Pond Boss
Posted By: KristofMI Building a bridge across my pond - 01/17/22 02:27 PM
Hi Guys
New member and this is my first post. Anyway I did some search on google and this forum always shows up so I decided to join and ask here. Just recently we purchased a abandoned farm. It has a small pond on it about 50ft wide x 120 ft long. Right now it's solid frozen so I think it will be a good time to drill some holes in it and install the bridge and not get wet. So my question is how far can I span a 2x6 or 2x8 ? Bridge will be 4ft wide and we will only walk on it. Of course it will be installed on the 50ft wide side
I would appreciate any help.
Posted By: esshup Re: Building a bridge across my pond - 01/17/22 03:29 PM
Welcome to the forum!

While this isn't for bridges, this might give you a starting point.

https://www.awc.org/codes-standards/spantables/tutorial

What will you be using for columns and how will you be installing them in the pond?
Posted By: FishinRod Re: Building a bridge across my pond - 01/17/22 04:30 PM
Your question is more complicated than most people realize, but esshup has posted an excellent resource.

Further, those codes are for wood that is utilized in protected spaces. The strength of your crossbeams will always be subject to continual reduction due to weathering, insect damage, rot, etc.

It would probably be better to build a little above code and use pressure treated wood.

I also agree with esshup that you need a good plan for your support posts.
Posted By: Pat Williamson Re: Building a bridge across my pond - 01/18/22 04:19 AM
Originally Posted by KristofMI
Hi Guys
New member and this is my first post. Anyway I did some search on google and this forum always shows up so I decided to join and ask here. Just recently we purchased a abandoned farm. It has a small pond on it about 50ft wide x 120 ft long. Right now it's solid frozen so I think it will be a good time to drill some holes in it and install the bridge and not get wet. So my question is how far can I span a 2x6 or 2x8 ? Bridge will be 4ft wide and we will only walk on it. Of course it will be installed on the 50ft wide side
I would appreciate any help.
How bout a floating bridge? Wouldn’t have to sink posts except at landfalls
Posted By: DreamcatcherDB Re: Building a bridge across my pond - 01/18/22 03:37 PM
You have proposed an interesting project. Though you'll need to figure out the specific complexities on your own, I think I may be able to help point you in the right direction..well, at least A direction. There are many ways to achieve what you are asking.

The first thing I would consider is the abutments at each end. Typically, this would mean building a retaining wall to stabilize the banks. To do this you would need to drive posts in at the bank then plank the soil side of the posts. Next fill in the area nice and level using good soil then compact thoroughly. Excavate an are about 4'x4'x1' behind the retaining wall and frame a square box using 2x12's then fill the box using 21AA crushed limestone or similar, compacted every 4".

At this point, I would determine my fully required distance at the far ends of the new abutments; If it was originally a 50'-0" span it would now be 58'-0" distance.

As suggested above, I would consult a span table keeping in mind that you will want to use 0.60 pressure treated southern yellow pine lumber throughout. Given that, I would consider using 2x10 joists @16" on center. I would shoot for a relatively low modulus of elasticity so the bridge doesn't bounce nor sag over time. I would break up the spans to make optimal use of 16ft and 14ft lumber, which would give me spans of approximately 11ft and 12ft plus a short central span of about 4ft.

The depth of your pond will ultimately determine your post dimensions and material. I figure for a typical 6ft deep pond, 4x4 posts will do but you may also consider using steel beam or pipe. I would figure on no less than four pairs of posts with headers on both sides and cross bracing.

Going well above and beyond code, I would double the outer joists and stagger them to overlap by half to create straight, solid 3" wide beams. I would also add 3' block cleats to solidly join each inner joist. Last, I would block in between the joists every 8' before attaching deck planks.

I think it should be clearly stated that there will undoubtedly be specific site circumstances that must be considered; depth of water, density of soil below water, stability of soil at banks, actual vs. approximate distance between banks, local codes, insurance liability, quality of materials available, added mechanical connections required, etc,etc. This is not something you can just do on a whim and complete in a weekend but at least you have a starting point for when you consult your local engineer, builder and county officials.

I am including a sketch of what I mentioned above. Please do not consider it a plan to build from. Take my advice at your own risk.[Linked Image]

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bridge.jpg  (189 downloads)
Posted By: KristofMI Re: Building a bridge across my pond - 01/18/22 06:34 PM
I apologize for such a late reply guys. I was thinking once someone reply to this thread I will receive an email. I will use galvanized pipes and tommy docks brackets for the 2x6 or 2x8. Of course I will use pressure treated wood. Pipes will be driven in as much as I will be able to go. So I'm thinking to divide the distance into 3 sections. So... 4 pipes will be installed in the pond between both pond edges.
I was thinking about floating bridge but like the stationary idea better. The support posts I'm planning to drill thru them instead of just relaying on side bolt pressure to keep it from sliding down. This will be done of course after I level everything.
Posted By: KristofMI Re: Building a bridge across my pond - 01/18/22 06:41 PM
Some photos of the hardware I will use
[Linked Image]
[Linked Image]

I will machine a custom made adapter for my one man auger where I will be able to attach the pipes with the above points to it and drive them down as much as possible.

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brackets.jpg  (355 downloads)
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auger point.jpg  (354 downloads)
Posted By: DreamcatcherDB Re: Building a bridge across my pond - 01/19/22 01:16 PM
Based on the overall span, I don't see how 3 sections would do it and not being overly bouncy, and eventually sagging over time. I suppose, if you did it as you say, using overly long spans, and you concluded that it was not supported well enough, you could always go back and add more supports.

I am also cautious to agree with your idea to use a power auger to drive the posts knowing that at some point the points are sure to grab. I subscribe to the K.I.S.S. methodology; just spin them in by hand first and see how that goes before making the task more complicated than it may require.
Posted By: KristofMI Re: Building a bridge across my pond - 01/19/22 01:37 PM
Originally Posted by DreamcatcherDB
Based on the overall span, I don't see how 3 sections would do it and not being overly bouncy, and eventually sagging over time. I suppose, if you did it as you say, using overly long spans, and you concluded that it was not supported well enough, you could always go back and add more supports.

I am also cautious to agree with your idea to use a power auger to drive the posts knowing that at some point the points are sure to grab. I subscribe to the K.I.S.S. methodology; just spin them in by hand first and see how that goes before making the task more complicated than it may require.
I can use 2X10 joists if this will be better. Like you said I can add more supports later on or maybe just not secure the sections to pipes so they will slide up and down on the supports? And just put floating supports under the middle section?
Also I will try a simple handle first to drive it in.
Posted By: esshup Re: Building a bridge across my pond - 01/19/22 05:15 PM
The water level in a pond will rarely stay the same level from season to season, let alone year to year so I feel that mixing fixed supports with floating supports will not work.
Posted By: Hirsch56 Re: Building a bridge across my pond - 01/19/22 06:03 PM
If you mix fixed support with floating, you end up with a couple ramps at some water levels, so you need to plan on some surface treatment for traction. I might try only one fixed end that is hinged, a center float at another hinged junction, and a rolling support on the far end. Hinges are simple with eyebolts and caribiners. Ballast might reduce bouncing at the float, but that is a technique I have not tried.
Cheers, -Hirsch
Posted By: KristofMI Re: Building a bridge across my pond - 01/20/22 01:42 PM
So I will stick with fixed supports for now and then add more if needed. Hopefully I will be able to do it next weekend. Weather looks cold for the next couple of weeks.
Posted By: FireIsHot Re: Building a bridge across my pond - 01/20/22 02:23 PM
Originally Posted by KristofMI
Some photos of the hardware I will use
[Linked Image]
[Linked Image]

I will machine a custom made adapter for my one man auger where I will be able to attach the pipes with the above points to it and drive them down as much as possible.

KristofMI, looks like your pic is of Tommy Dock hardware. If so, invest in the footpads. They will keep sections from sinking, and create a nice solid stop when twisting the auger feet. I've used them for years, and had zero movement.

Also, I might check the big Orange box store. They used to have great pricing for Tommy Dock hardware and tubing.
Posted By: DreamcatcherDB Re: Building a bridge across my pond - 01/20/22 02:35 PM
I just happened across this today. It seems like it might fit your needs.[Linked Image]

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50' dock.jpg  (285 downloads)
Posted By: RAH Re: Building a bridge across my pond - 01/20/22 02:49 PM
Think that I'd walk around to get to the other side:)
Posted By: DreamcatcherDB Re: Building a bridge across my pond - 01/20/22 08:37 PM
I was more intending to let him know it was presumably pre-engineered at 50' to give him an idea of the materials required and price. $5k might feel like a deal for a pre packaged bridge system. I don't know how much he was planning to invest.
Posted By: KristofMI Re: Building a bridge across my pond - 01/21/22 01:25 PM
Originally Posted by FireIsHot
KristofMI, looks like your pic is of Tommy Dock hardware. If so, invest in the footpads. They will keep sections from sinking, and create a nice solid stop when twisting the auger feet. I've used them for years, and had zero movement.

Also, I might check the big Orange box store. They used to have great pricing for Tommy Dock hardware and tubing.
Yes they are Tommy Dock hardware. I did buy it from Depot since they had the best price on them. Forgot about the footpads. What size did you buy?
Posted By: KristofMI Re: Building a bridge across my pond - 01/21/22 01:30 PM
Originally Posted by DreamcatcherDB
I was more intending to let him know it was presumably pre-engineered at 50' to give him an idea of the materials required and price. $5k might feel like a deal for a pre packaged bridge system. I don't know how much he was planning to invest.
This does help. I would not like to pay $5K for this project. I see they divided the dock into 5 sections. So they span 10' between supports. They used 2X6 to build that one. So if I use 2X10 I should definitely be safe to span 16'. I mean even 2X6 is strong enough to hold me or my kids. But it will be little bit bouncy.
Posted By: FireIsHot Re: Building a bridge across my pond - 01/21/22 03:02 PM
Originally Posted by KristofMI
Originally Posted by FireIsHot
KristofMI, looks like your pic is of Tommy Dock hardware. If so, invest in the footpads. They will keep sections from sinking, and create a nice solid stop when twisting the auger feet. I've used them for years, and had zero movement.

Also, I might check the big Orange box store. They used to have great pricing for Tommy Dock hardware and tubing.
Yes they are Tommy Dock hardware. I did buy it from Depot since they had the best price on them. Forgot about the footpads. What size did you buy?

I buy the round 8" heavy duty foot pads. I would think any of the feet would work just fine though.

esshup and I have built 4 different docks, floating and stationary, and used Tommy Dock hardware on each one. It really simplified the process. If you decide to float the bridge, then go with Dock Builders. They have all the galvanized hardware and floats you need. They'll even calculate the float sizes needed based on static and live loads.

Consider stainless steel square head screws for use on the pressure treated lumber. Expensive, but they never rust.
Posted By: esshup Re: Building a bridge across my pond - 01/21/22 05:09 PM
If using the floats from Dockbuilders, don't put the plugs in them until you are ready to put them in the water, or at least get them out of direct sunlight after you put the plugs in.......

Al, is that one still holding up?
Posted By: FireIsHot Re: Building a bridge across my pond - 01/21/22 05:11 PM
It seems to be. Best I can tell, all's well.
Posted By: KristofMI Re: Building a bridge across my pond - 02/14/22 02:17 PM
[Linked Image]Finally was able to start on the project. Was able to screw the pipes in only 10" then I hit a clay bottom. We tried to use the longest pipe wrench we could buy at local store and it won't go any deeper. Both end sections just lay on the ground for now. I will wait till spring and then install 4x4 on both ends and screw them in.

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Posted By: FishinRod Re: Building a bridge across my pond - 02/14/22 02:31 PM
Thanks for the update!

I would highly recommend putting a cheater pipe on your big wrench while you still have ice on the pond. You and a couple of teenagers on a 6-8' cheater could put significantly more torque on your pipes. (You might even have to use a little "feel". I suspect three guys on the cheater could actually twist off one of your augers on the bottom if it is sufficiently stuck.)

The other bit of advice is to put a cap on your pipes and have someone tapping with a baby sledge hammer while you are turning the pipe. A little downward "shock" force will also help you make depth in the clay.
Posted By: KristofMI Re: Building a bridge across my pond - 02/14/22 02:53 PM
I was thinking to rent one of those gas powered post drivers. My friend used it to install his well. I'm afraid if we use the cheater pipe we will unscrew the pipe from the auger tip and then loose it forever. Will call the Tommy Docks today and see what they think. They recommend 12" deep so I assume 10" will be close enough especially that it is a clay bottom. First time ever I drill in ice with auger. Took some down pressure to get it started and then it went okay. Got my boots wet anyway grin
Posted By: Tbar Re: Building a bridge across my pond - 02/16/22 09:01 PM
Double those boards maybe?
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