Concrete screws vs Lag Bolt/Shield Anchors - is one better?

by Chris
(Vancouver Island)

I see that you recommend and sell GRK Caliburn pan-head concrete screws for installing Titan post anchors on concrete. I was wondering how these concrete screws compare to using a typical lag bolt & lag shield anchor? Does one method offer advantages over the other?

I’m installing a 42” high railing on my raised concrete porch and am planning on using four fasteners per Titan post anchor (4x4). I’m interested in maximizing holding power, ease of installation, and having the ability to remove and refasten the posts in the future.

While GRK’s website alludes to the ability to remove and replace their screws, should I expect a reduction in holding power over time with reinstalled screws? Would a lag shield anchor work better in this regard?

Would either fastener provided better pull out strength when installed in seasoned concrete or would they be roughly equal? Thanks for your help.

BTW, I love the Titan post anchors. Sharp looking, easy setup and strong! Nice product.

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Jun 16, 2013
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Engineering has explained a lot of this
by: Editor - Rich Bergman

This is a great question.

Having now done a complete and extension engineering program for residential guardrail use for all of North America I can fill you in on a lot of the technical details we have learned. Lags and shields are fine but less visually appealing so you would probably want to cover the base with a post skirt.

The GRK concrete screws and others like them are in my opinion the easiest and best solution. Yes you can remove them easily as I have done and re-screw them in and unless ice gets in there and cracks up the concrete seems to hold fine the second time as well. However I would want to defer to any engineering guidance from GRK or Tapcon to know the truth on that.

But all of this is really a bit of a moot point know that we know the weakest link in the entire system is almost always the wood post. The most common wood species used with the Titan Post Anchor are in the SPF category, Spruce, Pine Fir. So our engineering guidance applies to any species whose densit is equal to or greater than the lowest within SPF. Western Red Cedar does have a higher density than a number of spruce so it applies as well.

So even if you have a super bullet proof over the top base to concrete screw it doesn't matter because the post would start to break apart before the anchor is pulled off the concrete.

We test to a certain safety factor in the US and Canada. We provide the guidance to use our product in compliance with meeting the safety factor.

So if you use a lag and and shield system, four is enough and just cover it with a post skirt. Or use a concrete screw. It is more about your preference rather than will one or the other make or break the building code compliance of the post and anchor.

As an example, we tested the post anchor using Ipe which is so hard. Using Ipe would could not break the posts off the anchors. We ended up each time pulling the anchors off the deck surface.

So to maximize a railing system using Ipe, you would have to us much stronger deck or concrete screws to achieve optimum load values. But that railing section was taking a 900 lbs horizontal load easily.

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