How to tile over exposed aggregate?

[Wei123]

Hi brainstrust,

Long time observer, first time post. Recently hit a roadblock with our exposed aggegrate patio and am getting very confusing advice from various trades. 

Long story short, we moved into this property with a large concrete area however the exposed agg must be quite worn as it was very sharp to walk on and my kids would cut themselves badly if they tripped. We had it honed back but unfortunately it came up very patchy and we were told it was due to the age of the concrete and the high ratio of rocks vs cement (see images). Sadly with that money down the drain we need to find another option to resurface it. We're considering tiling it but after seeing the labour costs we are mulling the idea of DIY. It's a large area (65sqm plus the rear pathway) but it is relatively flat I believe and square-ish, and has already been grinded back i.e. any previous sealant has been removed, which I understand is necessary if adhesive is applied for tiling.

The concrete I believe is over 8-10 years old. There is one big crack in the rear pathway but small fractures in the main alfresco area. Relatively flat in most areas after going over with a spirit level.

Questions:

1) I'm generally handy and have done floorboards in the past (and maybe 15yrs younger), are we insane to consider to take this on as a first time DIY tiling project?

2) Confirming that it is okay to tile right over the exposed aggregate with suitable adhesive mix?

3) Are 10mm thickness tiles strong enough to apply? Noting not all the exposed aggregate is completely flat (see images)

4) Considering 600x600 tiles, what pattern should they be laid and which corner do you start from?

5) I went into Bunnings and was told all their tiles are not suitable for outdoors, is this correct? Referring to the Duratile 600x600s.

6) What do I put on the edges to finish? Metal strips?

Thanks in advance for any advice!

Cheers,

Wei

[Wei123]

Thank you @Nailbag and @EricL 

Appreciate the recommendation. Not sure if you can see from the photos but on the exposed aggregrate the rocks are quite high compared to the cement level i.e. well exposed to the point where I would say some areas would be greater than 6mm depth. This would mean the adhesive material would be thicker than this when applied. This being the case, I feel perhaps the leveller needs to be applied across most of the area where it is not flushed, and use a thinner layer of the leveller, or, use an alternative adhesive that allows for a thicker bed?

I note from a previous post of yours @EricL that you recommended:

https://www.bunnings.com.au/davco-20kg-ultraflex-ceramic-tile-adhesive_p6656384

Would this be a more suitable alternative? Cheers.

Thanks again.  

[JacobZ]

Hi @Wei123,

The problem with using just tile adhesive to account for changes in height is that you won't get even coverage underneath the tiles. Once the tiles are pressed into place, the adhesive will spread out, so you might have 4mm of tile adhesive under one part of the tile and 12mm under another part, which really isn't great practice.

Assuming you are using ceramic tiles, either the Dunlop Resaflex or Davco Ultraflex would work as long as you follow their instructions closely, but you shouldn't rely on a thicker bed being the solution to the gaps between the aggregate.

You would be far better off using the self-levelling compound to smooth out the differences in height, then set your tiles in place over the top of the levelling compound using a suitable adhesive for your tiles. As @MitchellMc mentioned, you should use it to pour through the depressions caused by the exposed aggregate, but don't cover the whole patio as it will level and take away any slope from the concrete. 

In my initial post, I should have said "flat" as opposed to "level". Apologies for that.

Let me know if you have any further questions, I am happy to help if required.

Jacob

[Wei123]

Thanks @JacobZ 

I had a closer look at the Davco Ultraflex, and it recommends 12mm max for tiles greater than 400x400. Would I then apply 6mm on the ground and 6mm on the tile?

The Davco Ultraflex recommends putting a primer down first, is this necessary? If so, could you please recommend a suitable primer for my exposed aggregrate? Thanks.

Prior to applying leveller in select areas, would a primer still be required before applying leveller?

Cheers,

Wei

[EricL]

Hello @Wei123 

The instructions for back buttering were very general, but it did mention to apply a thin covering only. It would be best that the majority of the adhesive be applied to surface rather than the tile. Remember to follow the installations instructions especially how the tile needs to be moved into position. 

I propose using the Lanko 1L Ultraprime 124 Surface Primer as this primer can be used with self-levelling products as well. This primer would need to be applied to the area where you'll be using the leveller.

If you need further assistance, please let us know.

Eric

[Wei123]

Hi @EricL - Thank you for that. Would you mind also recommending a grout? Is there only one type or should there be a particular grout that has flexibility too like the adhesive?

@JacobZ - regarding your suggestion, "For changes in direction, like the pathway down the side of the house, adding a strip of different, smaller tiles to create a breaker strip will allow you to adjust the layout to suit the change in direction." - do you have an example of what this looks like?

Thanks all!

[JacobZ]

Hi @Wei123,

I couldn't find a great example so I used AI to generate something. It's a little bit wonky, but it shows the general idea.

The idea is that by adding a breaker strip, you can transition from one layout to a different one. With the breaker strip separating the tiles, it would not be such a big deal if the tiles were misaligned slightly from the patio to the pathway.

For grout, I'd suggest using Davco Sanitized® Colourgrout in a colour of your choosing. To increase the flexibilty, you can add Davco 1L 4 In 1 Grout Additive to your grout mix.

Let me know if you have any further questions.

Jacob