Foam board base

[Wallydog]

Hi im fairly new to modelling (4mm) i am planning a small diorama (approx A4 size). I am going to use foam board for the base. Do you need to prepare it in any way before adding the scenery? I.e do you need to rough the surface to make items stick. Also can you apply papermache / grass type sprinkles directly

Hope this is not a silly question but any help and guidance would be appreciated

Thanks

[Geep7]

Here is a photo of my first HO American layout Mason's Bridge Yard.

 

 

Hard to believe but the main baseboard structure is all 5mm foamcore board, but it was reinforced with ply and softwood at the baseboard joints, which you shouldn't need to do for a diorama.

 

I don't recall having to do anything special with the foamcore, I just put the scenery straight on top. Just ensure that you put enough bracing underneath, and it should be fine. I'll see if I can dig out some under construction pictures.

[Wallydog]

Brilliant thanks very much for replying

[wasabi]

Foamboard (or at least the type I bought) doesn't like moisture.  So I would advise putting some sort of barrier material down before using products like Mod-Roc.  I model in N and use Kato track - they have ballast products that seem to work alright but I would be cautious about using watered down products (PVA?) on pure foamboard.