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How to attach a post to a concrete retaining wall?

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How to attach a post to a concrete retaining wall?

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I'm attaching a timber post 100 x 75 mm about 1600 high to existing fence post and retaining wall. The purpose is to hang a side gate to it. Due to existing landscaping and drainage I'm not digging it in.

I note there was a similar question in May/June which has confirmed that using right angle brackets is the way to go. The difference is that  I cannot access the back of the sleeper. I have purchased dyna bolts to attach the brackets.

I note it was suggested to use Ramset 300ml Chemset UltraFix Plus. What does this do? 

Any tips on how to go about this would be helpful


Retired Team Member
Retired Team Member

Re: How to attach a post to a concrete retaining wall?

Hi @Amanda7,


Welcome to the Bunnings Workshop community! It is awesome you have decided to join and jump straight in with a great fencing question. Our resident DIY expert @MitchellMc will be back online Friday, but in the meantime let me tag our wonderful Workshop members @TedBear and @Adam_W to see if they have any suggestions. 


Feel free to post about any home improvement and garden questions you may have, we are happy to help. 




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Bunnings Team Member
Bunnings Team Member

Re: How to attach a post to a concrete retaining wall?

Hi @Amanda7,


Ramset 300ml Chemset UltraFix Plus is an adhesive designed for glueing threaded studs or reo bar into concrete. It can also be used as an additional measure to ensure Dynabolts lock into porous substrates.


Are you aligning the new post with the timber post? If so, I'd recommend coach screws for fixing the two posts together; you might also like to run some construction adhesive between them before joining. 


If you plan on having a Dynabolt go through the steel and into the concrete, you'll need to pre-drill the steel post. Those steel posts can be tough, so I'd suggest using a cobalt drill bit. Be careful to stop as soon as you get through the steel and switch to a masonry bit for the concrete section.


If you can illustrate on your image exactly where you'll be placing your new post, our helpful members might have some other valuable suggestions.


Please let me know if you have any questions.




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Re: How to attach a post to a concrete retaining wall?

Hi @Amanda7  @MitchellMc @KatieC 


Firstly I would not  swing the gate of the fence if at all possible, as one day that fence will need to be replaced so its easier to put the latch on the fence side. You all are going to hear that often as I learnt that lession the  hard way


But no doubt you have very  good reasons  I cant see in photos for mounting on the fence,


For now  lets  assuming post is alinged with the steel and the timber fence  upright.  First thing  Throw away post. 


Why not directly hinge off the the existing fence steel and timber?  Screwing hinges to a metal frame is easier (simple metal screws) and stronger no need  for glues (which will fail in time re gate impacts). no need for brackets no need for post. Also simple coach bolts  predrilled into fence for the upper hinge.


Use  your timber post on the  house wall side bolt it to wall I like  using long coach bolts into rawl plugs you only need top middle and bottom.   Add your latch here,





Re: How to attach a post to a concrete retaining wall?

I have to agree with @Jewelleryrescue with this scenario.

Never hang anything off of a retaining wall where there is a side load in excess of what the wall was designed for (often by a Structural Engineer).

If that wall fails, the first question is going to be asked as to why this occurred.

Yes it is probably only a gate, but you need to err on the side of safety, having a retaining wall of any size collapse because of a modification that the Engineer never planned, puts people in a situation of some liability especially if it damages a bordering property.



Mike T.


Kind of a Big Deal

Re: How to attach a post to a concrete retaining wall?

Good Morning ! @Amanda7 


"existing fence post"


It's a lovely Saturday morning where I am and I'm looking closely at that post in your photos.

I'm rather ignorant about retaining wall steel and their associated hardware but that post appears to be just sitting on the metal and concrete sleepers?

Then there looks to be some sort of bracket inserted between the steel and concrete and resting against the wood post - nothing is attaching it to the wood?

How is that bracket attached to the steel?

Spot welded maybe?

To me - it looks like if I pushed that post it and the fence, would wobble back and forth?





Re: How to attach a post to a concrete retaining wall?

Hi  @Noyade 


If you zoom in on another photo  I can see two screws into post timber in that metal upright bit but you have to look had  I looked  because  you got me curious


I can only assume there is metal screws lower down holding the metal plate in place. unless it is friction fitted with the concrete sleepers locking it into place which wouldnt surprise me.

Re: How to attach a post to a concrete retaining wall?

Thanks @Jewelleryrescue -  my Zoom powers are poor.

But normally there would be a bolt through the top hole and once the post is aligned vertically, another bolt is placed through the slot - so shaped it allows adjustment?


Anyway - @Amanda7 - I present the "Ponderosa" ranch style gate opening with a high beam connected to the house. Critical is a pre-drilled steel plate welded as shown. I 'believe' this will not only allow you to swing a gate from this side but also strengthen the fence without compromising the retaining wall.

Was gonna draw more, but the mosquitos were really bad outside.



Re: How to attach a post to a concrete retaining wall?

Hi @Noyade   


I   nice free hand drawings again :smile: 


But most of  all I like the over head timber that alone will stop fence  leaning. 


We know  under ground is off limits but I would add new post free of the fence some how. 


Getting Established

Re: How to attach a post to a concrete retaining wall?

The bracket for the post is part if the retaining bracket - one piece with the post bolted to it. Quite sturdy

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