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Discussion Starter #1
I am building some trestles out of cedar fence boards and they are sitting in the dirt about 2". What is the best way to protect the wood from rotting. Is a stain enough?

Thanks,
Eroc
 

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Eroc

You didnt say if the wood pieces in the dirt were load bearing or if set on footings or where you are located.

Generally speaking wood in small cross section will not survive long in contact with soil and the decay is hastened if the soil is wet. Cedar has some natural protection from rot but it is not enough to give longevity untreated. The wood in contact with the ground must be well coated with a preservative - check your local codes for what is allowed. The most effective preservatives are either creosote or copper based products but these are highly toxic and not generally permitted. Stain definitely is inadequate.

Regards ... Doug
 

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Cedar in the soil will rot out in a few years. I would construct bases of stone or pressure treated wood for you cedar bents to sit on.

-Brian
 

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Discussion Starter #4
These are small trestles about 4 feet long. They are not set on footings, and maybe that is what I should do instead of putting them straight into the ground. I am not sure what you you mean about load bearing, the only load is the trains and the track. The wood is 3/4" by 3/4". Are there better ways to secure the trestle into the ground?

Thanks for the reply,
Eroc
 

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I use cedar and redwood for trestle bents and they were in ground for seven years then pulled out and moved and reinstalled and there was no rot. They have been in ground for another three years. Soil is clay and we don't get much rain.
 

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I placed my trestle in a trench I dug, little deeper and wider then the bents.
After I leveled it and had it in place I filled the trench with pea gravel and tamp it. I took it out after 18 years and it was good as new.
 

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If you water you plants, wood in the ground tends to be short lived. All of my trestle bents either sit on cement blocks placed on edge or on double bull nosed pavers used in decking and masonry work.
Once you've invested the time and effort to make a nice trestle, why watch it rot out in the dirt or water?
 

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I agree that ANY wood in contact with the ground should be protected. However, I would protect the entire structure, not just the parts in the ground. By treating the entire structure with some sort of preservative, you will avoid any moisture wicking down through the wood from the top, when it rains for instance. My theory is that by prtecting the bottom only you are creating a sort of bathtub for water to sit in.

One of the better woods for outdoor use is mahogany. There are several grades. Some inexpensive, while some are very expensive. But look at it this way. If you purchase a piece of IPE' for example, a very hard and durable form of mahogany, the amount of 3/4" square boards you can cut it into to build a trestle will make up for the cost of the material.

I have been using a mixture of boiled linseed oil and turpentine to treat my outdoor wood. Whether it's something in my garden railway or wheelbarrow handles. I even use it on the unpainted metal parts of outdoor tools, as it is a good rust preventative. And bets of all, it's a natural product, not a chemical. Use about 2/3 linseed oil and 1/3 turpentine. This way you can brush it on easily. The turpentine thins the oil and allows it to penetrate better.
 

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Posted By Ron Senek on 07/31/2008 6:18 PM
I use cedar and redwood for trestle bents and they were in ground for seven years then pulled out and moved and reinstalled and there was no rot. They have been in ground for another three years. Soil is clay and we don't get much rain.




and we don't get much rain.... that's the ticket. Dry cedar will last a good long time. Eroc is in LaLa Land and they don't get much rain either so he might be okay. I made a bunch of large tomato cages a few years ago out of 3/4" x 1 1/2" cedar (actual dimensions). They were used in raised garden beds (so decent drainage) but after 3 years not much was left of the underground portion.

-Brian
 

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Home Depot has a product called "Jasco Termin-8". It has copper naphthenate, which I believe is the same stuff they use in pressure treated lumber. It is the only product I found that specifically states for "in-ground" use. I've had stuff in the ground for 8 years and no problems so far. We don't get much rain in Vegas, but we have bugs. Seems to work against them.

Bob
 

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Discussion Starter #11
It does not rain here much but I am going to have a lot of vegetation that will need to be watered. So it sound like my best bet is to keep the wood from touching dirt and protecting the whole bridge from the elemnets.

toddalin I really like your soultion. I am also going to have to go across a water feature. Where did you get those pavers?

Madman where did you find the lower grades of mahogony?

Thanks everyone for your replies, it's been very helpful and please post more pictures.
 

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I got them at a local rock/masonry store in Tustin tha tis no longer in business. But lots of places have them (especially in teh Irwindale area). Let your finger do the walking. You are looking for "double bull-nosed bricks. These have been fired with a ceramic glaze so the water does not wick up them to the wood.

I'm in Orange County above Tustin and if you would like to come by and take a look, you are certainly welcome.
 

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Posted By ErocFx on 07/31/2008 10:41 PM
It does not rain here much but I am going to have a lot of vegetation that will need to be watered. So it sound like my best bet is to keep the wood from touching dirt and protecting the whole bridge from the elemnets.
toddalin I really like your soultion. I am also going to have to go across a water feature. Where did you get those pavers?
Madman where did you find the lower grades of mahogony?
Thanks everyone for your replies, it's been very helpful and please post more pictures.








The lumber yards sell 5/4" x 6" ( nominal dimensions ) mahogany decking boards. They look like they are a step or two above Phillipine Mahogany. I recently used some to re[lace some exterior window sills. It's very clear and nice to work with. I don't think you will find this material at Home Depot or Lowes. Try a better lumber yard. One that caters to the building trades.
 

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Posted By Trains on 08/01/2008 5:27 AM
Maybe try making it out of a hard wood and adding some protection?




Hard woods do not hold up well in the weather. Even when treated. Better materials would be Mahogany, Douglas Fir, Cypress, just to name three. Almost all wood that is buried partially in the ground will deteriorate at some point. The soft woods do better than the hard woods. But not all soft woods will perform equally well. Wood that is submerged entirely under water will last indefinately.

Oddly, railroads used Oak ties, a hard wood. But on a properly maintained right of way, the ties are never sitting in standing water or touching earth. Still, the railroads treated them with creasote to protect them from absorbing water from rain, spills from a train, etc. If you placed a piece of untreated Oak in or on the ground, it would be in very sad shape in just a few short years.
 

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I have used teak for most of my outdoor timber projects, and I treat this two or three times each year with a spray mixture of teak oil (basically thinned linseed oil) and a wood preserver we get here called Cuprinol. I also avoid bedding timber in the ground. I adopted a method of bedding short lengths of brass angle in concrete and then bolting the timber uprights to the brass just above soil level. The area is then covered with a thin layer of gravel to hide the brass.

Across the pond the timber stands on cast concrete foundations.

I have one bridge made of softwood that has been in service now for about 11 or 12 years. It is also mounted on brass angle in concrete pads and whilst it is showing some signs of age - splitting on some lengths - it is still structurally sound. This has also been treated once or twice each year with a Cuprinol wood preserver.
David
 

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Cuprinol and many other copper based wood preservatives are very effective ... but they are also highly toxic. They have been banned for environmental reasons in a great many jurisdictions leaving many of us with less effective alternatives.

Regards ... Doug
 

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Eroc
I have a 30 foot long x 42" tall trestle, under my whole trestle is cement to prevent unwanted weeds, I installed angle iron strips about 4 inches long in the cement and about 2" up at the leg of a bent, then I clamped the two together with a hose clamp, makes it very solid and my lumber is not in the cement, My trestle is a hardwood, and I know from lots of building experience wood in cement will rot quickly, wood that has the bottom in dirt and then cement poured around the post will last almost indefinately. So my bents are just above the cement, with gravel on the cement you can't see the bottom of the bents.
Dennis
 

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David has said what most people don't want to hear. He treats his wood two or three times per year. I like the idea of teak oil. I havn't seen or heard of Cuprinol being used for quite some time. There used to be another brand by the name of Koppers, I believe I have the spelling correct, that made wood almost indestructable. God knows what chemicals that was made up of.
 
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the best wood for bases i know is "palo santo"/palisander.
we use it for fencing down here.
very oily and good for fifty years in the earth.
 
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