Need Bridge (deck) input

dan_m

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Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
I have a creek that crosses the middle of my back yard and I'd like to get my BX2380 across it and due to cost, I'm building a bridge vs doing a culvert. After speaking to county engineering and fire marshall, I can build a bridge without permits (Just had to agree in wring the bridge will not be used for commercial traffic such as a rental, wedding venue, etc). If the bridge were to be used for anything but personal use, It would have to support the weight of county fire equipment and be permitted and engineered.

The bridge will be 8' wide (end to end, hand rail will take a way from the actual width) and 20' long (ramp on each end (far side bank is higher than near side)

So far, I have the 4 x 24" round footers (2 on each side of the creek) done using 5000psi concrete. Running across the creek (girders) between the footers (2 bolts on each footer set in the concrete) , I have some steel I-beams that were gifted to me. The I-beams are massive - 20' long, top/bottom flanges are 6 3/4" wide (1/2" thick) with 1/4" center support and are 13 7/8" tall.

Fully loaded my bx2380 is around 4800lb (this is assuming fully loaded FEL, filled tires, mower deck, driver, fully loaded 3 point hitch). It's very possible I will be doing one of the two scenarios (1) pulling my log splitter across the bridge with a load of logs in FEL or (2) carrying material across bridge in bucket with rear ballast. As such, I'm wanting to support 5,000 lbs on the bridge at any given time.

The bridge will be cantilevered (21" on each side) with center of I-beams being about 46 3/4" apart. The 21" cantilever does not take into account any handrail, so the usable deck will be probably 7'6" or so so the cantilever will be 18" or so.

Next step is to work on the cross beams. Here's where I am seeking input, I'm no deck builder and haven't quite figured out the weight to cross beam spacing (similar to joists on a deck). Originally I was thinking I'll just get some 4x4s with 2 decking (vs 5/4 deck boards). I'm having reservations about the weight that the 4x4 can support, especially on the middle span between i-beams.

Anyone familiar enough with weight to cross beam spacing? All of the deck calculators i've seen take into account 50psf load or set a max span. Is 50psf enough for a tractor? would 4x4s side by side be enough? Should i consider 2x6, 2x8, 2x10 (single or double)? what spacing 12 oc? Is 5/4 decking enough? or should i go ahead and do 2x for the decking as well?

I'm sure I'll almost never drive with the wheels exactly on the beams (tractor, log splitter, side by side, 4 wheeler, etc).

All of the lumber I'll be using will be pressure treated.

Dan
 

fried1765

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Equipment
Kubota L48 TLB, Ford 1920 FEL, Ford 8N, SCAG Liberty Z, Gravely Pro.
Nov 14, 2019
6,455
4,093
113
Eastham, Ma
I have a creek that crosses the middle of my back yard and I'd like to get my BX2380 across it and due to cost, I'm building a bridge vs doing a culvert. After speaking to county engineering and fire marshall, I can build a bridge without permits (Just had to agree in wring the bridge will not be used for commercial traffic such as a rental, wedding venue, etc). If the bridge were to be used for anything but personal use, It would have to support the weight of county fire equipment and be permitted and engineered.

The bridge will be 8' wide (end to end, hand rail will take a way from the actual width) and 20' long (ramp on each end (far side bank is higher than near side)

So far, I have the 4 x 24" round footers (2 on each side of the creek) done using 5000psi concrete. Running across the creek (girders) between the footers (2 bolts on each footer set in the concrete) , I have some steel I-beams that were gifted to me. The I-beams are massive - 20' long, top/bottom flanges are 6 3/4" wide (1/2" thick) with 1/4" center support and are 13 7/8" tall.

Fully loaded my bx2380 is around 4800lb (this is assuming fully loaded FEL, filled tires, mower deck, driver, fully loaded 3 point hitch). It's very possible I will be doing one of the two scenarios (1) pulling my log splitter across the bridge with a load of logs in FEL or (2) carrying material across bridge in bucket with rear ballast. As such, I'm wanting to support 5,000 lbs on the bridge at any given time.

The bridge will be cantilevered (21" on each side) with center of I-beams being about 46 3/4" apart. The 21" cantilever does not take into account any handrail, so the usable deck will be probably 7'6" or so so the cantilever will be 18" or so.

Next step is to work on the cross beams. Here's where I am seeking input, I'm no deck builder and haven't quite figured out the weight to cross beam spacing (similar to joists on a deck). Originally I was thinking I'll just get some 4x4s with 2 decking (vs 5/4 deck boards). I'm having reservations about the weight that the 4x4 can support, especially on the middle span between i-beams.

Anyone familiar enough with weight to cross beam spacing? All of the deck calculators i've seen take into account 50psf load or set a max span. Is 50psf enough for a tractor? would 4x4s side by side be enough? Should i consider 2x6, 2x8, 2x10 (single or double)? what spacing 12 oc? Is 5/4 decking enough? or should i go ahead and do 2x for the decking as well?

I'm sure I'll almost never drive with the wheels exactly on the beams (tractor, log splitter, side by side, 4 wheeler, etc).

All of the lumber I'll be using will be pressure treated.

Dan
Please give us your definition of "cross beams".
Are you referring to cross stiffeners, (bridging) under the decking, to stabilize the steel beams?
If so, how would you attach them to the steel?
Or.....are you referring to the actual decking, as being "cross beams"?
Stiffeners (bridging) would be below deck level, and would not receive any weight from the tractor wheels.
 

dan_m

Active member

Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
Please give us your definition of "cross beams".
Are you referring to cross stiffeners, (bridging) under the decking, to stabilize the steel beams?
If so, how would you attach them to the steel?
Or.....are you referring to the actual decking, as being "cross beams"?
Stiffeners (bridging) would be below deck level, and would not receive any weight from the tractor wheels.
Cross beams to support the decking. On top of the i-beam.

Don't think i can just lay 5/4 decking or 2x on top across (perpendicular) the I-beams and expect it to support the weight. I was thinking of it as a deck.

The deck posts would be replaced by I-beams. Now i need to add joists then decking on top.

If that a bad way to think about this project?

Dan
 

mikester

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M59 TLB
Oct 21, 2017
3,143
1,625
113
Canada
www.divergentstuff.ca
Draw an elevation sketch and I will do your engineering work for you for free. I'll even stamp the drawings so I will take on the liability until I die.

While I'm at it I mind as well fabricate and install it for you for free.

Hint: If you knew what you were doing then you wouldn't be posting this question on an anonymous user group. Since you don't know or understand the problem please go hire a qualified engineer to do the design for you. I know it's expensive but that's the cost of living the lifestyle you want to have.

50psf design load for a bridge to drive vehicles over LMAO. Do yourself a favour stop being cheap and put in a culvert. If you went this route the job would be done by now.
 
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dan_m

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Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
Cross beams to support the decking. On top of the i-beam.

Don't think i can just lay 5/4 decking or 2x on top across (perpendicular) the I-beams and expect it to support the weight. I was thinking of it as a deck.

The deck posts would be replaced by I-beams. Now i need to add joists then decking on top.

If that a bad way to think about this project?

Dan
Here's a picture of the I-beams

Dan
 

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dan_m

Active member

Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
Draw an elevation sketch and I will do your engineering work for you for free. I'll even stamp the drawings so I will take on the liability until I die.

While I'm at it I mind as well fabricate and install it for you for free.

Hint: If you knew what you were doing then you wouldn't be posting this question on an anonymous user group. Since you don't know or understand the problem please go hire a qualified engineer to do the design for you. I know it's expensive but that's the cost of living the lifestyle you want to have.

50psf design load for a bridge to drive vehicles over LMAO. Do yourself a favour stop being cheap and put in a culvert. If you went this route the job would be done by now.
Sure, give me the 40,000 i was quoted for a culvert and I'll be glad to pay a professional to do it.

btw, lot next door had a house that was just completed. They paid 50,000 for their fire marshal approved / engineered culvert and got a discount because they heavy equipment was there already to clear the land and dig the basement to build the house.

Dan
 
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chim

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L4240HSTC with FEL, Ford 1210
Jan 19, 2013
1,758
844
113
Near Lancaster, PA, USA
If I understand the information you provided, you have parallel steel (tops of beams) that have an open space of 40" between them and they are 53-1/2" outside-to-outside. That sounds like your tractor could almost drive across on the beams. Absolutely not advisable but that would seem to indicate the deck may not need to be as heavy as would be needed with the beams set to the sides of the bridge and creating a 7' span between them.

I'd bet an engineer would have suggestions on bracing between the beams to avoid twisting.

I lack the training to give you an accurate answer. I do have hands-on, seat of the pants experience with over 50 years of making things. You'd be better off getting advice form a person who really has the ability to evaluate your plan. No guarantee the advice you glean from chat boards isn't coming from people who only THINK they are engineers. Anyone can make claims of expertise, like the fake doctors who did surgeries in real hospitals.
 
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fried1765

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Kubota L48 TLB, Ford 1920 FEL, Ford 8N, SCAG Liberty Z, Gravely Pro.
Nov 14, 2019
6,455
4,093
113
Eastham, Ma
Cross beams to support the decking. On top of the i-beam.

Don't think i can just lay 5/4 decking or 2x on top across (perpendicular) the I-beams and expect it to support the weight. I was thinking of it as a deck.

The deck posts would be replaced by I-beams. Now i need to add joists then decking on top.

If that a bad way to think about this project?

Dan
"the deck posts would be replaced by I -beams........????
"Now i need to add joists then decking on top".......????
Are you suggesting that your decking would be applied longitudinally?
 

dan_m

Active member

Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
If I understand the information you provided, you have parallel steel (tops of beams) that have an open space of 40" between them and they are 53-1/2" outside-to-outside. That sounds like your tractor could almost drive across on the beams. Absolutely not advisable but that would seem to indicate the deck may not need to be as heavy as would be needed with the beams set to the sides of the bridge and creating a 7' span between them.

I'd bet an engineer would have suggestions on bracing between the beams to avoid twisting.

I lack the training to give you an accurate answer. I do have hands-on, seat of the pants experience with over 50 years of making things. You'd be better off getting advice form a person who really has the ability to evaluate your plan. No guarantee the advice you glean from chat boards isn't coming from people who only THINK they are engineers. Anyone can make claims of expertise, like the fake doctors who did surgeries in real hospitals.
I understand. I've got a few decades of learning and doing myself.

I do plan on bracing the beams - that's the easy part and why I didn't mention that in original post. I'm more concerned about the top cross beams that will support the decking/loads. I'll probably weld in some angle iron or square tube between the i-beams for support. I guess I could weld it even with the top flange and add some additional structural support to help with the span between i-beams.

From what I recall (don't have numbers here with me right now), but the wheels of the tractor would not be sitting entirely on the beams and the wheels of a side-by-side would not be on either beam.

I did just find that 2 - 2x8 can support 4690lbs at 4' span ( 2-2x10 can support 5000lbs). That's a bit wider than my span. If I used more of them (6 or 8" vs 12 oc) that would help with weight distribution as well.

Thanks!

Dan
 

Tughill Tom

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Equipment
B3200
Dec 23, 2013
1,105
1,121
113
Turin, NY
Here's a picture of the I-beams

Dan
This is one I built with my Snowmobile Club. It's got 5- 14" power poles across the span about 35 ft. The decking is 2X12X14 Larch with we get from a local mill guy.
The runners stop wear from the Groomer drags tearing up the decking. The Groomers weight in 18,000LBS to 22,000 LBS without any flexing.
I did build on a 140 year old Railroad Tressel that had steel spanning the creek 40 ft long. We added a couple on power poles on it also. We bolted 2x8 on the steel with carriage bolts to be used as the nailer for the decking.
We do screw them with big lags/ construction screws
1686664440614.png
 
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dan_m

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BX2380
Jul 9, 2020
197
92
28
Georgia
"the deck posts would be replaced by I -beams........????
"Now i need to add joists then decking on top".......????
Are you suggesting that your decking would be applied longitudinally?
Not exactly.
Basically I'm thinking of building a cantilever deck.
Instead of sitting the deck (in a traditional sense) on vertical posts, the deck would be supported by the 2 I-beams.

example
I-beams (posts in deck) are N to S facing (perpendicular to creek).

Cross beams (joists) would be E to W facing ( parallel to creek) - what size and what spacing is the unknown. As of last post, probably 2-2x8 or 2-2x10.

The decking (what walk and drive on) would be N to S facing (perpendicular to creek). Probably 2x (2x8 or 2x10) isntead of 5/4 deck boards.


Dan
 
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dan_m

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Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
This is one I built with my Snowmobile Club. It's got 5- 14" power poles across the span about 35 ft. The decking is 2X12X14 Larch with we get from a local mill guy.
The runners stop wear from the Groomer drags tearing up the decking. The Groomers weight in 18,000LBS to 22,000 LBS without any flexing.
I did build on a 140 year old Railroad Tressel that had steel spanning the creek 40 ft long. We added a couple on power poles on it also. We bolted 2x8 on the steel with carriage bolts to be used as the nailer for the decking.
We do screw them with big lags/ construction screws
View attachment 104851
That's a cool bridge.

How does the decking hold up to the weather?

I did think about adding another layer of decking where wheels drive for runners, but think I like the look of having the entire deck be flat. Not far from where I live is an old bride that looks almost like that except it has rails on the sides.

I did find a local saw mill guy who can cut some white oak. Which I considered using for decking instead of pressure treated 2x. Never used white oak but know many trailer owners use it for decking.

Years ago when I was involved in TU, helped build a few pedestrian bridges across creeks. Mostly utility poles (larger spans) but one was from felled tree and all in conjunction with USFS and DNR. The USFS still uses old tools to move the logs by hand.

Dan
 
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Tughill Tom

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Equipment
B3200
Dec 23, 2013
1,105
1,121
113
Turin, NY
That's a cool bridge.

How does the decking hold up to the weather?

I did think about adding another layer of decking where wheels drive for runners, but think I like the look of having the entire deck be flat. Not far from where I live is an old bride that looks almost like that except it has rails on the sides.

I did find a local saw mill guy who can cut some white oak. Which I considered using for decking instead of pressure treated 2x. Never used white oak but know many trailer owners use it for decking.

Years ago when I was involved in TU, helped build a few pedestrian bridges across creeks. Mostly utility poles (larger spans) but one was from felled tree and all in conjunction with USFS and DNR. The USFS still uses old tools to move the logs by hand.

Dan
This one is 3 years old and we average 220 inch's of snow they hold up. It's the Sleds that tear them up with carbides and studded tracks.

White Oak would be great but it's heavy. The larch is lighter and cheaper which is a plus for us as sometimes we're building in the middle of a wet corn field and it get dicey getting materials in place.
The decking isn't dried when we install it, so it does shrink and drain water.

The Land owner where this one is drove his 30 ton excavator across it this year to install Drain Tiles in the field.

We didn't but rails on this one, we have one operator who is drawn to rails like their magnetic. He them tears out with the blade on the groomer and says "We don't need those F#$^** Things!
 
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dan_m

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BX2380
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Georgia
This one is 3 years old and we average 220 inch's of snow they hold up. It's the Sleds that tear them up with carbides and studded tracks.

White Oak would be great but it's heavy. The larch is lighter and cheaper which is a plus for us as sometimes we're building in the middle of a wet corn field and it get dicey getting materials in place.
The decking isn't dried when we install it, so it does shrink and drain water.

The Land owner where this one is drove his 30 ton excavator across it this year to install Drain Tiles in the field.

Down here in the south, Southern Yellow Pine is king! There's a bunch of hobby sawmills that's cheaper than lumber yards and box stores. Mostly the hobby sawmills deal with pine and oak. Some of them that market to woodworkers also deal with stuff like hickory, cedar and sweetgum. The most cost effective / durable for what I would need would be the white oak. Still not convinced I want to use that vs pressure treated 2x

Dan
 

fried1765

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Kubota L48 TLB, Ford 1920 FEL, Ford 8N, SCAG Liberty Z, Gravely Pro.
Nov 14, 2019
6,455
4,093
113
Eastham, Ma
Not exactly.
Basically I'm thinking of building a cantilever deck.
Instead of sitting the deck (in a traditional sense) on vertical posts, the deck would be supported by the 2 I-beams.

example
I-beams (posts in deck) are N to S facing (perpendicular to creek).

Cross beams (joists) would be E to W facing ( parallel to creek) - what size and what spacing is the unknown. As of last post, probably 2-2x8 or 2-2x10.

The decking (what walk and drive on) would be N to S facing (perpendicular to creek). Probably 2x (2x8 or 2x10) isntead of 5/4 deck boards.


Dan
I am at a loss as to why you would be needing "cross beams (joists)" unless you plan to run your decking longitudinally.
You should use bridging to keep the steel beams stable, and that could be cross beams, but would sit well below the decking, would not be loaded from above, and would not be considered to be a "joist".
I think we have a terminology issue here.
 
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lynnmor

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B2601-1
May 3, 2021
1,308
1,016
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Red Lion
I would price out white oak and if it isn't too costly throw it down and call it a day. Pressure treated today isn't your fathers pressure treated and it will rot like it was never treated.
 
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Alfred_2345

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L3901, LA525, BH77, SGC1060, RZ60, Box Blade, Z726XKW ZTM, RTV-X900
Jan 5, 2023
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53
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Northwest Arkansas
Have you considered used railroad ties as decking directly on the I-beams?
I know its a bit lat as you have done your piers already but if the I-beams were spaced at the width of the tractor tires, your decking wouldn't be 'carrying' the load. (Assuming you only plan on driving the tractor across.)
 
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rc51stierhoff

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B2650, MX6000, (BX sold)
Sep 13, 2021
1,953
2,148
113
Ohio
I have a creek that crosses the middle of my back yard and I'd like to get my BX2380 across it and due to cost, I'm building a bridge vs doing a culvert. After speaking to county engineering and fire marshall, I can build a bridge without permits (Just had to agree in wring the bridge will not be used for commercial traffic such as a rental, wedding venue, etc). If the bridge were to be used for anything but personal use, It would have to support the weight of county fire equipment and be permitted and engineered.

The bridge will be 8' wide (end to end, hand rail will take a way from the actual width) and 20' long (ramp on each end (far side bank is higher than near side)

So far, I have the 4 x 24" round footers (2 on each side of the creek) done using 5000psi concrete. Running across the creek (girders) between the footers (2 bolts on each footer set in the concrete) , I have some steel I-beams that were gifted to me. The I-beams are massive - 20' long, top/bottom flanges are 6 3/4" wide (1/2" thick) with 1/4" center support and are 13 7/8" tall.

Fully loaded my bx2380 is around 4800lb (this is assuming fully loaded FEL, filled tires, mower deck, driver, fully loaded 3 point hitch). It's very possible I will be doing one of the two scenarios (1) pulling my log splitter across the bridge with a load of logs in FEL or (2) carrying material across bridge in bucket with rear ballast. As such, I'm wanting to support 5,000 lbs on the bridge at any given time.

The bridge will be cantilevered (21" on each side) with center of I-beams being about 46 3/4" apart. The 21" cantilever does not take into account any handrail, so the usable deck will be probably 7'6" or so so the cantilever will be 18" or so.

Next step is to work on the cross beams. Here's where I am seeking input, I'm no deck builder and haven't quite figured out the weight to cross beam spacing (similar to joists on a deck). Originally I was thinking I'll just get some 4x4s with 2 decking (vs 5/4 deck boards). I'm having reservations about the weight that the 4x4 can support, especially on the middle span between i-beams.

Anyone familiar enough with weight to cross beam spacing? All of the deck calculators i've seen take into account 50psf load or set a max span. Is 50psf enough for a tractor? would 4x4s side by side be enough? Should i consider 2x6, 2x8, 2x10 (single or double)? what spacing 12 oc? Is 5/4 decking enough? or should i go ahead and do 2x for the decking as well?

I'm sure I'll almost never drive with the wheels exactly on the beams (tractor, log splitter, side by side, 4 wheeler, etc).

All of the lumber I'll be using will be pressure treated.

Dan
If there is any chance your machine could get stuck, have trouble and need recovered…now is time to consider the spec / load rating is enough for a recovery vehicle to get you unstuck should you have a problem.
 
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dan_m

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Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
I am at a loss as to why you would be needing "cross beams (joists)" unless you plan to run your decking longitudinally.
You should use bridging to keep the steel beams stable, and that could be cross beams, but would sit well below the decking, would not be loaded from above, and would not be considered to be a "joist".
I think we have a terminology issue here.

I understand what you're saying but can't envision it in my head.

Here's some quick sketches of what I have in mind.

looking at the bridge straight on, it would be like this:

1686675895591.png

8' width would be outside-to-outside of the hand rail - the usable width would be 8' - whatever width of handrails I decide.
Some of the cross beams would be 10' wide (maybe 12) so I can add an angled brace for stability of the hand rail.

Since the beams are I-beam, I planned on installing support between the 2 beams (between the top and bottom flanges and in the middle ) - i could add some at top and use for additional support for the cross beams (didn't think about that initially).

1686676105505.png


looking at the i-beams straight on, the blue line would be the brace (in reality more in center of the height of the i-beam)

looking down from above, the cross beams (as in joists of a deck) i'm referring to would be the green in this picture (blue being i-beams). I would not lay the 2x8 (or 2x10) on the long side, but the short side - that's where the strength comes from. There would be a gap between cross beams (that gap is yet to be determined (maybe 6", 8")

1686676171446.png


1686676862107.png

in the above image, the black is my i-beam spanning the creek
the 2x8 or 2x10 is the cross beam (aka joist) running perpendicular to the i-beams. It would be sitting like a joist does with the 1.5" side on top of the beam with height being either 7.25 for 2x8 or 9.25 (2x10) - ignore the typo of 9.24 :cool:


On top of the 2x8 or 2x10 would be the actual surface I would walk/drive on and it would run parallel to the i-beam.


Are you suggesting I lay the 2x8 or 2x10 down on the long side and use that as the decking (surface I walk/drive on)?

In my research I didn't find that laying the 2x down would support the weight I needed, especially with the span between the beams.

Dan
 

dan_m

Active member

Equipment
BX2380
Jul 9, 2020
197
92
28
Georgia
If there is any chance your machine could get stuck, have trouble and need recovered…now is time to consider the spec / load rating is enough for a recovery vehicle to get you unstuck should you have a problem.
Little to none.

Currently the far side only has a shed and some firewood drying on some pallets.
Currently the previous owner built a pedestrian bridge across the creek (it's old and needs to be replaced).

After completing the bridge, I'm going to clear a few small paths and probably throw down some gravel on them.
Then I'm going build a couple simple lean-to/car port type structures for drying/storing firewood and to cover my FEL when not on tractor, ballast box, log splitter, dump carts, mower, etc.

Dan