Can you build a deck or patio over a broken/uneven concrete slab?

[Manufuzz]

Hi,

We have a concrete slab (around 3 x 3m) that is broken and not even (see images). We don't want to get rid of it because it would cost a fortune so we would like to build something over it, but we're not sure what's feasible given that the slab is broken.

What options do we have? Could we build a deck over it (right on top or higher) or could we cover the whole slab with soil and then make a patio with pebbles? Or would we need to resurface the slab to make it even and then build over it?

We're not sure what to do. Any suggestions would be appreciated. Thank you!

Manu

[EricL]

Hello @Manufuzz

Welcome to the Bunnings Workshop community. It's great to have you join us, and thank you for sharing your question about building a deck or patio over a broken concrete slab.

I believe that the slab has cracked due to age and movement underground. Due to this event, I suspect that there is a possibility that the slab has settled into its natural footing. If the slab has not moved in the last five to seven years, odds are it will not be shifting anytime soon. 

If you are building a low-level deck I suggest using Builders Edge 70 - 170mm Bigfoot Xl Pedestal Feet. It's height adjustable so if the slab moves you can adjust the level of your deck. If however, you are building a taller deck use TuffBlock 300 x 300 x 90mm Instant Foundation System Deck Support. There will be no need for you to break the concrete as TuffBlock can be placed right on top of the concrete.

Building a garden over it is definitely a fantastic idea. However, you'll need to place timber sleeper borders around the slab in order to prevent the soil from being washed away.  

If the concrete slab moves you can change the timber footing of the deck again, without having to break the concrete.

Let me call on our experienced members @Adam_W, @diy_hausdesigns and @Backyardtradie for their recommendations. 

If you need further assistance, please let us know.

Eric

[Manufuzz]

Hi Eric,

Thank you so much for your help!

It's hard to know whether the concrete slab has moved in the last years as we've only just moved in this year. But most likely, it's been like that for a while. Good to know that there are height-adjustable supports. 

If we were to go with the soil idea, would any type of soil do the trick? 

Manu

[EricL]

Hi @Manufuzz

If you are planning on planting vegetables you'll have to use a taller garden bed. I suggest having a look at our Top 10 most popular raised garden beds. You can build the garden bed around the concrete slab so that you can effectively cover the damage on the slab.

As for the soil, I suggest getting the best garden soil you can get. In this manner, any vegetable you plant will have lots of nutrients to use.

If you need further assistance, please let us know.

Eric

[Manufuzz]

Thank you for your help!