# Forum Home Renovation Concreting  Joining pier liners

## MattyGF

Hi guys, 
One of my upcoming projects is to extend the concrete footings of our deck support posts (150mm Diam CCA post) because the timber post near the top of the footing is rotting from wet soil contact.  
The plan is to chemset vertical N16 deformed reo bars into the top of the existing circular footing that surrounds the post and pour 32mpa concrete to extend the circular footing approx 600mm vertically. 
I will also dry out and epoxy coat the timber to hopefully preserve or prevent further decay, before concreting. 
To extend the footing I need to cut and sleeve pier liners around the top of the circular footings for formwork purposes. 
Just wondering if anyone has done something like this? 
I am thinking of pop riveting the cut formwork sleeve and perhaps concrete nailing the lower 50mm portion or so overlapped into the existing footing to keep it in place. 
Any thoughts or experience comments with this would be appreciated. 
Cheers
Matt

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## Marc

Feasible, but perhaps replacing the post would be a better alternative.
If you are determined to do this, first thing that comes to mind is that you don't need to keep the footings extension round. You can make a box for formwork around the existing footing, go deeper and then up as far as you please. 
The question remains, what size and how good are the existing concrete pads? Can they take you drilling 20mm holes for 16mm reo? 12mm is plenty. 
When you pour concrete around the post, you end up with a hollow concrete tube. Needs at least 100 mm around the post, and plenty of steel rings around it.  I would make a 400x400 box. 
As for the rotten post. you can try to stabilize it with low viscosity epoxy.
All feasible, but not cheap and lots of work. 
My neighbour patched up his jetty pylons by pouring concrete in a sleeve around the timber post. It is ugly as when still holding up, just.

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