Pond Boss Forums GENERAL QUESTIONS Property Projects & Construction Dock width suggestions

I was able to get some used dock for cheap. I have 2 3ft wide sections and 2 4ft wide sections. They have the alluminim siding and wood slats. Wood needs to be replaced. I am asking if a 3ft or 4ft is a better width to avoid sagging? We like the width of 4 ft but I’m worried that will start sagging more/quicker than the 3ft. Attached are pics. If both will last about the same without sagging then we would lean towards the 4ft. My personal opinion is the 3 ft woukd work much better.

It will not let me attach pics. The dock has the alluminum rails on the side and wood slats across. There is no aluminum center bar just a wood stringer

What size is the wooden joist in the center? You really don't want a span of the deck boards more than 24". 16" would be better.

It’s 5/4 x 3 wood. On the 3 ft there are 2 stringers. On the 4ft there are 3 stringers. Both have old wood on them and the 3 ft is significantly better than the 4 ft there is almost no sag to it with older wood. The 4 ft has a lot of sag but the wood is in worse shape. I would use 5/4 x 6 treated pine for the new slabs.

May I suggest that if you are buying new top deck lumber, go with (treated) 2"x8" tongue and groove. The boards are much stronger than 5/4"x6" (which I think of as "deck size") and stronger than 2"x6", plus with the T&G the boards help support each other. I have one 2"x8" T&G dock and one 2"x6" dock; the former has a LOT less sag despite being 2" wider. I have seen enough 5/4"x6" treated wooden fence problems that I never considered it for docks.

Thank you for the suggestions. I ended up going with 3 ft and it’s solid.