# Forum Home Renovation Concreting  Subsiding concrete block

## Wigspotter

Hi, just after some general advice.  
The stairs from my back deck land on a large concrete block (poured in situ about 2y ago, about 1m x 1.2m x 0.8m tall). It has subsided on one side (opposite to where the stairs land) by about 4-5cm.  
Im thinking to dig under and jack it up and then support underneath with concrete. I have a 3.5t hydraulic jack from my 4wd. That should be enough, shouldnt it?  
Any tips for supporting underneath? Feed as much concrete underneath as I can + some reo bar?  
Any and all advice welcome.  
Thanks, Conor

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## Tools

That's a hell of a footing to support what I assume is a timber stair? 
Tools

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## Marc

your landing is close to a cubic meter of concrete and weights in at 2.4 ton if it is all solid concrete. Probably the reason for the subsidence. Soil was likely not prepared for such weight. 
Can you rise it? Sure. The question is will it hold without breaking. I say it will.  
As for how to prevent it from going down again, that is another story. Ideally you should stomp the underlying ground hard with aggregate, pebbles, blue metal or similar, but easier said than done. You will need to be creative. Increasing the "footprint" would be ideal with say a row of bricks half under and half out. Pouring concrete under there, will prove to be a challenge.  
You will need to play it by ear, starting to see if it even comes up with a 4wd jack and what condition the underside is.
Best of luck and don't forget to post pictures  :Smilie:

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## Wigspotter

Thanks. Thats helpful. Its core is a bunch of old concrete pavers as filler so its basically solid concrete. Appreciate the weight estimate.  
Will have to work out how to post photos. To clarify, its sort of a landing which has a timber deck built around it. Theres a sandstone waterfall step down to the timber deck that wraps around the block. The deck was attached to the block and was being pulled down. Ive pulled the sandstone back, separated the deck and will give it new posts there. Just what to do about the block itself... 
Ill have a go with the jack and see what happens.  
Cheers, C

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## Marc

In case you don't mind spending some money there are companies that do this with resin injection

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## phild01

> Will have to work out how to post photos.

  https://www.renovateforum.com/f227/h...photos-120536/

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## Wigspotter

> https://www.renovateforum.com/f227/h...photos-120536/

  Ahh, need to use the full site, not the mobile site. Was wondering why it wasnt obvious. Will put up photos tomorrow.

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