# Concrete backer board as roadbed ???



## Dave F (Jan 2, 2008)

Anyone tried this? 

It's become apparent that I need to redo all my roadbed (already). I need a more consistant support under my trackage. I also need it to be somewhat water/weather proof. One idea that crossed my mind was to rip a sheet of concrete backer board into 4" strips (each 8' long), stack the strips three deep (approxamately 1") and use as roadbed. I'd overlap the ends of each layer about a foot or 18" to form a more unified roadbed. I could easily cut radiused pieces for the curves as well. 

Any thoughts or feedback before I spend my few remaining pesos on backer board?


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## Jerry Barnes (Jan 2, 2008)

There have been posts about using it in here before, but mostly only one thickness. You might have a good idea! I have one layer under a switch that has been outside for over a year and it still seems to be fine.


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## placitassteam (Jan 2, 2008)

I built several switches on 1/4 inch thick backer board. after four years the board is starting to delaminate, seperating into pieces about 1/16 inch thick. It also is not very easy to level, I had to use a layer of sand to get it level. IMHO it is not worth the trouble.


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## imrnjr (Jan 2, 2008)

Rather than backer board, I used HardiPlank 4" and 6" trim board. It is already 3/4" thick and comes in 12 foot lengths." border=0> 
For support I drill it every 30 inches with a 1-3/8"diamond hole saw which allows 1" PVC for support posts and set a 2x4 block (drilled with a forshner bit under it to screw thru to the PVC. 
A 4-1/2" diamond cut off saw in my small hand grinder cuts it and I utilize 1x4 PTL appearance board cut about 6" long for connecting support between the Hardiplank. 
It's very simply, rock solid, easy to level, and just a modification of the "ladder" method." border=0> 
Mark


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## Dave F (Jan 2, 2008)

Ohhh, great suggestion Mark, thanks. I'm pretty sure they have that at my local Home Depot too.. I'll have to look into the cost & see how it stacks up.


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## Richard Smith (Jan 2, 2008)

Dave, 

You might only need more joists beneath the roadbed. I use them every 16" and support blocks every 8" between the laths. You might even need more for heavy snow regions. The laths are cedar 1-1/2" deep by 5/16" thick and have held up beautifully here in the wet NW. I do prime each lath. Remember too that the concrete backer board weighs quite a bit and if their is insufficient benchwork support it too will sag. 

Using material as you're thinking should work too but you lose the whole advantage of the ladder track method, namely easy to form flowing curves without the need to cut everything to shape. If I was going to do it that way I'd be more inclined to do as the guys in Canada on the IPP&W do and use 2x PT or cedar material screwed down although Mark's method sounds plausible as well. 

Whatever method you use don't skimp on materials. Shortcuts usually lead to doing everything over and costing much more in time and money than doing it right the first time.


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