worked my way out, using a large broadknife to spread:

https://www.bunnings.com.au/kango-150mm-joint-knife_p0098419

In my case, it was easy to tell if I was ‘about level’ - because the aggregate would be covered – if not for that approach, I’d have gone with painters tape on the wall to signify the height I needed to reach.

Left it overnight to set, left the A/C on 18 to keep the temp stable / maintain humidity.

After a day or two, I noticed there were a few areas where the aggregate was slightly poking up, so added one more bag of leveller following the same process.

That looked like:

I then took off the foam by running a chisel under it (had I gone with silicone, you’d just leave it!) - it achieved the goal of preventing the leveller running away.

Overall, I'm pleased with the result and the cost savings. Spreading the aggregate was time consuming though – so this might justify getting the extra bags of leveller.

Thanks again everyone

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/83694#Comment_83694

🙂 Afternoon @Will03

Love your description and the information within your post. It really was helpful in sorting out the steps and will help anyone coming along wondering the same thing! Right down to how the last nit you added. How is that last bit holding up as in bonding to the first batch?

Yeah Cheering for you! 🙂 So nice to hear that you succeded in your project. Whats the next step?

Dave

EricL

https://www.workshop.bunnings.com.au/discussion/comment/83694#Comment_83694

Hi @Will03

Thank you very much for the in-depth update. The floor leveller looks excellent, and I don't see any pebbles poking out. I'm sure this information will be very handy to those members who are planning on levelling their concrete floors.

Eric

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