Wringing cost from the Trail bridges

Tough exercise

Henry (Raleigh NC)

Bill - without knowing (or researching) the costs of various parts, that's a tough exercise. Smaller (beams, bolts, etc) presumably means cheaper - but aside from that I can't answer your question. Hard to start without knowing the costly items in the list - and how labor costs are to be figured in.

I look forward to seeing ideas, and what you actually did.

Henry

Re: Wringing cost from the Trail bridges

Mark Hennebury

I would go this route I think.

Re: Wringing cost from the Trail bridges

David Weaver

Mark's thought was my initial thought, too. But I have no idea what's required by code. The metal brackets seem avoidable, but some alternative solutions without them or without some of the fasteners would involve grooves or mortises - not sure if that's actually cheaper or would meet code (certainly cheaper if you don't count anyone's time).

codes are simple

Bill Tindall, E.Tn.

same code as residential deck. Basically we are building a residential deck on a bridge.

Since you ask, here is my 2¢

Keith L Newton

First off, let me just state, the structural part is not what you need to worry about, but, DECAY is the enemy of all your efforts and expenses. One of the things that I try to avoid, having torn down plenty of rotten decks and docks is to never have the broad faces of the lumber together where it can hold water and all the grunge that will wash in after it rains, then holds water along with pollen, decaying leaves, dirt and spores. Even the best pressure treatment doesn't permeate the resin rich cells of heart pine, so that will be the first place where the decay will get started. Once someone starts seeing mushrooms growing out of there, folks get jittery and the whole thing comes down.

I think you have gone way overkill on what was needed. Instead of 6x6" joist, 2x8 would have been my choice, even though 2x6 might have met code, but I don't know what the span is to check it. Then earlier did I see 2x6's flat, on top of the 6x6's that the deck is screwed down to? that is two layers of flat faces together destined to hold water. Then I'm not sure what the curb board is supposed to do, but that will provide another trap for water and debris.

As for all the bolts, have you taken a look at Timberlock screws? They will drive even without a pilot hole, although I always do when near the ends of boards, or when going really long. They are coated and of harder steel than lags, and the heads wouldn't need countersinking. https://www.lowes.com/pd/FastenMaster-0-x-2-7-8-in-Black-Ecoat-Flat-Head-Interior-Exterior-Structural-Wood-Screws-50-Count/3295058

I don't know if it was necessary to run the deck boards across rather than longitudinal, which probably would make steering less risky when individual boards cupped. So to get rid of the 6x6, with 2x6 flat, I would start with 2x10 drop girders running across maybe on 6' centers, with 2x6x12' joist on 16" centers running longitudinal, then decked with the standard 5/4x6 decking running across. If the drop girders are run long enough, the post for the rail could then run down to the bottom, and be fastened on beside it, as well as through the joist. I'll assure you that would be stronger than using those metal brackets.

I like to use 4x4 post, with 2x6 cap rail which has a top bevel on both sides leaving about 2" flat in the middle like a roof, as well as cut a little 1/4" groove back 5/16 from the edge, so all the water drips off out there rather than ever getting to under the cap. This also prevents the inevitable cup caused by the Sun drying the top out faster than the moisture comes out from the ever enlarging checks on the top face or just leaving it flat.

I would also drop those other 4 2x6s of the railing down to 5/4 x 6" and leave the curb off the deck so all the stuff which settles out of the air can just wash on off the ends of the 1-1/2" overhang from the last joist.

I hope you can follow this, and let me know if you have questions.

Re: Since you ask, here is my 2¢

Bill Tindall, E.Tn.

First off, let me just state, the structural part is not what you need to worry about This bridge has to meet structural codes.

One of the things that I try to avoid,is to never have the broad faces of the lumber together not possible to avoid.

Even the best pressure treatment doesn't permeate the resin rich cells of heart pine, Indeed true and the decay we see on the 100+year old timbers is decay of the timber centers before it was learned how to creosote treat these centers.

One of the changes I have made on the new bridges is to treat to UC4B or CCA as allowed. Treated lumber is plantation grown SYP that has no resin centers.

I think you (not me) have gone way overkill on what was needed. DUH!!! The original design seems ready to accommodate passenger trains. Those are 8 x 8 not 6 x 6. And it doesn't matter. They could be 1 x 1" as no vehicle can cross the bridge without tires directly over 26 x 16" stringers. There is no tension load on the deck. The through bolt yields at 76,000 pounds.

Then I'm not sure what the curb board is supposed to do,

Essential to hold the ties in place and provide a place to secure the posts.

have you taken a look at Timberlock screws? I'll deal with rails later

They will drive even without a pilot hole, although I always do when near the ends of boards, Found it unnecessary to use a pilot either at rail ends or even with driving 8" into an oak tie. They are amazing

I don't know if it was necessary to run the deck boards across rather than longitudinal You must not bike across timber bridges. It's essential to run deck boards perpendicular to bike travel.

then decked with the standard 5/4x6 decking running across. 5/4 decking does not last on trail bridges. It is not uncommon to use 3 x 6.

I like to use 4x4 post, Won't meet 200 pound code, especially so after a few years of weathering. Trail bridges are expected to last 40-50 years. Bridge rails are higher than residential rails, putting more force on post at attachment. The 200 pound code force multiplies by the height of the rail. 4 x 6 dry straighter. And the 5 1/2" span makes joining rail end joints easier. With a post spacing of 4', post cost is not an opportunity to save much by going to 4 x 4.

I would also drop those other 4 2x6s of the railing down to 5/4 x 6" I chose not to fight this battle. I have never seen a trail bridge with a 5/4 rail so there must be some reason to avoid it. Probably the reason to use 2" is for longer serviceable life. These bridges are 80% labor and 20% material cost.

I'll deal with other rail issues later.

....costs are 80% labor ...

Henry (Raleigh NC)

That detail was missing in the original question - and so really the Q is how to save labor.

Does not change anything but detail would have been helpful to know

Henry

My first thoughts...

David Weaver

..since you were mentioning the materials was to lighten the load on the posts and fasteners, and perhaps brace smaller posts and reduce fasteners, especially on the facing boards, and eliminate the angle plate by fastening the posts to the tie sides.

But if 80% of the cost is labor, it's a matter of eliminating materials that cause labor, or trading materials to some with less labor.

i've never built a deck, so don't know what's suitable, but my first choice would be smaller bolts and perhaps two cheap plates bolting 2x4s or 2x6s sideways to the ties and the rails bolted straight to them.

I haven't been following the number of ties, but fewer ties if they're more dense than they need to be for people and light maintenance vehicles (build the floor more like a wagon bed)

stay tuned.....

Bill Tindall, E.Tn.

....for the discussion of ties, or not ties, to be discussed next. Following ties will be the complicated discussion of rails and the conflict between rail codes and bikers experience when using the bridge.

Re: My first thoughts...

Bill Tindall, E.Tn.

But if 80% of the cost is labor, it's a matter of eliminating materials that cause labor, or trading materials to some with less labor.

As you will see in subsequent posts this was the route that yielded the most savings. In fact lumber cost is such a small portion of the cost we are going to buy a higher grade for future bridges and suffer less cull lumber we can't use for deck and rail.

Bridge estimates before I showed up were about $650 per foot for the deck and rail. Currently we have lumber down to $46/foot and hardware $15. Don't have a good figure on labor yet but it will be less than $200.

They are lucky they have ...

David Weaver

..someone involved who is too bored just doing the work to resist solving problems at the same time. Whether they know it or not!

Tons of costly and labor intensive work without much changing is what I'd refer to the "curse of the conscientious".