Blocking for 45-Degree Decking with a Picture Frame


Old 07-15-20, 07:21 AM
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Blocking for 45-Degree Decking with a Picture Frame

Hey everyone! Iím planning out a new deck for my home and am looking for some advice on the blocking. Iím planning on using Trex Composite Decking with two deck boards running around the border on all four sides as a picture frame. I feel I have a good understanding on the blocking requirements for that.

Where Iím struggling though is how to do the blocking to place the remaining deck boards at a 45-degree angle. The joists run perpendicular to the house.

Iíve attached a quick sketch with where Iím at so far in the planning process. I wasnít sure if the standard is to throw more 2x10 blocking and toe nail it in, use joist hangers, try to stager it like my mid-span blocking or something else? I even though of putting two 2x8ís in there staggered with a 2x4 over top, but then I thought thatís when I was overthinking it.

If anyone has any experience with doing 45-degree decking with a picture frame and can offer some advice for how to block the framing where the angled decking meets the picture frame I would greatly appreciate it.

Thanks in advance!

Sketch of my framing plan.
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Old 07-15-20, 08:26 AM
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You will need blocking wherever boards end. So, you will need a perimeter of blocking where the diagonal boards meet the picture frame. Then you need to figure out if you will be using full length boards for the field or if you will be piecing it together in which case you will need blocking for those seam locations. A block here or there in the field can be toe nailed but your perimeter where you need continuous coverage I'd go with hanger brackets so you can keep your block in line with the ends of your 45į board ends.

Depending on how fussy you are you might even want blocking along the edge where your picture frame boards meet the 45į boards. Even though 16" spacing is approved by all/most deck board manufacturers there is still a bit of give when you step on the edge of the board. Ordinarily it's unnoticed because the board next to it will give as well. It can be noticeable (noticeable, but not bad) if you step on that joint, between joists where the picture frame and 45 boards meet. The 45į board's end will be completely supported while the picture frame board can flex.

One thing I've seen done that I don't like is composite deck boards at a 45į angle over studs 16" center to center. It over spans most brand deck boards so I'm glad to see you've planned up front to go with 12" spacing. That is a good call and your deck should remain nice and flat for years.
Old 07-15-20, 08:28 AM
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Old 07-15-20, 10:13 AM
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Thank you so much! I was also leaning towards the hangers but wasnít sure if I was just over thinking it or not.

the good news is that Iíll only need the blocking where the 45ís meet the picture frame as the decking will run end to end. Thatís actually why I wanted to do the 45ís so I could eliminate a bunch of butt joints.

I was also worried about how the picture frame would feel at the 16Ē spacing. I talked myself out of it but now you have me re-thinking it. Do you think it would be better to just do 12Ē on center blocking there? Or another option I just though of since I have a double picture frame would be to just sister up that first joist off the edge. Iíd still have the issue on the outside one but since the railing will also be there it may not be noticeable?
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