# Boardwalk. What's a safe span?



## Equismith (Jun 20, 2008)

We are putting in a boardwalk to cross over a traditionally soupy mess in a swampy area.

We'll be using 12' 2x8 joists. The deck boards will be 2x6s. Will having 24"OC joists under the 2x6s be sufficient with about 5" overhang on the edges? We really don't need overkill if we can prevent it. It will be used by walkers/hikers but is primarily a MTB trail.

1" between deck boards for leaf fall through.

Elevated about 1' off the ground.


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## cargo2k (Sep 10, 2009)

how are you supporting the joists? ie ground to joist. first thing to check would be local building code, that should give an idea.

and one inch between boards sounds like quite a bit of gap for hikers.


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## cargo2k (Sep 10, 2009)

found some stuff on the IMBA site that might help you, check out the pdf http://www.imba.com/resources/trail_building/trailbridgedetails.pdf

from the page http://www.imba.com/resources/trail_building/index.html

I would highly recommend using screws over nails to fasten the decking, wood does move, alot, enough to lift out 16 penny nails.


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## dmonbike (Jun 26, 2006)

I agree with cargo that it would be helpful to know what your footings will be. 12' long span with 2x8's will lend itself to a little bounce in the middle. 10' span would be a little better with that size board. I'm guessing you're going 36" wide on the deck. 5" of overhang is fine. Also, you should have at least 2x4 sills under your stringers.


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## ortedd (Jan 14, 2008)

cargo2k said:


> found some stuff on the IMBA site that might help you, check out the pdf http://www.imba.com/resources/trail_building/trailbridgedetails.pdf
> 
> from the page http://www.imba.com/resources/trail_building/index.html
> 
> I would highly recommend using screws over nails to fasten the decking, wood does move, alot, enough to lift out 16 penny nails.


I found that a while ago and had been looking for it again Thanks!


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## sambs827 (Dec 8, 2008)

cargo2k said:


> found some stuff on the IMBA site that might help you, check out the pdf http://www.imba.com/resources/trail_building/trailbridgedetails.pdf
> 
> from the page http://www.imba.com/resources/trail_building/index.html
> 
> I would highly recommend using screws over nails to fasten the decking, wood does move, alot, enough to lift out 16 penny nails.


you've never had screws snap? I've found that they're more brittle than sinkers, and even more brittle than deck nails and ringshanks. a 16 or 20-penny ringshank is not gonna come out easily, and will be able to withstand that wee bit of flex that is oh so common in backwoods bridges. Cheers!


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## woodway (Dec 27, 2005)

Buy the galvinized nails that have a twist in them. Once sunk, they are almost impossible to pull out.

1" gap is a little wide for the doggies who will be taking their masters out for a hike.


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## cargo2k (Sep 10, 2009)

I've had screws snap, but more often I have seen nails back out after the wood has aged, shrank or wiggled about. Using screws helps to delay that as the threads grab even after the hole has grown large enough to move a nail freely through. Using ringshanks though would be a great compromise, particularly galvanised.


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## ebxtreme (Jan 6, 2004)

cargo2k said:


> I've had screws snap, but more often I have seen nails back out after the wood has aged, shrank or wiggled about. Using screws helps to delay that as the threads grab even after the hole has grown large enough to move a nail freely through. Using ringshanks though would be a great compromise, particularly galvanised.


I hear ya.....but 6" galvanized spirals usually don't back out - even with twisted split cedar rungs. 4 per rung, of course.

EB


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## dcrowe (Oct 9, 2009)

You are probably done this build already. But it's snowing here and I am inside so I have some advice. 

Span: Your local building inspector will be able to tell to the max span for your joist and decking specs. 

5 inch overhand is more than I like to go for. At this heigh I would keep the overall width to 24 and run joists 20.5 oc that way your waste will be minimal with your decking. 

I would never, ever use screws for MTB structures, They are not like decks and walls as they get hit by all kinds of impacts in all kinds of creative ways... screws suck for shear (sideways ) strength. The best choice are ardox nails, the ones with the twist. Galvanized is better but not necessary. 

One important tip that I picked up is to dull the tips of your nails with few blows of the hammer, This causes the wood fiber to tear, not split. Hope this helps


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## sambs827 (Dec 8, 2008)

dcrowe said:


> I would never, ever use screws for MTB structures, They are not like decks and walls as they get hit by all kinds of impacts in all kinds of creative ways... screws suck for shear (sideways ) strength. The best choice are ardox nails, the ones with the twist. Galvanized is better but not necessary.
> 
> One important tip that I picked up is to dull the tips of your nails with few blows of the hammer, This causes the wood fiber to tear, not split. Hope this helps


AMEN to that, man. It irritates me to no end when people insist on using screws because it forces you to either A) assemble an entire structure near electricity and carry it to the site whole or B) take cordless drills into the woods. Fully constructed bridges are heavy, and drill batteries run out pretty quick in hardwoods especially.

Then there's also your point about the screws snapping. I've found that people hear the word "nail" they think of a plain sinker that one can easily pull out with the claw of a hammer. Note to all you folks: Even a 16 penny deck nail (the twisty kind), at less than 4 inches long, is pretty difficult to pull out and still gives a the necessary bit of flex that your bridge/teeter totter/ etc needs.


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