Setting posts in cement vs concrete

[schwartzy]

We have jus had a fence errected and the posts seem to be set in cement rather than concrete (i.e. cement/gravel/sand). Should I be concerned over the longevity of the fence? Is this a comon practice?

Michael

[Burnsy]

Fairly common practice for fencers over here to use the clean sand they dig out of a hole to make up a mortor mix with, especially on multiple sites where they are putting up big metres of fencing for the same builders or developer. These guys are generally cheaper and that is why they get the contract. Good fencers use roadbase to mix up concrete.

[silentC]

They've probably used rapid set concrete, which does have sand and aggregate pre-mixed in the bag. I've seen fencers pour water in the hole then empty half a bag of rapid set into the hole and that's it. I can't imagine anyone thinking straight builder's cement would be satisfactory.

[Ivan in Oz]

I'd say it's a Weak Mortar Mix.
The cheaper the Contractor, the Weaker the mix.

What was the agreement
or do you have it in writing

Perhaps;
what you said is not what they heard
nor wanted to hear

[quercus]

Mixing cement with the dirt from the hole is an age old practice for paling fences, with good results. Cement stabilised rammed earth is the actual term. As long as they have put enough in - a third of a 40 kg bag used to the rule of thumb. T
his actually can prolong the life of the post. I have seen plenty of posts that were concreted in which have rotted away. THis is due to the water pooling at the top of the post, as the concrete stops the water draining away. Cement stabilised soil dries out better. I put in fences for years, and you saw it a lot. THe interface between the wet soil and the air is where it rots.

Often you would be amazed by how bases of the redgum posts were in perfect condition after you pulled them out after god knows how many years, they just had rotted through where they met the ground though.

[dazzler]

If theres a bodgy way of doing something someone will find it. With rapid set available everywhere god knows why you wouldnt use it

[silentC]

Mixing cement with the dirt from the hole is an age old practice for paling fences ...

Good point. I was thinking of a colorbond fence with steel posts rather than timber.

[malb]

Will be replacing an old (25+) paling fence with colourbond later this year. Posts were erected using cement/clay from hole and rammed. Six units were built next door 8 years ago, with dunny, concrete blocks etc all dumped off truck against the fence for use by the developer.

Our side was excavated 2 years ago for a mother of a retaining wall, up to our edge of the posts. Developer next door had broken off 6 posts when dumping his materials along the fence, but all remining posts and the stumps of the 6 broken ones were still 95% intact and set in the rammed mix. We did have some panels collapse into the cut in a storm, but this was always panels connected to a post broken off at ground level, and the collapse was checked at the first intact post.

Based on this, I believe that it is an adequate method of supporting posts in postholes provided that the surrounding ground is fairly hard and rigid.

[schwartzy]

I was first tipped off when I saw bags of cement but not agregate or sand. I will have to look over my quote. My side fence is up but he is about to commence on the back fence. He just seems to pour cement into the holes. And everywhere else. Not sure if he uses water. I spent what seems like forever collecting crusty cement from the surrounfing garden.

Michael

[silentC]

Just check the bags because I still think it could have been rapid set concrete, despite all the above. There are three products you can buy that come in the same sized bags: raw cement, pre-mixed concrete and rapid set. The last two have sand and aggregate pre-mixed in the bag.

[Dirty Doogie]

There is another "trick" the contractor could be using here. Hole is dug and a little pile of cement put in the bottom of the hole, post gets seated on it, hole partially back filled and tamped - then about a 1/3 from the top of the hole a collar of pure cement dust about 50mm deep is poured around the post - then backfilled.

The theory being that the cement collar will harden and stabilize the post against lateral movement while at the same time delay rotting of the post.

[schwartzy]

Definitely Cement. The packaging shows various recipes for different concrete, render etc. mixes. I still have a bag sitting at my place.

<o></o>The fence contactor is a Jim's Fencing franchisee. Should I contact Jims re standard practises?

<o></o>Michael<o></o>

[echnidna]

Cement/soil mixture is the normal fence building practice in Vic.
It was developed by the CSIRO yonks ago to eliminate soleplates and struts on fences.
It works well.
Only use concrete for gate posts