Terrain boards - construction advice needed (warping!) - edit: problem solved?

[Charlie_]

Ok, let's get this terrain board problem sorted out!

A little background - I started building boards and terrain about two years ago, kind of experimenting as I want. 2017 I played my first games on them. Now in 2018 I want to review the terrain I've built, decide what I need to do next, and what things need to be re-done or just thrown away.

The main problem that has bothered me throughout is getting my modular terrain boards to line up together nicely. Overall I am happy with the results, and I've come up with a few cunning plans  along the way which have helped, but the real problematic one are the big 2x4 boards, and I want to sort this out!

Here's a pic of my assembled gaming table, featuring a mix of 2x2 and 2x4 modular boards, of which there have been many more built since this pic was taken. You will see they sit on two drop-leaf tables, with a bridging piece between them which is bolted to the two side pieces.... This has the bonus of keeping everything together so they don't slip apart. Another bonus is I can wedge in little bits of folded up card to adjust the height of boards at the corners where they aren't matching up right. I'm very pleased with this table construction - it's designed to be disassembled and packed away easily.



Here's one of the 2x2 flat, plain boards.



They are made of 9mm MDF screwed to a frame of 20mm square battens. In the next pic, you will see how I made the first few (on the left), before I realised it was much better to do it like on the right, with the battens set in 10mm from the edges. It meant I didn't need to worry about getting the battens perfect, and as long as the MDF boards had been cut properly at the DIY store I could trust that the finished product is perfectly square.



As you will see, they go together rather nicely. I have realised it will be IMPOSSIBLE to have no joins visible, and with that in mind I am more than happy with this finished result.



But it gets trickier with boards featuring ditches, streams and other depressed features. For these, I turn the construction upside down, so the MDF is the base, the battens form the edges, and 20mm thick blue foam is placed inside them.



A nice finished product, but it means I've been trying my hardest to get the edges perfectly square and straight. I haven't quite managed it, as you can see on this pic -the gap looks a bit too wide for my liking.



I've found a product that might solve this problem! An edge-trimming plane, which will allow me to make sure the edges are perfectly square, and the finished boards will line up with minimal gap. I'm gonna definitely buy one of these when I make my next boards, and perhaps even go back and carefully plane the edges of my finished problem boards.



But the big problem comes with the 2x4 boards. I could just stick with 2x2 boards, but I do definitely want some 2x4s in the collection. Firstly because they will mean less visible joins on the table. And secondly because it means my roads, rivers etc can have longer, more natural curves rather having everything making sharp 90 degree turns. Here's an example of what I mean.



  But I can't seem to make any 2x4 boards without them warping. They just won't lie flat. Look at how I constructed them from underneath. The one on the left is one of the first boards I made over a year ago, and I was annoyed to find they had warped. The one on the light I made recently, trying a different construction.... I was super mad to find out that this one warped MUCH MORE. Looking back, the slight warp of the first one I can cope with, by using the folded-card technique to wedge them tight so they don't rock back and forth. The warp on the new one is too much though. So I need to rethink before I build more 2x4 boards.



The battens are attached with both PVA and screws. On the recent board I made sure to put very minimal PVA on, in small dots rather than slapping it all over. I also made sure that the battens were perfectly straight - about half of the ones I buy are already bowed, but I made sure this wasn't an issue with the new board. The top is textured with filler, painted, drybrushed and washed, then watered down PVA is used to afix the flock, and then a coat of watered down PVA sprayed on to seal it. You'll note I've also tried sealing the boards underneath with black primer before construction.

I was under the impression that with the primer seal, minimal PVA, coating with filler before painting and flocking, and making sure the battens are dead straight, I would keep warping at bay. It would appear not.

I don't know what's causing it. Could it be the battens themselves??? Would the boards be better off with no battens, just the MDF board?

Here are some things I am considering trying....
- No battens. To get them the right height, I just need to lay something of equivalent thickness underneath.
- Thicker MDF (18mm), with no battens. I will need to lay a light piece of 11mm board underneath to get the right height - I've found some 11mm chipboard which will do the job. Surely 18mm MDF won't warp? The problem with this is they will be very heavy, and harder to handle.
- Different construction. I'd need advice here - if anyone knows the perfect construction that will reduce warping, tell me! More battens? Different layout?
- Building them as if they were having rivers etc. So the MDF would be the base board, with just the battens and 20mm blue foam afixed. There will be no filler, no paint, and very minimal PVA contacting the MDF. Surely then they won't warp? Would make them a little harder to handle, but has the bonus that I can add little depressed features, and I will be doing at least one like with a river some day in the future anyway.
- Construct them as normal, but screw them to a big heavy board all the time I am texturing, painting and flocking. Don't unscrew them until they are 100% finished and dry.

So I have two problems preventing my terrain boards being perfect. The first one I think I can remedy with the edge-trimming plane. The second one though, I need to rethink how I am building the 2x4 boards if I want to solve it.

I would appreciate any advice form people with experience of making terrain boards, or just anyone with better carpentry knowledge than me who might be able to shed some light!

[Silent Invader]

I assume you’re storing them flat? (I think I read elsewhere that you do)

I’m actually moving away from 30x 30 in 6mm MDF to 60x60 in 18mm marine ply. I’ve yet to find out if it will make a substantive difference.  Other than that, I share your pain. 

[levied troop]

I imagine sharing the pain will be a common theme 

Have tried most of the options you suggest with varying degrees of success.  My last boards warped badly and I was discussing this with a couple of fellow gamers at the Tonbridge show.  They felt that modern MDF isn’t constructed that well and I must admit my older boards have fared better.

I’d go for thicker, 18mm, and batterns.  The ones I have like this have survived best and if I’m using sculpted terrain in the future I’m going this route (although I’m going mats at the moment).

One set of boards we’ve been using at shows as an underlying set to help raise the game up are 6mm MDF that were thoroughly varnished.  They must be 20 years old now, stored on end, not battened and haven’t warped.  But they are plain and haven’t had foamboard, PVA or flock added.

[Silent Invader]

To be honest, I’m in two minds about using a mat instead of the 18mm marine ply for my current projects. I have tried adding a plastic angle bracket at the board edge, which is nice and straight, but which still seems to pull in a bit at the top. I suspect that adding angle iron to the board would give certainty but weight etc becomes impractical.

[FifteensAway]

Not angle iron - angled aluminum, lighter weight.

I stick with underlayment sandwiched top and bottom to battens and haven't had warping yet, carefully stored dead flat.  Could add ditches and such with a bit of planning and careful placement of interior battens. 

[OSHIROmodels]

You could try and glue some single sheet newspaper to the underside of the boards with watered down pva/wood glue to help counteract the warping.

[Silent Invader]

Not angle iron - angled aluminum, lighter weight.

I was thinking that Ally angle might still have some flex at the 4 foot length being considered so went for the bombproof extreme   

[SteveBurt]

My boards are insulation board or 9mm MDF with static grass, and the river boards are thinner 6mm MDF with cork tiles on them.
No warping at all after 20 years or more. They are stored in a big stack (since they have no terrain on them which sticks up).
Insulation board (or SunDeala board) I think is better than MDF as it is much lighter.
I think the battens might make life worse; if there is a temperature change the wood battens will expand/contract at a different rate to the MDF, and the boards will warp. I would avoid mixing MDF and battens for anything which is going to be subject to temperature or humidity changes.

[Charlie_]

I assume you’re storing them flat? (I think I read elsewhere that you do)

The square ones are flat, stacked in the corner of the room. The 2x4 ones are not though, they are leaned up against the wall. I'm dubious as to whether that's the problem though - surely that can't account for such a serious warp. And the older ones which have been leaning there for over a year have a very minimal warp - it's the new ones that have been there for just a month that are the worst.

I’d go for thicker, 18mm, and batterns.  The ones I have like this have survived best and if I’m using sculpted terrain in the future I’m going this route (although I’m going mats at the moment).

It certainly is tempted to start from scratch and build some new ones with a super-heavy construction! But though weight and transport isn't really a problem, I think 18mm MDF PLUS a 20mm foam/batten layer would just be too much, and seriously reduce available storage space.

You could try and glue some single sheet newspaper to the underside of the boards with watered down pva/wood glue to help counteract the warping.

Good idea, I think I might give that a go to see if it remedies it a bit.
- What's the relevance of the newspaper though? Why do I need to glue that, rather than just a layer of PVA?
- The 2x4 boards have warped DIAGONALLY, so it's two opposite corners which are lifted up. If I wanted to strategically place the PVA underneath to fix it, would I want to apply it just between the two uplifted corners?
- Hopefully the battens won't be a hindrance to doing this - I've heard of doing this as a simple fix for warped terrain bases, not not full boards with battens.

I think the battens might make life worse; if there is a temperature change the wood battens will expand/contract at a different rate to the MDF, and the boards will warp. I would avoid mixing MDF and battens for anything which is going to be subject to temperature or humidity changes.

It's possible, something I've considered .
This is the problem though - I spent all last night reading up on this, and found loads of good threads on it over at TMP, but there are lots of people who VERY CONVINCINGLY argue for one thing of the other being the problem. You say the battens are the problem, and that sounds reasonable. But another guys argues that you HAVE to use battens, and has NEVER had a warping problem since he started doing it this way. What am I to do? 


I had a play around with the boards last night and came to a few conclusions.
- The 2x2 boards are all warped ever so slightly, but not enough to be a problem. They are a success, and my table construction means card shims can be used to raise and lower corners where little problems do arise. And the ones with foam and recessed features are a success too - the edge-trimming plane will be a worthwhile purchase though so future ones I make match up even better, and I can cautiously try planing the edges of the existing ones.
- The two older 2x4 boards are warped, but not so extreme it can't be remedied with card shims again. Annoyingly it's the two new ones with a much better flocked surface that are warped severely. They can also be used as part of the gaming surface, but currently they can only really be placed as end pieces - they can be shimmed so one long edge is level, but the opposite one is up high. When I next make 2x4 boards I need a new construction method.
- I want to keep the thickness of my current boards (29mm total), for weight and storage issues, so won't be starting again.

I think for my next 2x4 boards I will switch to using just a sheet of 18mm MDF, with a piece of 3mm chipboard placed underneath loose to get the required height to match the others. Crucially, when I am texturing, painting and flocking, I will screw them to another identical 18mm board. SURELY they can't warp then. They will not be unscrewed until they are 100% dry!
I won't think about 2x4 boards with recessed features (streams) for some time, and for now just do them on 2x2 boards - but I will want at least one 2x4 river board eventually.


Also at the same time I am having a big storage re-organise to coincide with my kitchen being redone and lots of stuff being moved around my flat, and getting some new furniture. When it's all done the 2x4 boards will be able to be stored flat, under my bed, rather than leaning against a wall.
(I'm also gonna throw out or give away some of the first terrain I put together that I've ended up not using much - if anyone is interested in picking up some trees and stuff from Partizan this year send me a message!)

[OSHIROmodels]

Good idea, I think I might give that a go to see if it remedies it a bit.
- What's the relevance of the newspaper though? Why do I need to glue that, rather than just a layer of PVA?
- The 2x4 boards have warped DIAGONALLY, so it's two opposite corners which are lifted up. If I wanted to strategically place the PVA underneath to fix it, would I want to apply it just between the two uplifted corners?
- Hopefully the battens won't be a hindrance to doing this - I've heard of doing this as a simple fix for warped terrain bases, not not full boards with battens.

The newspaper shrinks quite a bit pulling the board the opposite way as the glue dries. The warping can carry on for quite a while so nothing is a quick fix unfortunately. Regarding the diagonal batten I would suggest a wide strip of newspaper from the corner without a batten to the centre of the board (say 2-3" wide). In future always have a cross batten underneath and make sure that it has a point that fits into the corner.

All the above is personal opinion from from experience, that might be other, better ways of solving the warping 

[Captain Blood]

Got to say, I’ve got about a dozen MDF terrain boards (thin MDF 3 - 4mm maybe?) and about the same number of styrofoam slab terrain boards. I’ve never edged, reinforced, braced, battened or treated any of them, but I have covered them with sand, paint, PVA, flock, fixative, and all sorts of wet and dry surface textures. I’ve never had a single incidence of warping. Maybe I’m just lucky, I don’t know. I store my MDF terrain boards flat on the floor in a stack. The foam terrain boards I store on their sides.
They all sit flat as a pancake on the table when I lay them out.
So why some people have such troubles is unfathomable 

Maybe it’s to do with the heat and / or humidity in the place where they are kept. Mine all live in the garage. It’s cold or cool and dry the whole time, although the upstairs gaming room can get warm in the summer.

[FifteensAway]

If you are leaning 2'x4' boards against a wall - and triply so if the short edge is on the floor - I can pretty much guarantee warpage of just about any wood product as a natural reaction to the forces of gravity.

One thought, what sort of wood are you using for your battens?  If it is soft wood like pine or its 'modern' substitute 'white wood' (whatever that is), you are going to get warping.  I always use hardwoods which are more expensive but much less likely to warp.  I also both glue and screw my battens - doing my best to countersink the screws so they aren't sticking up above the flat surface.  Then some wood putty, some drying time, and some judicious sanding.  Yes, a lot of work but if you want a quality result, it takes time.

However, the best trick to eliminate or at least minimize warping is flat storage.

[Silent Invader]

One other thing to bear in mind is that the warp might have been introduced pre purchase. A couple of times I’ve been to B&Q for more tiles and seen the MDF sheets on just a couple of battens, sagging in the middle or at the ends of all three, so have given it a pass. But it’s quite probable that I’ve purchaed sheet that had otherwise already developed a faint bend.

[levied troop]

Maybe it’s to do with the heat and / or humidity in the place where they are kept. Mine all live in the garage.

I suspect that’s a major part of the problem, I don’t recall having significant issues in my previous house with a garage but currently I’m relying on a big shed.

I like the sound of the newspaper idea, I’ll give that a try on a one set of boards I have that show a slight bow.

[OSHIROmodels]

Just a single sheet/layer should do it with watered down 'glue of your choice'.