Bridge Lumber

[sdavies2000]

I'm in the process of building trails on my property and need to build a 30' bridge across a creek. It's going to be a long bridge with sills buried at each end and stringer logs spanning the creek. I have ash, cedar, aspen and maple available on my property. My first thought was to use cedar for everything but then I got reading and read somewhere you want your stringers to be hardwood. what does everyone think? the sills will definitely be cedar but what should the stringers be?

 

[mikester]

Option 1. Get a culvert and cover with dirt
Option 2. Buy a used flatbed tractor trailer deck and use that in your design.

Do yourself a favour, if you have to ask these questions then you shouldnt be designing that bridge. You will also need to talk to your local building inspector and/or roads superintendent if you are connecting to a public roadway.

You are in Ontario which means you need a professional engineer to design that custom made bridge for you.

 

[Clintock]

A span that long.. I’d buy an old trailer and take all axles and springs off. Drag across creek and level. Don’t have to worry about it floating away either if the water gets high.

 

[sdavies2000]

It’s 200yds behind my house in the bush, with nearly zero change in elevation. The banks are about 1.5’ above the creek bed. I’m not concerned with inspectors or engineers.

 

[sdavies2000]

It’s 200yds behind my house in the bush, with nearly zero change in elevation. The banks are about 1.5’ above the creek bed. I’m not concerned with inspectors or engineers.

I have considered a flat deck but it would be a bear to get back there

 

[Clintock]

I have considered a flat deck but it would be a bear to get back there

Rather deal with a bear once than fight wolves over and over...

 

[EddieWalker]

I've never built a bridge. Where I live, all those wood species would rot out in a couple of years.

I watched a bear hunting video years ago where they built a bridge over a creek up on Canada that was kind of neat. They dragged some logs across the creek with four wheelers, and then smoothed the top of the logs with a chainsaw. Then nailed boards onto the logs. It was fast, cheap and effective. For just a trail bridge in the back of your land, something like that seems ideal.

 

[Diggin It]

It’s 200yds behind my house in the bush, with nearly zero change in elevation. The banks are about 1.5’ above the creek bed.

How much current/flow is there? Does it flood higher than that? Rush faster after a heavy rain? What drives over it?

Can you consider some large diameter rock ... rip rap type stuff that will allow the flow? Think of a wet bridge type of thing where you drive over the rocks.

You might even be able to lay timbers on the rock if you need a smoother surface.

 

[deezler]

30 feet across but only 1.5' deep below the banks? Pics would help.

Does it flood out above the banks ever? Like, even once a decade ever?

 

[ROUSTABOUT]

Buy some big pipe or I beam. 30' too far for wood. Unless you pour some bannisters under it. When it breaks one day, only one side will, and someone you know will be upside down in the water with a machine on top of them. Build something good to stay.

 

[sdavies2000]

Rather deal with a bear once than fight wolves over and over...

That is actually a great quote. however.

it’s a slow moving creek that only floods out if I let the beavers have their way.

Primarily it will serve to allow foot traffic and atv’s but it would be nice to have the option to drive a tractor or skidsteer over it.

ill get some pictures today or tomorrow.

there is a very old bridge I’m currently using right now, I’ve never taken my tractor across it but it was part of the snowmobile trail so large grooming machines would have went over it for decades. All it is is 4 logs spanning the distance with supports underneath and 3x4 lumber decking.

I just want to recreate what they had here before, just not sure what kind of trees they used but I’m willing to bet they didn’t go far for them.

 

[Diggin It]

it’s a slow moving creek that only floods out if I let the beavers have their way.

Primarily it will serve to allow foot traffic and atv’s but it would be nice to have the option to drive a tractor or skidsteer over it.

there is a very old bridge I’m currently using right now, I’ve never taken my tractor across it but it was part of the snowmobile trail so large grooming machines would have went over it for decades. All it is is 4 logs spanning the distance with supports underneath and 3x4 lumber decking.

I just want to recreate what they had here before, just not sure what kind of trees they used but I’m willing to bet they didn’t go far for them.

OK, so lay enough rock to make the crossing about 10-15' wide. Build your foot bridge 4-5' wide along one edge of the rock path. The ATVs and whatever can cross on the rocks beside the foot bridge.

Only problem with that might be if the bottom is soft enough for the rocks to press into and make it necessary to keep adding more rock.

 

[Clintock]

Slow moving, 18” deep. All honesty I’d just drive across it. If it’s too boggy in bottom just get a little rock and line the bottom

 

[sdavies2000]

Slow moving, 18” deep. All honesty I’d just drive across it. If it’s too boggy in bottom just get a little rock and line the bottom

Well It gets most of its use in the winter time from cross country skiing. I have a trail groomer i tow With atv around the trails in winter so it has to cross the creek. I just want to replicate what’s already there, just wondered what my best choice of stringers are and I’d like to use the resources I already have. I’m 80% sure the stringers under the old bridge are cedar but the article I read about using hardwood for stringers had me second guesssing.

 

[PILOON]

If it is only for snow machines and skiers then simple hydro poles could suffice.
ATV and snow groomer should not be a problem.
LOL, just leave your tractor home.

 

[JethroB]

Old utility poles. Our local electric co-op used to give them away. Not sure if they still do. Good for pole barns too. And piers/docks.

 

[Sebculb]

Use full on round wood tree trunk poles. I'm sure you already know this but round tree trunks are way stronger than milled up wood. Find some nice strong hardwood trees of an appropriate size and use those.

I live in rural Costa Rica and they build some bridges around here by pouring concrete abutments on both sides of the stream. Up a good bit from the ground level in case the river gets big and a trapezoidal shape on the sides to help Chanel the water through, if that makes any sense.

Then they lay logs across the abutments. I've seen big ol' bridges that they drive trucks across. Not like a tractor trailer but a box truck or cattle truck no problem. There's some hardwoods here that are so hard the Sawyers don't like them cuz they destroy chains and bands etc. But they're great for spanning bridges.

The logs are placed together side by side, it can be three or four, and They use clay dirt to fill in the undulations. Then pour a thick concrete slab over it. Works good for a long time. I've participated in building a couple of these things since I drive a backhoe.

I dunno if that's more elaborate than you were hoping but you can definitely span 30' if you cut down a good size tree and have a machine that can drag it around and place it.