Attaching Guard posts to deck joists

rocketdoctor

I am bolting the 4x4s posts to my deck rim joists and plan on blocking it with another 2x8 on the outside. I am going to put siding on the outside of this 2x8 so the fasteners have to be flush. Can I countersynch the holes in the 2X8 so the bolts are flush (needs to be about 1"). Or should I just bolt through the 4x4 see the 2 figures below.

Also I plan on using the simpsons Dtt2z hold downs for the bolts as well.

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CustomBuild

If this is an existing deck, the rim joist already in place is the structural member. If you are worried about compromising the strucural integrity if the new outer board; you might, but you shouldn't worry about the overall strength of the deck. If you are worried about having a wobbly handrail, the best you can do is attach a post to the rim without attaching the outer board. Then give it a good shake. If it wobbles more than you would like, then bolt through the outer board, too. I would add blocks in between the new rim, and the old rim. Here's a diagram.

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rocketdoctor

thanks, Its a new deck, originally I was just going to bolt the gaurd posts to the rim joist and run decking up to the guardrail. I decided since then to run a border around with my decking material to give it a nicer finish so I need to add this additional rim joist. I was planning on doing the blocking. So should I countersynch the bolts in the 4x4 to allow me to fasten the additional joist to it.

CustomBuild

The more wood bolted together will help stabilize everything. I think bolting through the outer joist would be preferred.

Thurman

IF you are planning on using a 2 x 8 on the exterior as in picture #2, one alternative I have used would be to counterbore the exterior 2 x 8 using a Forstner type bit only deep enough for the bolt head and washer to fit into. This will allow you to bolt the 4 x 4 to the inside 2 x 8 securely, then use the exterior 2 x8 to cover the bolts. Use exterior grade screws to secure the exterior 2 x8 to the 4x4's, then use exterior grade screws going through the exterior 2 x8 and the blockers into the interior 2 x 8 board. This makes a very secure structure. Then, IF you still want to place a type of siding on the outside of the exterior 2 x 8 for aesthetic reasons, you may do so. Good Luck, David