Substituting concrete for wooden fence posts

20 Dec 2007
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United Kingdom
I have a wooden fence, 6ft panels with 75mm wooden posts, that has partially blown over in the recent weather. Much of the rest of the fence is in good condition, either more recently replaced, or in better drained soil.

I'd like to use slotted concrete posts to replace the rotted wooden ones, but I note that they slightly narrower across the slot (50mm) than the wood I am replacing (75mm). I was hoping that I could simply replace them and then as other parts of the fence failed in time, replace those with concrete too, until I had a completely concrete post fence with easy to replace wooden panels. But that will only work if the spacing for concrete posts is the same as the spacing for the existing wooden posts. So the question is, does the spacing need to change, or is the 25mm difference simply for clearance to allow the panels to fit easily and I am okay to just put the posts in the existing holes?
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I think part of the problem is also that the old pannels were in inches and the new are made in mm.
You can add 25mm batten to one end of the fence panels or 12mm each side. You wont see the battern because it will be within the slot. But once the concrete posts are in you will forever have to do this for any replacement panels. Yes the concrete posts allow for sliding in or out but the gap is very small and usually the panel is not slid in but is added with the post then in future some slide out better than others.
You will first have to dig out any existing concrete that the wooden posts are in, you may then end up with a massive hole that will need a lot of new cement to fix the concrete posts in as they can be a right pain to get out.
Sometimes people get around this by leaving the old concrete in and starting the new posts in a different position but over the years along my line of fence before we moved in when digging holes for plants along the border I kept finding old concrete post holes eventually I have now removed them all.
Depending on how many and the starting one you can put the concrete post in where they need to be to fit the pannels and make up the difference with a couple of fence boards at the start of the run.
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Thank you. That is very helpful.
It sounds like my plan is a non-starter and I should either replace the whole lot on the new concrete spacing, or continue to use 75mm wooden posts.
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Got to be concrete for me and concrete barge boards are a must too. Keep your old fence panels that are good but replace all the posts with concrete and fit the concrete at the correct spacing for new panels and then make your old panels fit that space.
I do not perticually like the wavy edge panels as I think the vertical feather edge look better and last longer and I find it best not to paint them just let them naturally "silver" but paint the top cap ridge every year. So depending on what you have might influence if you replace the lot.
I went through the same thing for years because some were good but it just meant that the fence was in a perpetual state of repair / disrepair and looked a mess.
In the end I bit the bullet and got a good fence company in to replace the whole lot in one go, considering having to have everything delivered and also taking old concrete and posts and panels to the tip in numerous trips ( risking a puncture at the tip ) and the whole week it would take me to do I deemed in not worth me doing DIY.

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