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I am looking to make some 1 foot square terrain tiles (for 6mm and 3mm models). I want a base of MDF and I would glue on a layer of corkboard which I could cut into to make terrain features (my current plan is to make tiles for a Great War/Vraks trench setting). I was intending the MDF to be 3mm thick and the corkboard also to be 3mm thick.

I have previously tried this sort of thing with foamboard or cardboard but they warp pretty badly. I am wondering if MDF has any possibility of warping (or, if it does, could I put weight on top of it to completely eliminate the warping)? Nothing worse when making stuff like this than terrain boards which are not level due to warping.

Anyway, if it is relevant, these are the MDF pieces: https://www.tilgear.info/materials/wooden-materials/wooden-craft-parts/mmb300p10-mdf-model-base-300-x-300mm-pk-of-10 and these are the corkboards: http://www.wickes.co.uk/Wickes-Sealed-Cork-Floor-Tile-305-x-305mm-Pack-9/p/620950?CAWELAID=120135120000015101&CAGPSPN=pla&CAAGID=52608969584&CATCI=pla-305307848379&gclid=EAIaIQobChMI8Kvd64ae1wIVCuMbCh3okQ8tEAQYASABEgICQ_D_BwE&gclsrc=aw.ds

MDF will warp a great deal if you get it too moist (e.g. buttering it in pva), but iirc you can varnish/seal it first to get around this.

Yes, very possible.

Use strong glue, but sparingly. You can "seal" it as well. Also i f you're going hardcore into tiles - consider framing them underneath somehow. There are some companies who make MDF tiles with a frame to them I believe.

I tried glueing a big piece of foam down on a 3mm mdf tile with watered down pva glue and it warped quite abit.
I threw it away. In hindsight the more moisture the worse it is.
And the smaller terrain pieces it warped just abit so it didnt bother me.
Thats the only experience i have, can only confirm that there is a tendency to warp.

MDF will both swell & warp when water is applied. The solution is easy - don't use water-based glues like PVA. CA glue works fine in small areas, or you can get small amounts of of construction adhesive (like Liquid Nails) at local hardware stores. It won't shrink as it cures, so it won't warp the MDF. For larger pieces, like terrain, get a caulking gun for about $5 and buy it by the tube. It's much cheaper that way.

3mm is pretty thin for MDF. As other have said, it will probably warp if it gets too wet.
Thicker sheets would warp a lot less. The only big drawback is the added weight.
You could also go with plywood, which is a bit more stable and lighter.

Last time I did terrain tiles in MDF (actually, it may have been HDF), I selected either 12.7mm or 19mm thick stock. I used foamcore glued down to it, secured with (IIRC) Liquid Nails.

I've also heard of people using spray adhesive to secure cork toppage to the base tile, and then further secure it with watered down PVA - I have not done this, though.

M.

Cheaper MDF can warp if you take a band saw to it.

Get a hot glue gun, they are only about a fiver and are very easy to use.

I've made tiles of 5mm mdf with very little warping. 3mm is a bit too thin. As much as moisture will soften it and make it easy to warp, the material itself will bow with gravity alone if you don't leave it flat (ie storing it leaning up against something will lead to a distinct curve to it).

A couple of thin coats of PVA brushed on with a decorating brush, allowing each to dry thoroughly before painting is advisable - unsealed MDF will drink paint like crazy, especially on larger areas.

3mm MDF is fine for small pieces of scatter terrain (no more than around 3"-4" diameter, or buildings as the frame of the building will brace the piece), but larget pieces or actual tiles will want something thicker.

Honestly for Terrain tiles I'd suggest going for thinner plywood instead, for strength. Especially if these are going to be heavily used. You can get your local hardware store to cut a sheet up for you (If you do, be aware of the kerf, the space the sawblade goes through, will cut out roughly a 1/16"-1/4" or so of material, depending on the sawblade). Also check that any sheets (or pieces) you buy are straight before you buy or have them cut; a lot of times they are warped in themselves (this can really depend on the quality of what your local hardware store stocks). You want to look at the piece along all its edges, sighting along, to make sure there's no curvature or warping.

otherwise what everyone else said about MDF

The top of my gaming table is MDF pieces, about 5mm I think. I sealed them with a latex household paint and primer.

MDF is basically wood-chips/dust formed together with resin..

Some of the more negative properties:
- Denser than plywood or chipboard (the resins are heavy)
- Low grade MDF may swell and break when saturated with water.
- Subject to significant shrinkage in low humidity environments.
- Painting can be difficult due to rapid water absorption. Most finishes appear uneven.

If you ever had laminated MDF furniture you would only have to set a wet glass on it to know for sure.
I usually attach whatever I need to the surface and then prime it both sides.
Some people I know smear on white glue as waterproofing and then a quick sand to smooth it out.
Usually what happens is people forget to seal the side that faces the table and even humid air can cause the MDF or cardstock to swell.

Thanks for all the advise. I think I will try something other than MDF. Perhaps birch plywood, 3mm: https://www.tilgear.info/materials/wooden-materials/birch-laser-ply/bpy363p10-birch-plywood-sheets-laserable-600-x-300-x-3mm-pack-of-10

Just an FYI, plywood can warp as well, especially the cheaper varieties you get from hardware stores but even the more expensive varieties we use at work from industrial suppliers.

In fact one of the pros of MDF is that it usually warps less than ply, because ply is made from lots of layers of wood that can shrink/expand/soak up moisture at different rates.

The benefit of plywood is that it's stronger and stiffer for the same thickness, but MDF is usually touted as having better dimensional stability.

To help prevent warping you could try painting the whole thing with an enamel paint first, paint both sides and the edges. Enamel paint is oil based so it might give better results than a water based paint (as far as not causing warpage itself and also preventing moisture getting in to the wood).

Another option might be marine grade ply, I couldn't tell you if it better resists warping, but what makes it "marine" grade is they use waterproof glues like epoxies when they stick the sheets together.

I've used 3mm MDF and mad a game board out of it, 2ft x 2ft. I painted both sides with sealer, and put some weight on it to prevent it from warping. After 4 years and living in an low humidity climate I have a slight bend in it.

I've heard of framing each tile to prevent this might be worth it.

Another thing with MDF is that it can sag. Similar but slightly different to warping. If it's kept in a position which isn't perfectly flat and puts a sag in it after a while it will permanently take on the bend.

It's less of a problem for bases but more of a problem for large thin pieces used for gaming tables, benches, etc.

what I usually do to prevent warping is drilling wholes in my mdf bases. If it soaks up moisture,it can expend there more easily and therefore prevents warping. It will still warp if you go overboard with paint / pva / water.

I also prime it with gloss varnish first to harden it.
Always put something heavy on it while it dries.