Carriage bolts for treated lumber

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Forum topic by Eric posted 04-16-2013 10:45 PM 13166 views 0 times favorited 7 replies Add to Favorites Watch
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221 posts in 2508 days

04-16-2013 10:45 PM

Topic tags/keywords: zinc galvanized carriage bolt treated swing set outdoor

We moved last October. (I hope to update shop photos soon.) My first outdoor project is re-constructing the kids’ swing set we moved in large pieces. The carriage bolts that came with the original kit were badly deteriorated.

As I re-build, what is the most appropriate metal-type for AC2 pressure treated lumber. I don’t want the expense of stainless so do you prefer zinc or galvanized?

-- Eric

7 replies so far

View crank49's profile


4030 posts in 2968 days

#1 posted 04-16-2013 11:29 PM

I just checked the engineer’s bible (McMaster Carr) and compared 4 popular materials, bronze, stainless steel, hot dipped galvanized, and zinc plated.

All bolts I checked were 5/16” x 2” long.
Bronze = $2.00 each
Stainless = $1.50 each
Hot dip galv. = $0.20 each
Zinc plated = $0.10 each

Given those numbers I would say hot dip galvanized would be the best value by far.
HD galv should last about 7 times as long as zinc, and only cost twice as much.

View Eric's profile


221 posts in 2508 days

#2 posted 04-16-2013 11:48 PM

That’s kind of where I’m leaning…. galvanized. any other opinions?

-- Eric

View kdc68's profile


2657 posts in 2273 days

#3 posted 04-16-2013 11:50 PM

+1 for galvanized

-- Measure "at least" twice and cut once

View 1thumb's profile


78 posts in 2153 days

#4 posted 04-16-2013 11:55 PM

I used to design and build wooden playsets. Hot dipped galvies

View ajosephg's profile


1880 posts in 3558 days

#5 posted 04-17-2013 12:08 AM

Might want to read this. The bottom line seems to be that galvanized will eventually fail, leaving two alternatives. Stainless or Polymer coated.

-- Joe

View Eric's profile


221 posts in 2508 days

#6 posted 04-17-2013 12:39 AM

Eventually… anything and everything will fail. Haha.

Speaking of coated fasteners- I plan to used coated deck screws. The galvanized screws supplied with the kit (about 7 years) ago were practically nails- lacking nearly all their threads. The coated deck screws ought to address this. Thanks Joe!

For the structure 4×4s, etc.. I think I will use galvanized carriage bolts. By the time the 5/16 thick carriage bolts fail, kids will be done with the swingset. The 7-yr old carriage bolts were still sound… just rusted nuts so tight my impact wrench wouldn’t break them free. A few of the old posts are going to the burn pile because of this.

-- Eric

View juniorjock's profile


1930 posts in 3762 days

#7 posted 04-17-2013 12:43 AM

Any bolt with a head on it (un-like carriage bolts) would be okay. At least you’d have something to get a wrench on when you need to change it out. Like they said, nothing lasts forever.

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