How to pave over uneven concrete slab?

[GardenHelp1]

Hi!

Grateful for any tips or advice I have a raised 3m x 3m concrete slab in my garden which used to have a large water tank on it. I've demolished the tank and would like to pave over the slab (ugly discoloured concrete) so I can use the space for some garden troughs etc. I'm totally stumped about how to do this though - the slab dips in the middle (around 15mm) and water pools in it. 

I would like to put limestone pavers on it but what would be best - self level the slab then sand / cement then pavers? I'm worried if I don't self level the slab then water will just pool and will wash out the sand between the pavers? I have a small water tank to put on top but it's a bit leaky and will discolour any light pavers so I might have a 'cut out' area where it just sits on gravel - does this sound ok?

Thanks!

[Dave-1]

Afternoon @GardenHelp1 

I like the sound of the area being reused Any chance of a photo or two of the area and general area?

Paving with sand underneath is probarlly the way I would go, Id make sure the edge has a fixed edge to keep the pavers in line and it would also keep the sand in place. 

In regard to the 15mm extra depth, I dont think I would worry to much especially with the sand leveling the area first. 

With an edge I am talking about fixing something like timber sleepers to the slab either on the side so they extend up or on the top flat down to give the whole area a captured spot. for the sand and pavers to sit within.

Dave

[GardenHelp1]

Hi Dave,

Thanks for your reply 😁 Here's a photo - excuse the chaos 😶 I like the idea of not having to self level - this was the part I was going to get a tradie in to do. My concern was that the sand would get waterlogged but it sounds like that might not be a problem. The sleepers are a good tip - any hints on how to attach these to the slab without having to drill into it (some kind of adhesive maybe?)

I'm guessing I'm looking at 30-40mm of some kind of bedding sand, then the slabs, then the sand to fill the gaps? 

Thanks again! 

[Dave-1 · Accepted solution]

Howdy @GardenHelp1 

Thank you for the photo That will look great when you are done.

Fixing the sleepers/edge to the concrete I would strongly suggest to use something along these lines Ramset 7.5 x 100mm Galvanised Masonry Anchor Screw - 50 Box Not necasarily 50 but the type of screws. If you are unsure of how to drill concrete or dont have a hammer drill let us know as it can be daunting. I know I was the first few times using a hammer drill.

The Screws I have used multiple times and seriously they are about the easiest screw I can think of to use. The only thing to make sure of is the whole you drill needs to be deeper then the screw that will be in the concrete and it needs to be empty of dust (yeah I have tried it without cleaning the dust out and it didnt end well lol) The sleepers would only need 3 or 4 screws to hold them in place. I feel any glue will have a much shorter lifespan and then shift and then you will have to repair down the track.

I am unsure on how good/solid the slab will be but it should be having had a water tank on it before for years and there dosnt seem to be a crack in it. 

So the sleepers would be attached directly onto the concrete slab (Drill the treated timber sleeper first with a timber drill, then lay the sleeper on the concrete and mark the holes required. Then drill with the masonary drill bit that suits your screw size), the sand is on the inside of this framework to bed the pavers in. It dosnt have to be to thick just enough to be level across the surfface. 

Thinking about your question about attaching the sleepers. If the edging is heavy enough you could see how it works (Still think it may move over time) you could use Bessa blocks or something large and heavy along the edges and then fill the center with the sand and pavers. Pioneer 200 x 75mm 1.58m Ironbark Reinforced Concrete Sleeper  is a possible choice but remember becaus eits not fastened they could shift and then you will have uneven pavers show up.

Dave

[GardenHelp1]

This is great, thanks Dave!!

[EricL]

Hello @GardenHelp1 

Welcome to the Bunnings Workshop community. It's fabulous to have you join us and thanks for sharing your question about paving your concrete slab.

It's wonderful that you've received fantastic advice from @Dave-1. His idea of using timber sleepers to contain the area is spot on. Just to add to the suggestions made, I recommend using Zenith 14G x 100mm Galvanised Type 17 Batten Bugle Head Timber Screws - 25 Pack to anchor the corners of the sleepers together. This should greatly reduce movement and keep your sleeper assembly secure. 
 

If you need further assistance, please let us know.

Eric