Latest Discussions : Lawn & Garden

bobothewrench

10:05AM | 04/21/04
Member Since: 02/12/04
12 lifetime posts
I have seen the DIY shows on TV advocating the use of gravel to sink treated wood fence posts for years, yet the majority of contractors who do this work still use concrete.

I am building a 6' tall pressure treated wood fence. The holes will be 9" diameter, 42" deep (I live in Alberta, Canada) drilled by a tractor, and the posts will be 4x4x10' pressure treated. The contractor doing the drilling is also bidding to sink the posts in 2 bags concrete/hole.

I am considering sinking the posts myself by just filling around the post with gravel up to the top. I will save myself a lot of cost, effort, and the TV shows say the fence lasts longer because water is not held in contact to the wood.

I would appreciate any opinions on this. Will the fence be soft? Will the gravel withstand frost heaves? Thanks.

tomh

10:25PM | 04/21/04
Member Since: 07/01/03
549 lifetime posts
The main problem with gravel backfill is adequate compaction. Concrete is a semi liquid and tightly adheres to the hole and post making a stable post that doesn't move. I have never been able to get that long term result from gravel. I used gravel backfill on a horse fence and would never do it again. The replacement fence was done with concrete backfill. Especially around gates and anyplace subject to lateral stress, concrete works better. Gravel might be fine for a garden or decorative fence, but if people sit on it, or it contains livestock, go with cement.

treebeard

07:11AM | 04/22/04
Member Since: 01/14/03
264 lifetime posts
My personal and professional experience has always been to use gravel and not concrete in these situations. Gravel can, indeed, be compacted sufficiently to hold fence posts in place. And the gravel will allow water in the ground to drain away, where as concrete will hold the water around the post longer. And that's not a good thing. Set wood 'on' concrete, not 'in' it.

bobothewrench

09:47AM | 04/22/04
Member Since: 02/12/04
12 lifetime posts
Thanks for the info!

I have a related question. I am trying to build a fence that is somewhat distinctive for not a lot more money than a standard squarish privacy fence.

One design that I am considering is to use 6x6 posts 8 ft on center, 3 2x4 stringers between them, and the fence slats all cut to a point on top...essentially a 6 ft tall picket privacy fence.

Do the mitre cuts at the top of a picket do an adequate job of preventing water from seeping into the end grain and discoloring the slats, or is this design bad and a top cap piece mandatory? Thanks.

treebeard

02:52AM | 04/23/04
Member Since: 01/14/03
264 lifetime posts
If it's pointy pickets you want, then you should stay with your design. Pickets have been around for...welll...a very long time. And the end grain has always been exposed. It used to be that all pickets fences were painted, and painted with lead paints we can't use anymore. The end grains were pretty much sealed by the paint, so water didn't get in until fence maintenance came to a stop. Same thing today. End grains are the same, paint isn't, and many times maintenance isn't. And it won't matter if it's a pointy picket, or flat across the top. The end grain, if not sealed, will suck up the water like a sponge.

BV013199

08:19PM | 10/22/16
My personal and professional know-how has always been to use gravel and not concrete in these situations. Gravel can, indeed, be compacted sufficiently to hold fence posts in place. And the gravel will allow water in the soil to drain away, where as cement will regard the area around the post longer. And that's not a good thing. Set wood' on' concrete , not' in' it.

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