Decking Support Posts

[scubapete]

So, having read almost eveything on deck posts/joists and looked at the excellent guide http://www.ultimatehandyman.co.uk/diy/decking/index.htm, I have a question.

The Ultimate Handyman shows a picture with posts positioned every 1m with joists attached to these. However, there are joists between that are not attached to any posts - just the bottom frame and the top ledger. What's going on? Why doesn't every joist need supporting with posts (of flags/breeze blocks)? Won't the unsupported joists bounce?

 

[Thermo]

the rigidity of the frame will allow the supports to be spaced out so you dont need them at every junction.

 

[Pinnacle]

Once you put your noggins in place between the frame, it will be very strong indeed.

 

[scubapete]

Here's an image of my plan - just ordered from the timber merchant.

DeckPlan

• scubapete
• 16 Jun 2009
• 2

(I refer to perpendicular joists as those that run perpendicular to the house running top to bottom of the image. Parallel joists are those that run across the image, parallel with the house.)

Went for the maximum joist size I can fit in the space: 175 x 47. I wanted 125 x 125 posts, but they didn't stock them and was offered some machined ones at 115 x 115.

My theory is that by using bigger joists and posts, I can maximise the clear spans between posts whilst maintaing strength and rigidity.

I was/am thinking about upgrading the posts to 150 x 150. I could then half-lap the posts running down either side of the frame. Those two outer frame joists would then rest on (and be bolted) to the post. I'm 'borrowing' this idea from the load bearer approach for which I just don't have enough depth available.

Those two outer frame joists take all the load from the parallel secondary joists, so I'm wondering whether my theory has any merit? Or just over-kill?

Any other comments? Much appreciated!

 

[WabbitPoo]

I haven't looked at your plan - the reason being that you are stressing way too much about it!

Don't over-engineer it - if it moves when you have built the frame, add more supports and/or more joists and/or more noggins.

Its not like building a house - just keep it simple!

PS I admire your ambition to getting it all just right.

 

[scubapete]

Yep, I'll accept that. Just trying to get out of digging a few holes really. Materials ordered (plus an impact driver as a reward for myself). Will let you know what happens..