Urgent Advice on post hole fixing

BobAlger · Posted: Wed Jun 21, 2006 6:59 am Post Subject: Urgent Advice on post hole fixing

Please can someone advise on the correct hole sizes and amount of postcrete to be used for fixing 8' concrete fence posts as I am somewhat confused. Work starts tomorrow (22nd June) so an early response would be appreciated.

My current plan is to use a petrol driven auger to drill 8" round holes to a depth of 21" and to fix the posts using Postcrete. The DIY shop said use one bag per hole but another website indicates that this will only take about 1/2 bag for each hole of these dimensions and my concern is whether this is sufficient. What I don\\\'t really understand is whether its the hole that is supporting the post and the Postcrete is simply filling the gap or vice versa.

Many thanks

Bob Alger

JohnD · Posted: Wed Jun 21, 2006 7:24 am Post Subject:

The ground provides the support and the concrete stops the post from rattling about. It also provides a wider bearing to spread the forces from the post over a wider expanse of ground.

A deep hole is better than a wide one. Your hole borer should be good for that. Any soil that is loosened by diging needs to be excavated and replaced by concrete, since loose soil is not supportive.

If the hole is too wide you can economise on concrete by packing large stones or pieces of brick in, making sure each is well encased in concrete so you have a monolithic mass.

The top few inches of the hole do not provide much support, but it is useful to bench up the top of the concrete towards the post to help rain run away from it (not important of it is a concrete post) and so that you do not have a great wide patch of concrete showing through the ground.

BobAlger · Posted: Wed Jun 21, 2006 3:12 pm Post Subject: Thanks JohnD

Thanks JohnD for you prompt reply which has put my mind at rest.

All I need now is this wind to die down before tomorrow!!

Thanks again.

Bob Alger

JohnD · Posted: Wed Jun 21, 2006 3:16 pm Post Subject:

p.s. if you're using concrete gravel boards (I think they're great) sink your posts so that the boards will be a couple of inches into the soil. You can easily scrape out a groove in the ground for it and brush back after.

Thermo · Posted: Wed Jun 21, 2006 4:03 pm Post Subject:

i always use some hardcore at the bottom of the hole to pack out the post so that it is stable and level before the concrete goes in. It stops it moving during the post mix going in and it gives a much firmer post

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