Fixing a 75x75mm Wooden post to a 75x75 Concrete post.

[James3670]

I am putting up Willow 'Hurdles' as a 24' fence. There are existing concrete posts that I wish to attach the fence posts to.

Any advice or ideas on the best way of fixing the posts to the concrete would be greatly appreciated. I was thinking either sleeved anchors, but wondered if rawl plugs and 100mm screws would be strong enough, I only need to attach 3 posts, any ideas on screw size, which colour rawl plug etc.
Hurdles are 5' high.

Cheers.

 

[JohnD]

what shape are the posts? have they got holes in? If you drill them they may well crack.

 

[James3670]

what shape are the posts? have they got holes in? If you drill them they may well crack.

Both types of post are square section, I was going to drill a hole in the concrete posts at 90 degrees to the existing ones, far enough away not to be a problem (4"). The concrete ones are council type, and in very sound condition thanks for the interest.

 

[JohnD]

if they already have holes, you might consider putting eyebolts through them, with a large washer on each side under the ring and the nut. I think this will reduce the risk of cracking. The factory holes are made by casting a wooden plug into the concrete mould, and knocking it out when set.

 

[James3670]

if they already have holes, you might consider putting eyebolts through them, with a large washer on each side under the ring and the nut. I think this will reduce the risk of cracking. The factory holes are made by casting a wooden plug into the concrete mould, and knocking it out when set.

I do see what you mean about utilising the existing holes, it's possible I could use them in some way, they had steel wire through them originally, and therefore run in the same direction as the fence, they are small though, about 8mm in diameter, so I would need galvanised wire or similar to bind the two posts together, I think locking the two posts would be sturdier though? Good info on the casting technique by the way. Cheers.

 

[JohnD]

I wonder if 8mm galvanised studding would fit? You could fix brackets or posts to it with galvanised nuts. I use studding on my fence posts as it is much cheaper than bolts. It does rust when the zinc wears off though, so paint it.

 

[James3670]

I wonder if 8mm galvanised studding would fit? You could fix brackets or posts to it with galvanised nuts. I use studding on my fence posts as it is much cheaper than bolts. It does rust when the zinc wears off though, so paint it.

Thanks JohnD, I am going to stick with the rawl plug and screw method, a friend of mine has done it, and it's stayed up for a few years, so hopefully mine should see my mother out!

 

[toomuchtodo]

I have a similar issue. I'm about to build a fence along a boundary that currently has concrete posts and weld mesh wire. The posts are solid and are all in very good condition. They kind of vary in height between 4 & 5'. I'l be using these posts to anchor 4x4 wooden posts to and then adding rails and finally feather edge. Fence will be about 7' so I was concerned about the wind loading on the new fence.

I've looked into as many options as possible and using another post that will not be part of the new fence, have tried out a few options.

Coach screws and nylon plugs held the post in place but don't seem that secure. It was possible, with some force, to get the wooden post free of the concrete post.

Sleeve anchors with protruding bolt worked a treat and there was no moving the fence post at all. However, the cost of them is huge. I'll be using 3 fixings per post and there are a total of 26 posts so cost is a factor in anything I do.

I considered other fixings with varying costs before I finally had a brainwave. Stud Iron. Essentially threaded rods normally used with resin fixings.

I picked up some M10 rods, drill through wooden post and concrete post, washer and nut on one end of rod, pass through hole, washer and nut on other end, tighten and cut off excess. They're not going anywhere. As an added bonus, there's no expansion within the concrete so no risk of cracking the concrete after drilling carefully.

It seems the most secure method for what I need and is by far the cheapest option at about £2 per post.

I'm not going to know if the wind load will be a problem on the concrete posts until I've actually got the fence erected but from my experience of removing some other concrete posts which are in the way I don't think it'll be a problem. They're well buried about 3' in and are surrounded with a huge amount of concrete so fingers crossed.

 

[toomuchtodo]

I've just re-read the thread and realised that JohnD has suggested exactly what I'm gonna do!

If I'd found this thread when I started planning it would've saved me a whole lot of head scratching!

 

[James3670]

I've just re-read the thread and realised that JohnD has suggested exactly what I'm gonna do!

If I'd found this thread when I started planning it would've saved me a whole lot of head scratching!

That's ideal then, I am new to this forum, and should look around a bit more. A good result in the end.