Best method for fixing posts into concrete?

[Harrris303]

Hi all, I recently helped a friend build a timber cart-shed which was good fun and really interesting, using traditional techniques, and hand-tools where possible, draw-boring all joints etc. It all went smoothly and came together really well, except when it came to setting the posts.
My friend used short sections of scaffold pole, one end concreted into the ground, the other end pushed up inside the base of the post. As far as I know he'd done this before with no problems but this time the finished frame ended up with a bit of a wobble to it, nothing too serious but more than is ideal. Personally I thought there was too much scaffold pole showing between the concrete and the post, giving the scaffold too much space to flex and causing the wobble.

Anyway long story short I'm just wondering for future reference if there are any fixing methods which people favour over others for strength and sturdiness etc. I know you can buy fixings based on the same principle as my friends scaffolding idea, and also ones which just bolt the posts to concrete etc.

Basically I'm just hoping to start a little brainstorming session about the best ways to fix posts to the ground. Any suggestions are welcome. Thanks very much in advance.

 

[DragonImprovements]

Am i missing something here? Why not set the posts in the ground and not on the ground?

 

[John15]

The only method I have used is to surround the posts with approx. 300 - 400mm of concrete, can be a 1:5 mix or a little weaker. Bring the concrete about 25mm above ground level then form a weathering slope to shed water. You can be sure of getting the correct top level by this method

Another method is to form a concrete base to just above ground level, then bolt a shoe to the concrete to take the post.

There are probably a few more methods which members will come forward with.

John

 

[Harrris303]

I thought the main reason is so that the posts aren't just sitting in water for ages every time it rains. I may be wrong?

 

[Harrris303]

Thanks John that sounds pretty good. If that's what you've always done and never had any problems with. I've been looking at those metal sleeve things which you mention too and they seem pretty good, although I guess you rely on the frame being as sturdy as possible because they won't add any extra sturdiness to it.

 

[Aden30mm]

My take is to use a suitable timber (western red cedar). A third of the post should be in the ground, this normally means 2 foot in the ground. The base of the hole I always place some pea gravel to allow any water to drain away from the post end. A fencing pal, also advised me never concrete to surface level and just pack soil on top of the concrete, as its kinder to the posts to allow some movement.

With regard to metal post fixings, I think fencing contractors don't rate them. They must be a swine to remove and replace. I don't know how they would stand up to the wind loading, potentially allowing for post to shear at the metal/wood connection?

My last fence posts my farther and I installed lasted 18 years, but I have some professionally installed fencing that was installed in 1988, last year I had to repair two posts with a concrete repair spur, but many are still in fine fettle.

One last thought, I have just installed an eight panel fence adjacent to row of Leylandii trees on my neighbor land. Digging the post holes was very difficult due to the roots. However, the hole were very dry due to these trees, so at last I have found one use for these trees, they keep your posts feet dry!!!

 

[billybuntus]

My take is to use a suitable timber (western red cedar). A third of the post should be in the ground, this normally means 2 foot in the ground. The base of the hole I always place some pea gravel to allow any water to drain away from the post end. A fencing pal, also advised me never concrete to surface level and just pack soil on top of the concrete, as its kinder to the posts to allow some movement.

With regard to metal post fixings, I think fencing contractors don't rate them. They must be a swine to remove and replace. I don't know how they would stand up to the wind loading, potentially allowing for post to shear at the metal/wood connection?

My last fence posts my farther and I installed lasted 18 years, but I have some professionally installed fencing that was installed in 1988, last year I had to repair two posts with a concrete repair spur, but many are still in fine fettle.

One last thought, I have just installed an eight panel fence adjacent to row of Leylandii trees on my neighbor land. Digging the post holes was very difficult due to the roots. However, the hole were very dry due to these trees, so at last I have found one use for these trees, they keep your posts feet dry!!!

Same as this method as above but I coat bitumen up the sides of the post up to around six inches above the post that will be protruding from the ground. DO NOT paint the bottom edge of the post (the grainy end). The coating around the sides prevents water soaking in through the sides of the post. Leaving the end sitting bare in pea gravel allows any moisture that travels down the post from up top to happily drain away. If you were to paint the end of the post it would simply rot.

Also make sure you cap the posts with a square of timber or whatever you fancy to prevent rain driving through the top.

And make sure you use enough concrete to anchor the post in.

The scaffold method sounds gash and unnecessary. Although I understand why he may of tried it I don't think there's any need.

 

[dickm]

FWIW, the posts for an overhang on the front of our house are mounted more-or-less as the OP describes, except that the posts sit in a shortish (3") socket on top of the metal pole. But, the structure of the rest of the house prevents any twisting or shifting of the posts - if the cart shed is, effectively, racking about the scaffold poles causing them to bend, then isn't the solution to triangulate the various structural elements so that it becomes a rigid box? Then there would be no bending forces on the poles.
Or am I missing something?
(It's often been said )

 

[Harrris303]

Yep what I was trying to describe is what dickm mentioned, although I hadn't twigged that they were normally used when the frame is attached to another building.
My friend has done quite a lot of timber framing before and the frames have plenty of bracing etc so they are pretty rigid. Just in this one instance it was slightly less rigid than normal. I think I should probably repeat that the wobble was pretty tiny, and it was only really apparent when we were climbing about on it putting the roof on. I really didn't think it was bad at all but my friend was annoyed that there was any movement whatsoever.
Anyway from the sound of it I'll be best off looking into burying the posts in future if I do anything similar. Thanks for the useful tips on drainage and treating the wood etc. I'd never have thought to leave the grain end untreated! Cheers guys.

 

[gwaithcoed]

This is the method I have used for years. Went to my local steel provider and got 2ft lengths of 2"x 1/4 strip. These are then bolted on to the posts using 10mm screwed rod. I then dig the hole and top it with a square frame. A piece of wood is then set across the frame for the post to stand on. the post is then set upright and the hole filled with concrete. The idea being that if a post required changing I could simply remove the bolts and replace the post.
I used this at my last house where I lived for 20 years without having to change any posts, and I've been here for 17 years without any problems.

Alan.

 

[Harrris303]

Oh right thanks Alan that's the kind of thing I've been seeing while researching online. I thought they looked quite effective but I couldn't really find any trustworthy info that wasn't promotional material. The steel you used looks much sturdier than the brackets you can buy though so I might look into rigging up my own as you did.
What sort of structure did you use that method on? Was it a free-standing structure?

 

[gwaithcoed]

At my previous house it was used on 30 ft of 5ft fencing panels and now I used it to support my trellis. I've just used it again to support a B&B sign for a friend of mine. I always paint the steel with a coat of black hammrite although I don't think it would rust through in my lifetime.I have to make a notice board to go on the first tee at my local golf club and will be using the same method.

Alan

 

[Harrris303]

Great thanks for the info. Definitely going to bear all that in mind.