How to fix the blocking to the main joists of deck?

[Michael80]

Hi All,

Currently building the frame for our new deck and planning to use composite boards. I'll be doing a double picture frame and double breaker board in the centre.

I was planning to use a "ladder joist" to support the picture frame and the breaker boards but I'm not entirely sure what's an acceptable way to fix the blocking to the main joists. Would 4 x 75mm framing nails through the main joists into each piece of the ladder blocking be enough? The picture frame and breaker boards would be supported in their entirety by the blocking. 

Picture attached to help explain. 

Thanks,

Michael

[Jason]

Sounds like an exciting project @Michael80. 

Let me tag our resident Bunnings D.I.Y. expert @EricL for his thoughts on your plan and recommendations for the fixings. Other helpful community members like @Jewelleryrescue, @Adam_W and @DIYGnome might also like to join in the discussion.

Jason

[Michael80]

Thanks Jason. 

I forgot to mention in the original post, but the joists and blocking are all 190x45. 

[EricL]

Hello @Michael80 

Thanks for posting that diagram of your decking frame. Your configuration for the blocking is excellent. It is very similar to this blocking configuration in this discussion - Low-level composite deck over concrete and soil by @oninpena. I suggest using Buildex 12g x 100mm 8 TPI Climacoat RapidDrive Treated Pine Screws - 50 Box or Zenith 14G x 100mm Galvanised Type 17 Batten Bugle Head Timber Screws - 25 Pack. My best advice is to make sure to drill pilot holes to prevent twisting the heads off.

If you need further assistance, please let me know.

Eric

[Michael80]

Thanks @EricL, I really appreciate the help. The low level deck you linked is a great example of what I'm trying to do. 

Would two screws into the each end of the blocking be sufficient to support it and the decking boards?

I did have another question regarding the blocking if you could help. The deck wraps around the house in an L shape. For the picture frame I'll need to attach blocking to joists that will be hard up again the house (just 10mm for ventilation / drainage). I won't be able to get behind the joists to drive screws into the blocking. I've attached an image of the plans with the two joists circled. 

What's the best way to attach the blocking in this case? I was thinking either joist hangers to support the end of the blocking facing the house, or just pre-assembling the joist and blocking first before moving it into place and fixing the to the bearers. Hope that makes sense! 

I considered toe nailing the blocking from the front side but wasn't convinced it would be strong enough to support the picture frame and people traffic in the long term. 

[MikeTNZ]

Hi @Michael80,

With respect to this deck, what sort of height will it be above ground level, on the outside perimeter of the deck?

I note you said it was going to be a low-level deck, is the ground under the deck flat or is it sloping away from the deck?

I have a built a lot of decks for friends and family over the years, I'm not a builder, but they are reasonably "easy" to get

your head around as to how things should fit in place.

Personally, if you are going to build a ladder joist, you need to use stainless steel Tek screws that are made for treated timber, these have a very sharp thread on the end and you should use these for your joist hangers, as opposed to nails or other screws that could pull out over time.

I insist on these screws for anything below the surface of the deck itself, you can use anything you like for the stuff above the deck, but once it is enclosed, you need to know that everything you've fitted is not going to fail, over time.

Also, if you need further help, by all means, throw another reply or thread up here, I'd be more than willing to help you out.

Cheers,

Mike T.

[Michael80]

Hi @MikeTNZ 

Sorry for the confusion. I was referring to the low level deck EricL linked to as a good example of the picture frame / breaker board layout I'll need. My deck is not at ground level, the finished floor height will range from 60 to 150cm from the ground. 

Thanks for the tip on the stainless steel screws. It's probably a good idea. The rest of the frame is built to sit directly on the member below (e.g. joists on top of bearers, bearers on top of posts), but the blocking for the picture frame and breaker will be supported by the fixings only. I can see the wisdom in using something a bit more robust. 

thanks,

Michael