Excalibur Screwbolts? Are they the hold down I need?

[[1ponders]]

While installing my concrete pier 12 months or so ago I made the fundamental error of not including hold down bolts that would be anchored in the pier itself. So now I'm looking at an alternate hold down option for my pier extension.

Excalibur Screwbolts have been recommended to me by a construction Teacher here at TAFE. I was considering chem anchors or stainless steel dyna bolts.

I've not used the Excalibur system before so I'm interested in whether 5/12 or 16mm screwbolts would be sufficient to hold the baseplate of the pier extension to the top of the concrete pier.

Basic concete pier info is 360 (?) mm wide filled formatube with boxed reo from the 700x700x700 concrete footing up through the center of the pier. You can see the construction here (http://www.iceinspace.com.au/forum/showthread.php?t=30065). There will be 5 bolts, one through the center and 4 equally spaced around a 350mm wide circular base plate (6mm thick).

Will the Excalibur Screwbolst do a good enough job to hold the plate firmly without movement and if so would I need to go to 16mm or would 12 mm be sufficient.

Or would 5/12mm be overkill

[wasyoungonce]

I'm not a fan of them. I used them when building a pool equipment box for hinges (rather large heavy doors) into brick.

I found I need to back them out a few time when "screwing them in" to clear the bore hole of debris. The ones I used were Allen key & countersunk heads so the hinges could close flush.

This is a bad thing to do with these anchors, maybe it was me or maybe it was trying to use Allen head types...I couldn't get enough torque on them to drive them home in one go.

Anyway if you drive them in/out to clear the bore they tend to strip it (the bore) out! I stripped a few bores this way which really complicated matters!

I'll stay away from them in future...or at least try to ensure they are driven straight in....if possible. Maybe the bolt hex head types are better & you can get more torque???

My 2c worth

[[1ponders]]

thanks for that....appreciate it. I'm looking at the hex head ones to be driven with a socket, though they do say that if they bind to back them out and start again. Stainless Steel Dynas are looking more and more the go.

[wasyoungonce]

I should also have said that I got the impression that the Excalibur bolts tended to twist a little before turning in the bore, especially when tightening them up to final torque.

Kinda like they would twist and alot of more torque is needed to make them turn that final bit. I couldn't do this with some so some were left slightly under tensioned.

Maybe it was me but next time I do that...dynabolts!

Maybe the hex heads are better? Anyway I didn't have a pleasant time with them.

[Hagar]

If it was me I would be looking at the chem anchors as they dont have massive lateral forces applied to your pier where all the other anchor systems rely on lateral strength in the material they are going into and a pier with a relatively small sied wall thickness may be under stress and crack. Drilling the holes will be hard enough.

[mercedes_sl1970]

I've successfully used screwbolts around the house eg. for hanging a couple of decks where the brick courses were not very high and have not had any movement. As I understand it, they cause very little lateral force compared to dynabolts (excuse me if I am wrong - but this was the advice of a couple of builders). I have had personal experience of splitting a couple of cement bricks (as a test) with a dynabolt and no splitting with a screwbolt. So... I'd avoid the dynabolts in your situation, consider the screw bolt - so long as you can drill some reasonably straight holes or probably go with the chemical anchors.

[kinetic]

I'm with Doug on this one Paul.
Chem anchors would be the go.
I deal with the people who do large structural free standing
applications in my work and they also agree chem is the preference
over traditional dyna. For a pier I'd have to agree.
Dynas are only good if everything is installed as per spec.
One variable in that spec lets them down.

FWIW.

Steve

[[1ponders]]

Thanks guys this is the sorta stuff I'm after. Dynas are a concern form me if I'm not able to fix them inside the mesh cage and they are only 75mm or so from the edge