I am going to raise my new layout, i have a lot of trex I used on the last one and will use that to lay on top, my question is how close do I have to keep my PT lumber before it will warp, I only have sun half the day in the morning, the PT lumber will be the base and raised on cement blocks, kind of laying a ladder down and running the trex on top of that, so like the ladder rungs are spaced a certian length how far apart should I space the 2 x 4`s apart to keep the lumber from twisting.
Tom H
Tom,
You won’t keep the PT from warping no matter what you do. The best that can be done is keeping the warpage to a minimum.
Getting kiln dried PT that is straight would be a great start but of course the first wet/dry cycle takes care of that.
Getting wet/green pt and getting it cut, braced, and screwed together before it can dry is about the best you can hope to achieve. This will keep the twisting to a minimum.
I would think 24 inch or 16 inch centers would be good depending on your table width. I use 12 inch centers on my tables but I don’t use any decking. I would think about the span of the trex as it sags pretty easily if not supported on very close centers.
Just some thoughts
Rick
Hi Tom, Rick is very right you can also minimize warp by buying lumber at a outdoor local yard or 84 lumber. Why you ask indoor lumber yards such as depot and lowes keep there stores warm especially during the winter. Dry time is increased thus increasing the warp in the southern yellow pine. Most 4x4 are cut from the center of a tree. The center of most trees is the hardest most dense part of the tree. The pressure treating process has a real hard time penetrating these area thus leaving the post very susceptible to early rot.
Just a thought …if PT lumber is a concern with “warpage” why not frame with kiln dried spruce or fir (available at big box stores) only need a good primer and paint it if you wish. It’s getting covered with Trex and won’t have ground contact anyway right?
What Rick said was good advice. You can’t stop PT lumber from warping at least abit as it drys, but using it and fastening it securely right away you can minumize the warping and twisting.
Another good rule of thumb is to check the end grain before you fasten it down. Make sure the cup is facing down and use good long deck screws to fasten it. The wood tends to warp in the direction the grain is running.
The IPP&W in Ottawa has their entire layout built in PT wood and has no problems with warpage as long as it’s fastened down securely.
They don’t make wood like they used to. I recently made 2 small sheds for the RR using a solid chunk of PT 4x4 and a friend got curious when checking it out and so counted the rings. The 4x4 was cut from the center but instead of finding tight rings the first 2 years had almost 1/2 an inch each. That is quick growth so in the long run not as strong.
I once built a small porch with my uncle using PT from HD and boy did it warp, twist and shrink in that first year. I don’t buy from them anymore if I have a big project to do. Instead I go to the local lumber yard and don’t have the warping. Is it better wood at the local yard than found at HD or Lowes?
I’d go with the 16" on center for extra strength.
thanks for the advice and ideas, my trex i ripped in 3in x 10ft pieces and put blocks between about every 2-3 ft, i had 2in pvc pipes every 3.5 ft, the blocks really helped keep it supported between the pipes. so i want to do the same but elevated, i did think about just using regular 2x4`s and painting them, i just thought PT wood would last longer, one side will be held up by landscape blocks and the other by cement blocks.
Tom h
Unless you put that preservative stuff (I don’t remember what it is called, it is green) on the cut surfaces, once it is cut, the PT stuff looses its water/rot resistance, and becomes worse than regular wood.
If you are planning to cut the wood, especially rip it, you are wasting your money to use PT. Use redwood, instead. I don’t recommend using cedar, because it lacks the structural strength of red and other woods.
Tom pictures of the road bed you want to support would be a great help. I think I know what your saying but not sure…I have a raised ladder section on my RR (made of composite ) that is 12" wide and I support it about every 2’ with trex 2x2 balusters
I just have old pics from torn down layout, my blocks were only 2.5 in wide between trex pieces, trex was not flat but on its side, fit perfect over the pipe and bolted it to pipe, was raised about 2.5ft on one end, flat on other, this time have flat yard, need some thing to hold up the length of trex, have it so i might as well use it, had pounded PVC pipe in ground, cannot do that this time so i wanted raised bench like top, i dont think i want to cover whole top with planking, just lets snow and rain sit on top, have a 5ft landscape wall that i will use to hold up one side, then posts or blocks for other side, will run about 40-50ft along wall then have ru in half loops out into yard, kind of like islands out from the straight part.
hope that explains it
Tom H
Old Pics then …please
Tom,
There is a new style of “pressure treated” lumber on the market, but it is not in wide distribution yet. Rather than using toxic chemicals, the lumber is cooked under pressure with silicates and they end up replacing the water. In effect, a composite is made of the wood and glass! It is called Timbersil:
There is a place on the north shore of Boston that carries the stuff and I’ve been meaning to get up there to get a few pieces for testing purposes.
It is supposedly waterproof in terms of rot for the uncut wood as there is a hard surface layer of glass that protects the inner core that has a lower density of the glass infused into it. In fact, an uncut factory post end is warranted against rot if buried in the ground; cut ends to be buried need to be treated with AnchorSeal - an epoxy like product. There are guidelines for installation on their website in a six page pdf.
Don’t know what it costs, but I’m sure it ain’t cheap; the real cost savings would be in never having to replace it or to realign your right-of-way, etc.
Given our requirements, one thing I was wondering about is how tight of a radius could you bend it to - especially given that it has this dense glass coating.
If you do find some, please report back on how it works.
Brian
Taxachusetts
Tom,
I use 16" centers on my benchwork. Trex needs 16" support to avoid dipping as it’s non-structural. This is what’s specified for decks planked with Trex. I’m not a big fan of Trex for a railroad although it is a good decking material.
When you buy PT lumber select each individual piece yourself and don’t buy anything with much warp in it thinking you can correct it by simply screwing it together tightly. Also as noted I never nail it. I use good quality deck screws and even though they’re self tapping I clamp the pieces together and drill pilot holes so they all go exactly where I want them.
All the original benchwork from 2004 is still in use and except for the “leaning rails” on top have had almost zero warpage. If you have any issues with proper installation for your area just look at the decks in your area and that’ll pretty well tell you what works for legs, bracing, etc.
Hey Tom,
Got the juices flowing again, huh? Good to see you posting.
Brian,
IF that stuff is replacing water with silica, that will be hell on saw blades. Silica is tough stuff, use in blasting metal prior to coating. For the hobbyist the cost of saw blades may well outweigh the savings in not replacing the material.
My tuppence worth.
Bob C.
Bob,
I hear you, but according to the product sheets it cuts slowly, but does not shorten the life of carbide tipped blades. And we all KNOW that manufacturers never lie …
Brian
Words from the Pope of Trackwork.
(http://ovgrs.editme.com/files/Track/DeckBlocks.JPG)
“The crown of the deck boards is always fastened face up so they do not cup, hold moisture, and warp or twist. Whenever possible, the boards are spaced as shown above so that the track will run down the center of them and remain level from side to side. A belt sander can be used to remove any irregularities that would interfere with the level of any track or switches running diagonally across the boards. After the track is laid, styrene or popsicle stick shims could be used to level any problem switches or track.”
To read the entire epistle, just click on the link. http://ovgrs.editme.com/Track
Ric, it is finally snow free, i have been ready for 4 months since we moved and decided to build again, my son has the dates of Andys get togethers on the calender already and cant wait to run his train, he is asking every other week “is it time yet”.
It does feel good to get the creative juices going again, cant wait to start building again, i do like the bench approach, if it works in Canada, it will work in Indiana, I like how they did that.
Tom h
Tom,
If you like the “on wood’” approach of the IPP&WRR, check out this site.
This is the railroad at Fred Mill’s that we visit every year. Even the track on the ground is on pressure treated wood. Those guys are very happy with the efforts.
More info on the OVGRS can be found by Googleing
Ottawa Valley Garden Railway Society
Lots of good stuff and ideas.
