Mdf Or Plywood?

[Bramleyboy]

I want to build a model railroad around a room on a shelf (not yet installed) about 300mm wide. Should I use MDF or plywood and would 18mm MDF do and if so, how far apart should the supports be? If you recommend plywood what thickness should I use? Does MDF 'slump' or warp, I don't think plywood does. The railroad is not heavy!

[Old_Geezer]

I would have thought whatever you preferred would be fine. You can tell how far apart the supports should be by loading your shelf with your railroad and seeing how much the self flexes/bends before committing yourself to screwing them to the wall.

[The Builder]

MDF is the cheaper option. It's quite heavy though. For bookcases, I usually have support at around 300mm (12"). Your load is not so much though.... say 450mm (18") apart for 18mm MDF

Joinery ply is much more expensive. Go for shuttering ply, also called sheathing ply. Maybe a pound or two more than MDF.

Another idea is to glue and screw 2 x 1 (25mm x 50mm) planed batten to the edge (2" face being vertical). This will strengthen the board substantially. Nothing should warp then. With this, you could reduce the supports to 600mm (24"). It also covers up the cut edge of the ply.

I think I would use MDF with the edge batten.

[heathfield]

You'll want the shelf to be as firm and solid as possible to ensure that there'll be no movement at all to the track once it's laid. Forget MDF. It's liable to sagging and is affected by temperature and humidity, plus waterbased paints and adhesives won't do it any good either. Use 3/4" ply. If you've a stud wall, place the brackets on the studs, which will probably be every 16" (40cm). Use a stud-finder if necessary. If it's a solid wall, just use the same spacing.

[Bramleyboy]

Thank you. It's difficult choosing the best answer because both Heathfield and the builder told me what I needed to know.

[chas2008]

Im with the builder
i would have gone for the MDF purely as its easier to pin / tack things to, ie track.There is no problem painting it, just needs a suitable primer.
Ply has a habit of flexing/bouncing when tapping nails into it,it can also have some nasty edges that would need tidying up, most railway/scalextric layouts i have seen have been on mdf.