Attaching Guard posts to deck joists - DIY Chatroom

rocketdoctor · 11-07-2009, 03:20 PM

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.

CustomBuild · 11-09-2009, 02:28 PM

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.

rocketdoctor · 11-09-2009, 08:02 PM

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 · 11-10-2009, 07:53 AM

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

Thurman · 11-10-2009, 08:16 AM

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