Another Bridge Thread

[Jim Timber]

A 24' 24" steel culvert costs about $400 around here. You could get a bunch of fill dumped where there's good access and build it up for well under your 1K budget. Class 5 is about $200 a 12yd truck delivered in my area, but we have taconite tailings which are better road base and won't wash out if crested, and those are $185 a load.

 

[LD1]

Any pictures of the area?

Lots suggesting culverts. I would want to see the area first before offering that suggestion. You are wanting a 10' long bridge. Even 3 culverts @ 24" diameter may not be enough.

And how deep is the crossing. A 24" culvert with 12" of dirt on top is gonna make the crossing 3' high. If the crossing is shallower and wide, you may never use the top half of the culverts as the water may just go around, and they dont flow near the water an open bridge will

 

[tennesseejb]

I will be down there this weekend and will take some pictures of the actual area I want to cross. The banks themselves are about 4' deep and about 10 feet across (probably closer to 8 at the water taking into account some slope). Water is normally about 12-16" deep. I'll measure it more precisely when I'm back down there. But that's why I'm concerned about using multiple culverts because it creates one or more points where junk in the creek can get trapped and back up... making a little **** over time. So there is a maintenance component that I'm not excited about.

The trailer is functionally (and probably effort wise) a good option, except when I run revised numbers based on KennyG's data, I get a lower $ figure than I original had, and trailers seem to be quite a bit more than that.

Here's what I have on paper currently:

(12) 2x12x16 PT boards (~$30/ea or $360 total): 10 to use as beams, and 2 to use as cross bracing between beams
(35) 2x6x8 PT boards (~$5.50/ea or $192.50): for decking ... will probably be a couple less since I'll leave some space between the boards.
(8) 8' railroad ties ($14/ea or $112 total): to set the bridge on and to use as end caps... I would taper the 2x12 down to the rr tie at each end and then backfill to the RR tie so my 2x12 is not buried.

Total this comes to $664 for lumber, which admittedly does not include any railing or hardware, but we are still quite a bit less than the original guestimate.

It may be that a killer deal comes up for a trailer, which I would strongly consider . And I have found steel i-beams periodically... just never been ready to pull the trigger when they came up... but that would probably be a great option as well. Thanks for everyone's willingness to share. I'm pretty exited to figure out a plan and get something going.

JB

 

[Jim Timber]

Any pictures of the area?

Lots suggesting culverts. I would want to see the area first before offering that suggestion. You are wanting a 10' long bridge. Even 3 culverts @ 24" diameter may not be enough.

And how deep is the crossing. A 24" culvert with 12" of dirt on top is gonna make the crossing 3' high. If the crossing is shallower and wide, you may never use the top half of the culverts as the water may just go around, and they dont flow near the water an open bridge will

I spanned 250' with mine. It's not that big of deal. Make sure any of it's legal though. You might need a permit.

He's already saying the road in is soft, so maybe building it up into a proper road would be the best possible outcome.

 

[Luke'sScreenName]

Oh I'd definitely assume it's illegal. Be careful what you ask about.

 

[Jim Timber]

You're allowed all kinds of exemptions. It's not always illegal when permission is sought.

My road crosses 100% type 7 wooded swamp. Cost me a $100 permit for silvicultural exemption. With that exemption granted, I can turn it into a personal use access road for a $300 permit and the wetland bank credits for replacement (because it's in the riparian impact zone of a lake) with a 100% chance of that application being approved - since using the road for personal ingress to the land-locked parcel becomes the least impact option to the wetland.

It's all in how you use the rules of the game to your advantage.

I approached the TEP members prior to going the exemption route to make sure they didn't think poorly on my approach of doing this route vs the personal use permit first. Better to have everyone in your corner before you start than going in blind to find you have an obstacle that now doesn't want to favor your desired outcome.

 

[Everhard]

I spanned a similar distance on my property - think it's 12-14', can't remember exactly now. I used pressure treated 2 by 8's for the deck boards and for the beams I used what was local! I cut down a couple trees, not exactly the best kind for the job (Poplar!) but I went large with them (12" diameter minimum) and with my chainsaw made them flat on the top end, laid a couple perpendicular for the main 2 beams to sit on that crossed the creek. My little tractor with a 45 gallon drum of maple sap and over 800lbs of counter weight hanging off the back weighs in around 3500lbs and when I park it on the bridge I've measured zero deflection.
Yes the bridge won't last for ever (I did paint on the pressure treat stuff to help the logs from rotting too quickly.) but when the time does come one day I'll replace the beams with a couple more. It's now 3 years old and doesn't show any signs of wear yet. I made sure the logs are not in dirt so that helps them from rotting too quickly.

If you're only looking to have a bridge last 12 years as you mentioned I'd definitely look for a simple/cheap solution and save up for a more permanent option that you'll be happy with down the road.

Also how long have you been on the property - are you 100% sure it won't flood and wash away what you build? My father and I built 3 different bridges on the property I grew up on the last one is still standing today and that's 30+ years ago now that we built it. The first 2 weren't built high enough to deal with the flooding.

E.

 

[tennesseejb]

Thanks Everhard,

It would save a good bit of money to do it with local logs. I even scoped out a few near the bridge site, but I've gone back and forth on using them. The main logs on the property are cedar and shag bark hickory. I've read that while the hickory is hard, it's not ideal for long lasting in that condition. Cedar seemed/seems ideal, but I get conflicting stories about whether the log as a whole is good for this sort of use, or if I have to mill the outer of wood and get to the red stuff in order for it to last. Then comes the question of how thick they need to be. Are there the equivalent of span tables for live logs? Would cedar be the best choice?

You are right though... this is not meant to be the permanent bridge.

We've had the land for about 1.5 years now... To be fair, I couldn't say that there wouldn't be a storm large enough to cause the creek to climb over the banks, but what I've seen so far is that it get's out up stream and then again downstream. If we had rain like we did in 2010, then all bets are off and I expect I'd be looking downstream for bridge parts.

Merry Christmas all!!

 

[Travelover]

My local metal recycler resells metals at a markup, but scrap steel beams are dirt cheap right now. Might be worth checking to see if they have anything and will resell.

 

[KennyG]

Cedar seemed/seems ideal, but I get conflicting stories about whether the log as a whole is good for this sort of use, or if I have to mill the outer of wood and get to the red stuff in order for it to last. Then comes the question of how thick they need to be. Are there the equivalent of span tables for live logs? Would cedar be the best choice?

Not sure about using cedar as a structural member. It's durable (as long as it can dry out after getting wet) but my impression is that it's strength isn't great. I found some reference info that would indicate it's close to but a little lower than pine and fir.

Beam capability is related to the area moment of inertia. For a rectangular, that's calculated as (width x height cubed) divided by 12 or I=(w x h x h x h)/12. (Sorry, I'm not sure how to do superscripts here. For circular section it would be pi x diameter to the fourth power divided by 64 or I = pi x (d x d x d x d)/64. Two beams with the same I would have the same strength.

Let's say we have three 2 x 12s. The actual dimensions are 4.5 x 11.25. Then I = 534. We can solve for a circular beam and get d = 10.2 inches. Therefore, a 10" diameter log would replace three 2x12s if the wood strength is equal.