Track underlay - how wide?

[ejstubbs]

When cutting cork or closed-cell foam sheet for track underlay, what's the best width to aim for?  To put it another way, how much shoulder should you allow beyond the sleeper ends at each side?

 

I've had a look at various suppliers of pre-cut straight cork underlay and there seems to be a range of widths offered for OO guage.

 

If it makes any difference, the track is mostly Peco Setrack, with Streamline code 100 points.  It will (eventually) be ballasted.

[sharris]

Typing 'track ballast width' into google and doing an image search will bring up many many diagrams.

[ejstubbs]

Well indeed - but that's part of the problem.  There are many, and they don't by any means all agree.  That's why I was hoping that someone would be able to recommend a good general-purpose figure.

 

However, these two links (link1, link2) do seem to reference the same diagram, which looks straightforward enough:

 

 

1'0" is of course 4mm in OO.  I am planning to use 3mm closed-cell foam underlay, so I reckon that cutting it 3mm beyond the sleeper ends should work.  I'll be cutting the foam square rather than chamfered, and relying on the ballast to fill in the wee corner along the edge to make the correct sloping profile.  With a ballast depth of ~1mm on top of the underlay, that should give me roughly a 4mm shoulder, starting roughly 4mm out from the sleeper ends.  I think.

 

Anyone have any contrary views?

[The Bigbee Line]

If your doing a manicured main or branch line it's all part of the look to have a neat and even shoulder. In yards it's not usually necessary. Quite often there are some interesting differences in track levels.

[28XX]

Bear in mind that in 00 using Peco geometry you have some compromises already. Nothing wrong with that, the majority of modellers do, but consider how adjusting the prototype dimensions above can help the appearance, or hinder it.