I'm in the process of designing my floating dock on 55 gal barrels. 2x8 joists, 5/4" x 6" deck boards, 14' x10' with a 4' wide gangway 12' long. I have seen some nice corner brackets at Menards and online but they are not cheap. Do most people use corner brackets to stiffen up the joist structure of their dock or just rely on the deck boards to add stability? I have built many decks on land and know how to build a structure. With a land based deck, given the design and posts that were set in concrete there was no need for any corner bracing. Thanks for your advice!!!!

When I built mine using barrels it worked out pretty well and is now 5 yrs old. I have had to replace 3 or 4 barrels in this time frame due to rust. For me I just float it to the bank and use the front end loader on my tractor to pick it up enough to slip a barrel out and replace it. So, I would suggest u set it up to be able to replace a barrel or three over time or spend that extra money on floats that do not rust and do something else to the corners. I did not use corner braces and have had no problem so far with the corners. Knock on wood!

I had a metal shop make me some out of 3/16 th steal. They will rust but they are wider than the big box ones (7x7), so where you bolt them to the corners you are farther from the edge.

I struggled with the cost of the components and tried my best to figure out a way to avoid them. Making them myself, having them made, not using all of them,stealing them (not really), but in the end I figured that the Menards prices were the best and constructing it with all the braces would lend to the longest life possible. Aside from having the right scrap iron on hand already...just the cost of the steel to DIY would get pricey. I don't want to build this thing again..it hurts too much as I get older to even think about it. And, they come hot dip galvanized...nothing better but stailnless steel and talk about expensive. He's a photo of my dock going togehter and you can really see all the places where the proper brackets will resist the twisting that a floating dock is subject to...it's got braces at most every wood joint and one on the inside and outside of the corners...

I did basically the same thing - 8x8x3/16, but bought the steel and fabricated the brackets in my shop.
Made the brackets for the mud poles too.
Between the cost of the steel, electricity for the welder, and paint, it was pretty much a wash on the cost vs. buying factory-built brackets from Menards.