Traditional post to joist versus surface mounted post

by Bob
(Missouri)

I have been reading through the text on the different tests for the 6x6 and 4x4 Titan anchors. How do the test results compare to the less modern,traditional methods of connecting rail posts (notching & carriage bolts for example)?

I installed my first 6x6 anchor yesterday and it seems VERY sturdy. I have a piece of 2x12 treated lumber secured to the surrounding joists and rim joists with 8 - 3.5 inch deck screws for added support underneath the deck boards. I would be curious to see what the force rating of the traditional methods are.

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Sep 08, 2011
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starstarstarstarstar 		Both lead to code compliance
by: Editor-Rich Bergman

A 2005 test done at Virginia Tech University did a bunch of tests on joist mounted single 36" posts. Those using notched and un-notched posts with lags or bolts and resisted about 180 lbs and 240 lbs each. Using joist to rim joist metal connectors and through bolts the loads averaged somewhere between 600-700lbs. Great results.

Joist connected posts benefit from a longer resisting arm and cross grain fastening.

The physics dictate that the top end load when compared to an identical sized post using the internal wood post anchor will always be greater because the resisting arm is longer than with a post anchor.

In addition the post anchor has fasteners going into the post bottom, parallel to the grain so holding power will never be as strong as a cross grain bolt.

But that's not the end of the story as some may wish to suggest.

So that is what we give up - a little bit of top end performance but in return we gain so much more.

We get a beautiful, wonderful looking clean post to surface connection that everyone lusts after.

We get ease and speed of installation and complete freedom to locate posts wherever on whatever surface you want.

We eliminate notching deck boards, and posts if you still use that out dated technique.

We get longer post life because we eliminate wood to wood contact.

So the benefits are great while the slight reduction in one on one comparative strength to joist mounted techniques is irrelevant.

Why? Because both methods get you beyond the building code standards (IRC).

Our 4x4 anchor using 36" posts has recently passed the rigorous AC273 testing regime and results will be published shortly. We load the top of a single post in a rail section to 200 lbs, measure deflection and then load to 500 lbs, hold for at least 60 seconds and they we go up to destruction for fun.

Our single 6x6 anchor using a 42" post, completely free standing resists over 500 lbs. Using the test mentioned above it goes well over 700 lbs. So you are in very safe territory.

The fact that a properly installed post to joist would perform higher is irrelevant.

None of this is to disparage or render obsolete post to joist techniques because they work well and will be around forever. And they may well be your only option is some cases. You just don't get the benefits I mentioned that most people want for their home.


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