[Greenbuilding] Fence posts--gravel or concrete

JOHN SALMEN terrain at shaw.ca
Mon May 9 16:18:14 PDT 2011


Just to confuse everybody (and save a little gravel, concrete and wood).
Here is a footing I use on delicate sites that is immune to frost heave.

I pound in 3 pieces of rebar in a tripod pattern (can get a pneumatic
pounder for this (electrical ground pounder).  The pieces extend out of the
ground about 12" and overlap.  Lay 4-6" of loose gravel on the ground and
build a small box form surrounding the rebar (8x8x8 -12x12x12 whatever is
needed - can be tapered to post dimensions). Insert and level a  flat steel
or L steel bar (can be decorative) that sticks up high enough to support
whatever post size you are using - with holes drilled for bolting on a post.
Pour concrete - bolt post to steel.  

 

John

 

From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Rob
Dickinson
Sent: May-09-11 2:25 PM
To: Green Building
Subject: Re: [Greenbuilding] Fence posts--gravel or concrete

 

Hi Ben,

 

Good question. 

 

I'll have to look for the book I was reading that had a recommendation on
this, but I recall it being a combination of the two.

 

I think the idea is to have the very bottom of the post be in a layer of
gravel so that any water that gets to the bottom of the post can drain away,
and then to have concrete above the gravel layer to hold the post in
securely.

 

If you have the post bottom in concrete, water will flow down the sides of
the post and pool in the base of the concrete cup that you have created and
accelerate the rotting of your post.  Even if it is treated wood, it reduces
the lifespan if the base sits in water long-term.   The gravel at the base
solves this.

 

Or at least that is how I remember it.

 

Rob

 

 

On Mon, May 9, 2011 at 2:01 PM, Benjamin Pratt <benjamin.g.pratt at gmail.com>
wrote:

I promised to help my friend put in a fence this summer. I was
recommending that he use gravel, or class 5 crushed gravel, to set
them in, rather than concrete. From my experience, concrete breaks
apart anyway when the post swells. I also think the posts would rot
more slowly in gravel, especially if there is a lot of gravel in the
hole underneath the posts. But he is skeptical. Do you agree with me?
Also, how deep should he put them in?  This is in minneapolis, MN.

-Ben

PS. No , he will not consider using a GFX  ;-)

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