Ballast/cement or Postcrete

[kiteman69]

Evening all, I hope we all had a nice Bank holiday.

This question is aimed @ Thermo, as it was he who put the idea in my head.

If I am going to support my decking on approx 25 posts, each posts being encased in a 12"x12"x12" concreete block, with an additional 1-2" exposed on the top so that water would not collect around the posts and simpy run off the foundation How much "stuff" do I need?

I was going to order 25 bags of postcrete (and then buy extra as and when needed) or do I get a 1tonne bag of ballast and 6 bags of cement and make a 6:1 mix. Any unused ballast would then be scattered around underneath the decking.

If the latter, would I make the mix dry, in a wheelbarrow, and add this to the hole (tamping down as I go) or a wet mix (would you recommend hiring a mixer for this job).

Thanks in advance

 

[Burnerman]

Sorry its not Thermo, but if you don't mind me butting in?
I avoid postcrete.....you get about 1 minute to work it and then its off.
I'd hire a small Belle mixer, and use 4 parts aggregate, 4 parts sand, 1 part cement for a wet mix - and tamp the stuff down nicely, supporting the posts if needed until its gone off.
Enjoy!
John

 

[Thermo]

use ballast and knock it up in a barrow. You certainly wont need a tonne bag. Even if you had 25 of those holes with nothing in you will only need about 2/3rds of a bag, but you have cement to go in and the posts will be in the hole. Youll get about 2 post holes out of each bag of ballast. So allow about 15 bags and a couple of bags of dust. Ram it in dry and you can carry on working. at the end of the day when youre finished, ram it again and then add teh water. With postcrete it still doesnt go off fully, you then work on teh deck or the post and it loosens up.

Why do you want to spread ballast under the deck???

 

[kiteman69]

Why do you want to spread ballast under the deck???

Saves putting it in the skip.
Thanks also Burnerman, for your advice.

 

[WabbitPoo]

25 posts? Blimey, how big is your deck?

 

[kiteman69]

approx 44 m2