Postmix for posts

[Jupiter01]

Hi,

I am starting my feather edge fencing project this Saturday and wanted advice on how much postmix I should use for each post. The posts are 6ft tall and 120x100. I intend to put them 600mm into the ground.

Also, is it necessary to put pea shingle at the base of the post?

 

[London Mike 49]

This may help ; http://www.pavingexpert.com/featur02.htm

 

[Jupiter01]

thanks for the link. Very helpful. It doesn't tell me about how much postmix I should use. I would appreciate any advice on this

 

[Doggit]

Although you're digging the holes 600mm deep, the amount of postmix required will depend on how big you make them. Assuming the hole isn't too wide, you may get 3 holes out of 2 bags, or it could well be as bad as 1 bag per post.

 

[Nige F]

No need for pea shingle - they will rot eventually just at the ground level - unless they are oak . I always do 1 bag per post

 

[Doggit]

Well done Nige, forgot to mention that the problem with Postmix is that it'll settle level and water collects at the base and rots the post. Leave about inch below the ground level, and then use a cement and sharp sand mix to give a rise towards the post.

 

[Jupiter01]

so, I dug holes 600mm deep ans followed the instructions in postcrete to fill water up to 1/3 mark and then pour postcrete. I reckon it all finished at around 300mm. Is that sufficient and so I pour earth back over the remaining 300mm?

 

[Doggit]

The last time I used postcrete, I filled the hole with water, and then added the postcrete, but having checked the factsheets, you've done it correctly. But if you fill it with earth, unless you bitumen the post, the earth will just rot it. I wonder if the instructions were for concrete posts rather than wooden ones - which I assume you've got.

 

[Jupiter01]

yes, I have wooden posts. I assume I have to pour in earth as at the moment only 300mm is set in concrete and 300mm is empty.

initially I thought that 300mm of concrete may have been on the low side by that around 1.6 bags on each hole.

 

[Doggit]

Which option will you go for, Bitmen the post, and then fill with earth and tamp down bloody hard; knock up some concrete and fill the hole to the top with a gradient above the level of the earth, or more postcrete, and then feather upwards toward the post with a concrete mix.

 

[Jupiter01]

I topped up the concrete slightly so I would say that around 400mm of the 600mm is covered by the concrete. I also sloped the concrete so that water doesn't collect at the base of the post. I will pour earth into the remaining hole and tap it down. I did call the supplier and this is what they recommended too.

A further question please: my slats are 4.5 ft in height I then have a gravel board underneath which takes the total height to 5 ft. Where should I be placing the arris rails? I have a set of two running behind the boards, to which they will be nailed but I'm unsure on where exactly I should position these. I don't have the cut out on the posts and will be using brackets.

 

[Doggit]

Hang on Jup, am I right in thinking there'll still be 200mm of earth around the base of the post. Even with treated posts, the earth will still rot them. Try a foot from the top and bottom for the Arris rails.

 

[Jupiter01]

There are tonnes of videos on YouTube where they pat on earth over the cement and also the postcrete instructions are to fill the whole 1 third and the pour postcrete. Is this not sufficient?