Is MDF ok under homosote as a roadbed material?
it has a little more flex than plywood.
what about OSB?
thanks
TPL
PL, the answer to MDF is NO. It is not designed to be used in a horizontal application. It is very prone to sagging. Also, it doesn’t hold fasteners very well.
OSB is not the best, but it is better than MDF. I have been considering using it on my upper deck, but I haven’t made up my mind yet.
MDF also requires special blades when cutting/drilling to prevent chipping/breakage and it produces a lot of dust. It is also heavier than plywood. OSB has a tendancy to sag in horizontal use when placed under load. If you go that route, add an 1/8 to 3/16 inch in thickness to help stiffen it. When you consider the cost difference per sheet, what’s the point? You can use B/C plywood for trainboard since no one will see the surface anyway.
TPL,
I would go with 5/8" or 3/4" B/C ply. Depending on your frame work.
Then cover that with your Homesote or insulation board (pink or blue).
The real advantage from MDF is in the landscaping section. You can build the frame’s for mountains and other substructures with it, it’s very good to glue with woodglue or hotglue (works fast and is stable). As said before, MDF is not a rigid ground to build your railroad on. I used OSB, which is the cheapest material in Holland for constructions, and I used the 18mm thick ones. It’s in use under different layouts now for about a year and no sagging or moisture problems with it.
MDF will also swell fairly rapidly when exposed to liquids. I agree with others about horizontal strength. It will NOT hold the weight of your average adult male.
Mark
I’ve never had any problems cutting or drilling MDF with ordinary tools. Never had any chipping, etc. But I do know from experience that it doesn’t take screws very well. I experienced splitting around the screws, but to be honest, If I had predrilled the screw holes, it might not have split.
I used 1/2 plywood over 2x4 joists spaced 2 feet apart. I’m not worried about it holding full grown people. I don’t intend for any to be on the table. Also, my entire benchwork and plywood tops cost me nothing. All the material was scrounged/recycled from construction projects. Anyone ever consider breaking up palets for joists or legs or bracing? People give them away all over the place here.
Jim