Redecking bridge

[tlj87]

My 50' long, 3-ton rated foot bridge needs to be re decked this year. Right now it is decked 5' wide (also the width of the I beams center to center). I am considering using tongue and groove 2x6 lumber instead of the regular 2x8s that are on it now. The problem I have with the standard lumber is that is bows and curls with time. It is in direct sunlight most of the day. I am thinking TG lumber might look good and provide a nice smooth surface. Thoughts? thanks

 

[Rock knocker]

T&G is not available pressure treated. It will also not drain and provide a surface likely to get slick with mold, moss and algae.

 

[tlj87]

T&G is not available pressure treated. It will also not drain and provide a surface likely to get slick with mold, moss and algae.

The lumber yard quoted me 14.99 for a 2x6x16 pressure treated tongue and groove board.

 

[Rock knocker]

The lumber yard quoted me 14.99 for a 2x6x16 pressure treated tongue and groove board.

Ok, that's something I've never seen on the west coast.

It will hold water more and could be more likely to freeze into a dangerous sheet.

But if you can get PT T&G, the majority of my concerns would be alleviated. Even though your bridge is probably made of stout structural S or W sizes, I would also protect the steel from the chemically erosive pressure treated wood with some sort of isolator material. Roofing felt or Grace I&W Shield is commonly used. I would stay away from felt for your application, but you could also use very heavy visqueen, rubber or pvc roofing or the such.

 

[/pine]

I've seen a few spans planked with (full) 2" black locust boards that were "clipped" between the support beams...the clips were made from steel channel that resembled the clips commonly used on plywood roof sheathing... and left a defined space between the planks...FWIW...

 

[rd_macgregor]

I built a 40' x 6' wooden bridge/causeway on pilings across a small floodplain over ten years ago. The 2x6 PT deck boards are spaced about 3/8" apart for drainage and have held up well without appreciable cupping, bowing or warping. However, it is in a mostly shady and damp location and can be slippery at times, eg wet weather (and, of course, especially now that it is ice-covered!!).
Bob

 

[tlj87]

Even though your bridge is probably made of stout structural S or W sizes, I would also protect the steel from the chemically erosive pressure treated wood with some sort of isolator material. Roofing felt or Grace I&W Shield is commonly used. I would stay away from felt for your application, but you could also use very heavy visqueen, rubber or pvc roofing or the such.

Based on my measurements the beams are W12x50 braced with tubes welded between every 10 feet. All of the steel is painted. Should this barrier be continuous under the bridge deck?

 

[Rock knocker]

I would just put it on the top of the individual I-beams, with a space on either side for draining and ventilation.

 

[tlj87]

If I go with T&G, I can only get 16'ers, I am thinking of decking it 8' wide, up from 5'. This would allow me to take the RTV or BX with mower across the bridge with clearance on the side. I am thinking of lagging the decking to a 4x6 curb on the sides and screwing the decking into 2x8s which are bolted directly on top of the I beams, acting as the "tack strip". That leaves 1.5' on each side beyond the I beams. Bad idea?

 

[KennyG]

I would not go with T&G on anything that isn't covered. I want the water to drain as rapidly as possible. I've always used 2x, spaced and screwed down at 24" spacing or less and I don't see significant bowing.

The T&G you describe sounds to me like pole barn grade board. Is it ground contact treated?