Roof material of 40' boxcars ?

[Biased turkey]

Is the roof of 40' boxcars made of galvanized steel ?
I know the roof of 50' boxcars is.

Jacques

[slekjr]

I'll try 1 more time first 2 went to cyber world.
We have a 40 foot PRR X29 that has a plain steel roof.
Charlie

[Squidbait]

It depends. Later box cars were all steel, but earlier ones would have had a wood/canvas roof.

Chances are if it has steel sides, it'd have a steel roof.

[doctorwayne]

Early metal roofs, called outside metal roofs, were simply sheet metal applied over the original wooden roof. Eventually, pressed steel roofs became available from several different manufacturers, each with its own distinctive pattern. When a railroad ordered a batch of boxcars, they'd specify which proprietary roof they wanted used, sometimes choosing to equip part of the order with one type and some of the cars with another. I'm not sure when galvanised roofs came into common use, but before that, many cars had a waterproofing material applied to the roof (and sometimes the ends, too) called roofing cement. This contained a tar-like substance and was often (but not always) black. It was applied only to the roof itself, not to the running boards, so the running boards might be painted black, or painted the same colour as the carbody.
Galvanised roofs were originally painted in whatever colour the railroad specified, but the paint didn't adhere well, so eventually it was eliminated. Since the cars are not masked for painting, new cars often show overspray of the car's colour along the edges of the roof.

Wayne

[Squidbait]

Looking into this a bit more, I think it's safe to say that any car built after the late 1930's would have had a steel roof. The question is whose roof panels would they have used? Boxcars 101 from the NMRA answers most boxcar-related questions.

[Biased turkey]

Thanks Charlie, Squidbait and Wayne for taking some of your precious time to reply.
Boxcars 101 is e very informative link.
I'm modeling the transition era so it looks like galvanized steel roofs is the way to go. I asked the question for weathering the boxcars roof. In the case of galvanized steel I cant paint some roof panels with aluminium paint and a black wash + some rust.

Jacques