Can I lay pavers on exposed aggregate?

[3ltiffo]

I have some very hot exposed aggregate for a pool deck (no coping and all) I’m hoping to lay pavers over it (height clearance isn’t an issue as fence needs replacing too) is this possible? Will I have an issue with water logging or cracking? Does the aggregate need to be ground back first or can I use the rough surface? The aggregate is in good condition. What is the best type of adhesive? Mortar? Something more water friendly/flexible? 

[StevieB]

Welcome to the Bunnings Workshop community @3ltiffo.

Let me tag @Adam_W, @TedBear and @Jimi to help kick off this discussion. Our resident D.I.Y. expert @MitchellMc will also be happy to help when he's back on the site on Sunday.

Stevie

[TedBear]

Hi @3ltiffo , it is possible to lay pavers onto the surface, (pressure clean it first) but you would be best to use an adhesive. A mortar layer that is strong enough will add extra height and the extra height will add leverage from the top of the paver, down to point of attachment to the existing surface. This means that with the bumping, twisting, etc, that happens to a floor surface in normal use, the mortar layer will be stressed and could eventually break away.  An adhesive will allow for a thinner coating to be used and also have the ability to withstand movement without breaking away. (In other words it provides a better interface for use with movement.)  You will need to use a suitable outdoor grout to keep water from seeping between the pavers (as there will be nowhere for it to soak down into) and it will help to keep the pavers in place. Using sand between them won't be a good choice.

You say that heat under foot is an issue.... what sort of pavers will you be using? 

Normal brick pavers may be just as hot as they will absorb heat over time. Perhaps you have looked into suitable pavers already for low heat absorption characteristics?

Have you considered using non-slip tiles? ... some are better than others at not absorbing heat but best to discuss that with a tile supplier to get the right ones.  Tiles will add less height and therefore the destabilising stresses on them from walking, twisting, etc is less than is caused to higher-sided bricks. ( i.e. less likely to be worked loose.)

[3ltiffo]

The dream would be travertine tile but the cost for our area would be some 20k which I cannot justify. So hoping for travertine pavers. Living in qld I have come to terms with the ground being hot but the unsightly yellow will never be okay with me! (I want it to be a clean off white colour)

do you have any recommendations for adhesive? Or grout that may be suitable? 
thank you so much for your comprehensive reply! 

[MitchellMc]

Hi @3ltiffo,

Welcome to the community. It's awesome to see the knowledgeable @TedBear has been assisting you. 

I've been taking a look at some of our exterior tile adhesives to find one that would be suitable for adhering to Pebblecrete. I've come across this document from ARDEX (one of our tile glue suppliers) where they discuss the preparation of Pebblecrete and why it isn’t acceptable to apply materials over these finishes. ARDEX recommends the best way of dealing with ‘Pebblecrete’ surfaces prior to the application of levelling cements, ceramic tile adhesives and membranes is to remove the material from the surface via mechanical methods.

The issue is that the tile adhesive will have trouble adhering to the epoxy, binders and sealer used in the Pebblecreteing process.

This doesn't mean that you can't glue tiles to the Pebblecrete, it's just that our manufacturers don't recommend it.

Please let me know if you have any questions.

Mitchell

[Adam_W]

Hey @3ltiffo , I can understand your desire to cover that pebblecrete. Not a fan myself & it can get so slippery.
Excellent advice from @TedBear & @MitchellMc.
My only concern is that pebblecrete has a tendency to 'bubble', lift away in sections, especially when moisture penetrates behind it and breaks the bond with the substrate.
Installing pavers & relying on the pebblecrete as a firm substrate has the potential for problems down the track as any pavers above a 'bubble' would become loose and if they came free would take the pebblecrete with them.
As much as it's a chore I don't feel there's a quick & easy way to do this project. If you're planning on being there for the longer term I'd be looking at stripping or grinding back that pebblecrete to then use adhesive to fix your pavers. 

Other option of-course would be to just remove the pebblecrete to about 1m back from pool edge, lay travertine there & then create a floating deck over the other section?

[3ltiffo]

Thanks for the reply Mitchell, I’m not looking at tiling though. I’m looking at paving as it’s much cheaper and doesn’t require grinding the aggregate down. 

[TedBear]

Well @3ltiffo you have opened up an interesting discussion for consideration. I had a look at the document @MitchellMc referred to and @Adam_W 's concerns. I guess it's now up to you to consider the risks and benefits. If you adhere bricks over the area (as is) and attach them to each other by grout, then they should form their own strong complete surface, such that if some of the pebblecrete were to loosen below, the top surface would still be safe, viable & unaffected. But I haven't tried this, so that isn't any guarantee. At worst you could repair a loose section later anyway, since bricks are individually removable and easy to get replacements for.

My only comparison in experience is a room with old vinyl coated flooring that we wanted large ceramic tiles laid over many years ago. We were told that because the vinyl may be loose in some spots it had to be removed (at great expense), but an experienced older tiler said it seemed firm and the large ceramic tile surface would hold down any loose sections anyway. We took what we saw as a low-risk gamble & went with him. There has been no sign of problems in the 10 years so far.

[MitchellMc]

Perhaps I should have clarified further @3ltiffo. Whether you are paving with a bed of mortar or tiling with an adhesive, you are still sticking something to a substrate of Pebblecrete. Due to the issues explained in the document above, it is not advised to adhere anything onto Pebblecrete. The Pebblecrete needs to be removed. If an adhesive won't stick, a cement-based mortar won't either.

If you Google "Can you pave over Pebblecrete", you'll find limited to no results as it isn't really something that is done. I suppose laying a bed of mortar and creating a new substrate would be better than trying a glue that might de-bond, but you're really pushing new territory. The mortar won't stick to the Pebblecrete, but if you lay a thick enough bed, it potentially won't go anywhere.

Perhaps if you speak with a few paving companies, you'll then be able to gauge from their responses what the chances are of paving over Pebblecrete working. However, I suspect you won't find anyone that is willing to warrant a job over Pebblecrete. They'll want to remove it.

Mitchell

[Stuckster]

Might be a bit late to this discussion, but for future reference this article may also be useful.

https://luxapool.com.au/luxapool-epoxy-pool-coating-pebblecrete-surface-pools/

If they can get pool paint to stick to pebblecrete underwater then it should be possible to stick pavers over it.

I also had a look at the document @MitchellMc referred to.

Seems like the first step is to determine whether or not your pebbecrete actually has a resin based epoxy sealer on the top surface. If the binder is Portland cement based instead then you should be fine.

If it has a resin based epoxy sealer then an Muriatic acid wash (as explained in Luxapool's article) could be a good preparation step to remove the epoxy resin and etch the surface to enable an adhesive to bind to the aggregate. A wire brush could also be used on any tough spots.

Either way, if the original pebblecrete is well-etched, clean and dry then a suitable adhesive or mortar mix should bond strongly to the surface. 

PS: Before anything, I would strongly suggest repairing any "drummy" sections of pebblecrete that have delaminated from the base (as per the article) to avoid future issues with movement or lifting of the new pavers.