Can you tile directly onto a concrete slab?

[demoreno]

Hi all!  First post…

Looking for some advice on indoor tiling.  Multi level townhouse on concrete slab, built approx 2010.

We’re planning on tiling the entrance hallway and adjacent laundry with 600x600mm tiles.  Reading various sources online, I’m seeing a lot about “crack isolation membranes” - is this something we’ll need?  Or can we simply tile directly onto the slab?

Any/all advice welcome!

[MitchellMc]

Welcome to the Bunnings Workshop community @demoreno. It's wonderful to have you join us, and many thanks for your question about tiling over concrete.

Are there any expansion joints in this concrete slab or cracks where it has seen movement? If not, then you can tile directly onto the slab. New concrete needs to be decoupled from tiles as it shrinks with time and can crack. But if your concrete has been there since 2010 and it's sound, then you are right to tile straight over it with Davco 20kg Grey Ceramacrete Tile Adhesive.

Crack isolation membranes are something that is used extensively in America; their use here is just in specific circumstances.

Here's a handy guide on How to lay floor tiles.

Please let me know if you have any questions.

Mitchell

[demoreno]

Mitchell, thanks for the super quick response!

Once I’d posted I realised I’d missed some details, but of course forgot again by the time I was back online… 

It’s a waffle slab, about ten townhouses in a row, I assume on the same slab, as they were built all together - there may be joints inbetween houses, unknown.  The concrete in our place has a few hairline cracks through it, but nothing of concern I don’t think - this is where I confused myself about the crack isolation membranes though, as to what “counts” as a crack of concern.  And yes, the membrane info I’ve encountered is from US sources.

So I guess I have two more questions:

 how big does a crack have to be to be an issue / do I need to fill or isolate hairline cracks at all?

- what makes you suggest that adhesive vs the other options?

Thanks again, much appreciate the help!

[DCS]

Hi and welcome,

The short answer is yes, you can tile directly onto concrete.

As mentioned in previous comments here, movement is something that needs to be addressed. Green slabs (less than 12 months old) will continue to move until fully cured and settled. Seeing as your slab was laid in 2010, this should not be an issue.

You need to check for expansion joints in the concrete, usually 6 metres apart. if your entry is a small one like mine you'll have no issues tiling straight over the slab. If you do however have an expansion joint, you will need to set up your tiles so that the tile joints lay directly over the expansion joints and instead of just using a grout, use a flexible sealant of the same colour as your grout. Following this should ensure a long life for your project.

[EricL]

Hello @demoreno 

That is spot on advice coming from @DCS, if your slab is more than 10 years old any movement that might have occurred has definitely happened. Surface cracks on your slab will naturally happen, it only becomes a concern if the cracks get bigger and parts of your slab goes lower in a short span of time. 

However, if the cracks have been there for more than 10 years and the slab has not moved since, it's safe to say that the slab has settled well and truly into the ground.

The Davco 20kg Grey Ceramacrete Tile Adhesive is formulated for rigid substrates like a concrete slab. The adhesive will dry hard and will firmly anchor the tile to the concrete. This type of adhesive is used for stable surfaces where there is very little movement.

If you need further assistance, please let us know.

Eric

[EricL]

Hello @DCS 

Thank you very much for sharing your knowledge about concrete slabs. I'm sure @demoreno will find this information very useful for their tiling project.

Eric

[DCS]

Personally I used the Davco Ultraflex Ceramic Tile Adhesive for 90% of my tiling applications, both indoors and outdoors. The reason is because it has a rubberised flexible bed even when cured to allow for any small movements with either concrete or with fibre sheeting...

[demoreno]

Sounds good, thanks!

And thanks more generally to everyone in thread - @EricL is spot on saying it’s all useful info for me - other than prising the old tiles off (they’re determined to stay stuck!), I’m all set to go

[MitchellMc]

Keep us updated @demoreno and reach out if you need further assistance or get stuck. 

If it's a large area, it might be worth investing in a rotary hammer drill. On the chisel function, it will have the stubborn tiles popping off in no time.

Mitchell

[demoreno]

I’ve just ordered a rotary hammer drill for click & collect tomorrow - congrats on the sale!

(wasn’t a hard sell, let’s be honest - next door neighbour doesn’t have one either & encouraged me too - we have a bit of a tools library going on)