# Wood Recommendation for Bridge



## Tom Parkins (Jan 2, 2008)

I am in the process of replacing a wooden truss bridge and I intend to replace it with another wooden truss. The bridge will nominally span 4 feet and will be a single track through pony truss design (Pratt or Warren). 

I have some 1 x4 Red Oak and 1 x 4 Cedar. The cedar has many more knots. The oak is nearly clear of knots. This bridge will be out year round in northern Delaware with snow and ice in winter and shaded sun in summer. The oak seems stronger and is definitely heavier. The cedar is lighter, rougher. I am willing to stain or paint it. 


_*Which wood do you recommend?*_

I intend to use brad nails and Tightbond II for holding the trusses to the chords. Top/bottom chords are nominally 1/2" x 3/4" Trusses are 1/2 x 1/2. 


_*Recommendations on fastening trusses to upper and lower chords?*_

Thanks in advance. Tom


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## Russell Miller (Jan 3, 2008)

Good Cedar is more rot resistant than Oak. Oak also tends to expand and contract more. You are going to put a lot of effort into building the bridge so use the best wood you can find. I used recycled old growth Heart Redwood on my trestle and bridges and used Titebond III and Black E-6000 for glue.


















Russ


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## Dean Whipple (Jan 2, 2008)

I used regular redwood, use old growth if you can find it I although I live in a milder climate my bridge has been outside about 10 years.
Do not use Tightbond II it is not waterproof use Tightbond III.
I would also recommend using a pin nailer instead of a brad nailer because it will not be as apt to split the wood. Harbor Freight has them for about $30.00 I used my HF nailer when I repaired my bridge.

You should use a wood preservative I treated the redwood using a copper brown wood preservative, the preservative had worked very well for the 6 or 7 plus years that bridge had been outside, several years ago I brought it inside did some TLC to it and only had to replace one of the small support pieces painted it with "Copper-Green" brown wood preservative which I bought at Home Depot*http://www.mylargescale.com/Communi...en-brown-wood-preservative-gallon-209444.html* and figure it's good for another 6 or 7 years.....


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## Richard Weatherby (Jan 3, 2008)

Tom; 
I am in northern Maryland, not far from northern Delaware. Click on my signature link to see my bridges and trestles. I think it depends on whether it is red oak or white oak. It think white oak is more resistant than red oak. It think it is the other way with cedar, although I may be wrong. I always thought red cedar is more resistant, although there is white cedar shingles coming out of the northeast. My original arched tresltles and bridges were may from Trex, but I quit doing that. Trex is not meant to be ripped into smaller pieces and thus exposes the half saw dust & half plastic. The saw dust gets wet and small pieces (1/8" thick) warp. I then switched to pressure treated lumber (cut outdoors!!). The treated lumber seems to be working OK. However, the next ones will be redwood, which I hauled from the west coast one year. I don't know where you can get it here the east. Those west coast guys are just lucky that their HomeDepot sellls redwood like ours sells oak. I have built a major building with stained cedar and it has held up very well.


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## denray (Jan 5, 2008)

Dick 
You are right white oak will hold up a lot better than Red Oak, also if it has not been through the kiln, but air dried while stripped with small strips to allow air to circulate, 
Air dried will hold up a lot longer than kiln dried. 
Dennis


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## Jerry Barnes (Jan 2, 2008)

With all the work involved you want to make sure you use redwood or cedar and Titebond III glue. Been quite a few stories on here of nice bridges falling apart.


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## jimtyp (Jan 2, 2008)

I also recommend Redwood and Cedar. I also recommend titebond III and a 23 gauge pin nailer. Glue and nail as many wood parts together as you can before staining - makes the staining (if you decide to stain) harder, but your end product will hold up for many decades. I find that oak tends to warp a bit. I did some research on wood types a while back. I compared expansion/contraction, moisture content and warping tendencies. Check out this link for outdoor structures, it has some good info -  wood for outdoor structures.


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## SD90WLMT (Feb 16, 2010)

As Jerry pointed out, many nice bridges have fallen apart!! I read about a guy that wrote one of those "If only I had known" articles for GR some years back. He glued the wood parts - "after staining the individual parts" and the bridge fell apart in a pile of pieces!!! The note here is that glues DO NOT Stick to stains - at all... 

Good luck with your 1st bridge!! 

Dirk - DMS Ry.


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