Patio concrete slabs dropped

[perda]

Hi,

2 part concrete question:

part 1. my back patio concrete slabs have fallen quite a bit due to groundwater getting underneath. Have solved the water issue (hopefully) . Wanting to do decking over the top of the concrete slabs. Is it best to try and resurface the area with a concrete resurface or could you just put decking over it as is. Photo attached as reference . 

part 2. I have in the same area some concrete slabs for a walkway that have fallen toward the house/brick patio.. again, could I use a resurfaced to get the fall away from the house, or is it easier to do something else? Photo attached as reference 

** budget is an issue as cannot afford to remove and relay concrete **

 

[EricL]

Hello @perda,

Thank you for sharing your question about your patio concrete slabs. 

Yes, you can build your deck over the slab. It is vital that your water drainage be 100 percent effective. Any movement or sinking of the slab will affect the deck and move the footing of the frame located in that area. Resurfacing the slab will give you a flat surface to build from and will make the assembly of your deck much easier. 

Resurfacing the slabs that have fallen towards your house would be a good solution. It is affordable with a quick turnaround time and does not involve a complicated process. Once resurfaced make sure that the water drainage for this area is secure as well.

I've also included a list of our Top 10 most popular deck projects for your reference.

Let me tag our experienced member @TedBear as he might have come across this type of situation.

If you need more information or advice please let us know.

Eric

[TedBear]

Hi @perda, I can only back up @EricL 's  good advice.

I am always cautious of sinking surfaces, however if you support your decking on stirrups, then setting them in concrete footings should let you know if the soil is dry and stable.  Surfaces sink for a variety of reasons, including the original installer not compacting the soil, and/or someone building nearby doing compacting that resettles your soil... and you have found a water issue too.

I am wondering if resurfacing may be a wasted effort if the concrete is to be covered by decking and is perhaps still a little unsupported??

You will, of course, need an air gap between the decking supports and the concrete surfaces to prevent wet - rot.

Best wishes for the project... I hope we all get to see the end result.

[perda]

Thanks Eric and TedBear!!!. Ill look to first resurface/regrade the small steps. I think for the patio, more time is needed to assess the significant drop in the patio slabs..winter and plenty of rain is probably not the best time to do this activity.

Any recommendation on product that is good for re-grading/surfacing concrete would be greatly appreciated.

Cheers

[Jason]

Hi @perda,

@EricL will be happy to recommend products when he is back on the site on Friday. Apologies for the delay in the meantime. 

Let me tag @Adam_W to see if he might be able to share his thoughts. 

Jason

[EricL]

Hello @perda

I totally agree with you on the timing of this project. I would wait until winter has gone past and summer has come into full swing. I suggest using the Bastion 20kg Concrete Mix. It's a concrete mix that is a blend of sand, cement, and stone, perfect for all the needs around the house.

Here are two very handy step-by-step guides that I think will be useful:

• How to mix concrete

• How to level concrete

​​​​​​​ Just a friendly reminder to make sure to please read the instructions at the back of the bag before you begin your cement works. 

Please keep us updated. I look forward to seeing the patio slab repaired and resurfaced.

Eric

[perda]

Thanks Eric, greatly appreciated... will update once done to this thread