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Est. 1998 — 27 years of woodworking knowledge

REAL MILK PAINT

Adding the Bridge Rails

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Adding the Bridge Rails

#1

Adding the Bridge Rails

Bill Tindall, E.Tn.

Installing rail



Rail is cut to exactly 12 feet with a jig and chop saw. Many rails are cut at one time. They are carted to the location they go on the bridge. The cart with rails and the cart with tools move down the bridge as the rail gets installed. There is little manual moving of the lumber, a great time saver.

The top rail is installed first. The top of the posts will be spaced exactly four feet if the angle brackets are spaced four feet. A 100’ tape measure is stretched across the post tops and the tops are adjusted to align at four foot increments, a procedure much faster than using a level. A line is pulled across the posts to locate the bottom of the top rail.



Minor variance in post height is compensated for by variance in the amount the top rail projects above the post top. When cutting posts if the “left over” was up to ¼” short for some position we used it anyway. Aligning the top rail with the line ensures the top of the rail will be straight across the bridge.



Rail is hoisted into position and tacked in place with a finish nailer.



Screw locations are located by punching a drill through a template. PIC. Someone then comes along and drives in the Powerlags. No predrilling is necessary.

Once the top rail is on the through bolts are installed to secure the post.


A spacer block is used to measure 3 7/8” from the bottom of the top rail. These marks are used to align the next rail. Repeat down the bridge. The rails that finish the bridge are not likely to be exactly a 4’ increment. They are cut to length from measurement of the remaining distance.

Compared to the first bridge built we take advantage of huge labor saving designs, materials and procedures. The large number of parts and fasteners means that a small savings on any step translates to significant savings on the bridge. Some of the savings were way more than small.



Spax Powerlags are available in shank diameters that satisfied the engineer that had to approve every detail of the bridge. Conventional lags must be countersunk, and employ a through hole through the rail and a pilot hole in the post, then a 4th tool to drive in the lag. That’s 4 drills, cords and a generator to drag around the bridge. Powerlags saved drilling 15,000 lag screw holes in this bridge!

The post attachment hardware, previously described, was both less expensive material and vastly quicker and safer to install.

Accurate lay out enabled the about 225 rails, to be pre- cut to 12’ using a stop block and chop saw.

An unanticipated bonus, compared to the 2 x 8 previously used the 2 x6 was much easier to install. The pieces were 25% lighter, not insignificant when talking about soggy treated lumber. They are more flexible, enabling them to be straightened as they were tacked in place with the nailer. Permanent screwing with the Powerlags could then be done at convenience. Any time someone in the crew was not occupied they drove in Powerlag screws, 5000 for the long bridge over the river.

Re: Adding the Bridge Rails

#2

Re: Adding the Bridge Rails

Keith L Newton

Looks good Bill,,,,,,,, mostly. I've been using another brand of those screws, Timberlock is the brand Lows carries. I know it will do no good to argue against the engineered method, but sandwiching those 2x8s flat between the ties and deck still makes me shutter. That is the worse thing you could do to accelerate rot.

Also, putting all your earlier lags, and now screws in a straight plumb line, ratter than offsetting back and forth reduces the wedging effect of the combined 10 of them along the same line of grain.

I'm not sure tearing out rotten decks to observe what might have caused premature decay is a chapter in engineering school.

Re: Adding the Bridge Rails

#3

Re: Adding the Bridge Rails

Bill Tindall, E.Tn.

sandwiching those 2x8s flat between the ties and deck still makes me shutter. what do you suggest as the alternative? I was able to reduce the size to six inch so as to dry quicker and incorporate a larger gap in the deck boards. I don't see any other way to deck a bridge.

The screws in a line have not been a problem on bridge rail.

The shanks of the Spax screws are larger diameter than Timberloc. And we get them from the factory at a third the cost at Lowes.

Re: Adding the Bridge Rails

#4

Trestle Bridges

Bill Tindall, E.Tn.


Shown is a picture of a typical trestle structure. 12 x 12's are joined together in numerous places, including in the water, with 12 x 12 surface contact. This bridge was built 100 years ago. Joining wood surfaces is unavoidable. As far as I know, with no alternative in construction, one compensates with treatment. The lumber we are using is treated to a 2X higher treatment level than anything you could have ever used, and 4X higher than typical deck lumber. It is expected to last decades in the ground.

That said, one objective in posting this adventure is to seek better ways of building these bridges. We have 11 more to do.

Re: Adding the Bridge Rails

#5

Re: Adding the Bridge Rails

Ralph Lipeles

I would have preferred vertical rails to prevent youngsters from climbing up and over.

Re: Adding the Bridge Rails

#6

Me too

Bill Tindall, E.Tn.

I would have preferred vertical rails for visibility. Young children climbing is not much of an issue on these trail bridges. "Experience has shown that vandals kick out 1 1/2 x 1 1/2 vertical rails"......I was told as justification for rejecting this rail style. And that was the end of that suggestion.

Re: Adding the Bridge Rails

#7

Re: Me too

William Duffield

Aren't there also more serious safety issues with vertical rails on bridges intended for bicycles? If a bike rider collides with a vertical rail (front tire, handle bar, foot or pedal) I would think it much more likely than horizontal rails to result in a sudden stop and spill.

Re: Adding the Bridge Rails

#8

good point

Bill Tindall, E.Tn.


This new bike/hike bridge in Kingsport Greenbelt provides for an open view but I would rather crash into my rail. It is a new, not a converted RR bridge.

Some picket rails have a guard rail. What you point out demonstrates the many factors that are balanced when deciding a rail style.

Re: Adding the Bridge Rails

#9

Re: Adding the Bridge Rails

Keith L Newton

Well, it seems to me that the railroad ties are superfluous so I would not use them. I don't know what was under them, due to the wide flashing, but I suspect is more massive timbers that are actually structural. I like seeing that flashing. Then above that, I would rip some 1x 6" decking in half to 2.75" that run across side to side, and their purpose is just to raise your joist off the flashing to allow good draining off the flashing. Also since one joist would be flush with both sides of the flashing otherwise forming a dam.

I'm assuming that the width of the top of the trestle is wide enough for the bike path. But first thing I would put up would be the post, once the jacklines were installed for the safety harneses. The post could be pre-drilled, with the Spax screws already driven up to just before coming out. A little temporary block could be screwed on to rest upon to index the height while a worker reached down to screw them on the outside of the beam below that flashing. Then the joist could be set on top of the 1 x 6 strips then screwed into the post sides. Toward the middle, short stakes could be screwed onto the trestle to hold the second joist upright. A short drop-girder fastened between the beams would support the middle joist. Without looking, I think maybe 2x4 joist meet code for a 4' span if you used one across between the post, although I'd probably use 2x6s.

Everything would drain good and last much longer with no flat faces either horizontal or vertical, other than where the post bolt on beside the trestle, and the railing above. Those might stay healthier longer with a bead of caulk along the top edge after they dry on down. Forget that curb / leaf catcher, I'd let the deck overhang the outside joist 1.5" if that doesn't call for a lot of wasted lumber to get the added 3" of length.

Re: Adding the Bridge Rails

#10

Re: Adding the Bridge Rails

Bill Tindall, E.Tn.

it seems to me that the railroad ties are superfluous We agree on that point. As the engineer I hired put it, you could stretch canvas over the massive stringers and have the same load rating on the bridge for a truck, Bob Cat or excavator crossing it. (we have to enable construction machinery to cross the bridges) The ties simply add the look of a RR bridge, but the firm designing the bridge doesn't agree. Sigh.

An alternative is to simply deck across the stringers (massive 16" deep by 26" wide beams that run parallel to tracks and sit on trestles). Most National Forest bridges are built this way. Labor is less but lumber cost turns out to be substantially more when 3 x 6 decking is used. (We built Bridge 1 this way) Our used ties are almost free, and with latest installation technique we can add ties and runners on a typical bridge with 3 man days labor. I have run the costs and Ties, runners and deck is substantially cheaper than 3 x6 deck over stringers.

Your design rests on the assumption that rot between 2x6" runners and deck is the limiting factor in deck life. High Bridge State Park is replacing a deck built with runners over ties. I will ask what the rot situation is for this area of the deck. I think the deck surface degradation necessitated replacement, but I will confirm.

so I would not use them. I don't know what was under them, due to the wide flashing, but I suspect is more massive timbers that are actually structural.

Re: Adding the Bridge Rails

#11

Re: Adding the Bridge Rails

Keith L Newton

Bill I understand what your up against dealing with the designers and others. I also know that as long as I've been reading your post that you are persistent. I think you ought to keep beating them over the head with the fact that it isn't all about the structural integrity and RR look, but the durability should be a top priority.

"High Bridge State Park is replacing a deck built with runners over ties. I will ask what the rot situation is for this area of the deck. I think the deck surface degradation necessitated replacement, but I will confirm."

That sounds good, but I hope they have someone who really inspects it rather than just sending in grunts to tear it all out. I know you are using better treatment than I can buy, but I doubt even that actually permeates the heartwood, which will be the first thing to rot. Once that shows, even though the part that took up the treatment chemicals is still good for another 30 years, it's like the adage of the weakest link of the chain.

I hope that you don't take my post as anything other than trying to be helpful. I really admire what you and Mrs Tindall are doing to contribute to this monumental endeavor. Congrats

Re: Adding the Bridge Rails

#12

A treatment surprise

Bill Tindall, E.Tn.

In fact, the treatment does penetrate to the center of 2X lumber. One can see the copper deposited in the pores and sometimes when driving a screw I have seen treatment liquid squirt out of the center of a piece.

The pine is plantation grown. It does not have heartwood. It will someday, but not in the growth cycle commonly practiced.

What I didn't tolerate is pith. Some deck pieces are cut from the center of the tree and hence have pith down the center of the 2 x 6. I rejected these pieces. I have seen that pith does not hold up on a deck (examining other bridges). I sorted and inspected all the lumber before it got installed. Clear pieces went for the top rail and other show areas. The "Select" packs of 2 x 6 had many pieces clear at least on one face. Bark edges went on the bottom rail. Worst sides went out. The best of the worst sides faced the suspension bridge parallel to the RR bridge. People will look at the bridge from this side. Etc.

The only influence I have came and went with funding the large bridge. What I was able to change did in fact carry over to the next 2 bridges. Now 5 State funded bridges are up for bid and I have nothing to do with the process. Realistically any influence I have has ended.

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