concrete fence posts not the right length, so what to do

[happyhero]

Hi I am putting up a fence for the first time and my wife has finally chosen the panels which are a fairly common 180cmx180cm. I will fit a weatherboard at the bottom which is a fairly standard 15cm and I have always been told to put 60cm of post in the ground, well that all totals up to 255cm. It seems a fairly common layout to do yet the posts are sold at 2.4m and 2.7m with the 2.7m costing a fair bit more especially when you buy in quantity.

I had a load of vouchers for B&Q which I wanted to use to get the posts, but their posts are even worse at 2.36m which would only give me 46cm in the ground, is this enough. I'd like to get them here as not only are they cheaper, I can use my vouchers but I don't want to do a bodge job, what do you think. If I dig a decent hole and fill with cement will 46cm do it or is 60cm a minimum.

Any help or advice appreciated.

 

[nstreet]

I have always put a third of the post in the ground rather than a fixed 60cm. I have only installed wooden posts though, not sure about concrete

 

[Thermo]

doesnt matter what they are same rule applies. its not what the posts are made of its the wind loading on them, that acts as leverage to loosen them or pull them out of the ground. A few quid saved now, is not worth the hassle later on. Go to a proper fencing supplier, they will be cheaper than q and b anyway

then again its people putting them in at the wrong depth that helps to pay my mortgage!

 

[JamesA]

The weatherboard doesn't necessarily have to sit level with the surface, it just needs to be exposed by a few cm to stop the wood sitting in the wet soil.
Therefore I'm not sure that it has to be as much as 255. I was basically told the standard for 6 foot panels is 8 foot.
You're only allowed to have a fence 6 foot by law anyway, so you don't want to go too much over.
I used 6 inch concrete gravel boards and dug them in to the ground. This adds to the general strength of the slotted concrete posts.
You could have them showing just 2 inches above the ground.

 

[JohnD]

I use a 12" concrete gravelboard and a 5' panel with a 8' post. I let the gravel board into the ground a bit. I think it adds stability to the post in windy weather. they are rather heavy if you are working on your own.

I am toying with the idea of using a more solid piece of timber at the top and just slotting it into the posts. my top rails seem to "wear out" before the panel, either weather or cats claws.