Hiding joins in foamboard

[andyste1]

I’ve been experimenting with foamboard, having removed the paper coating, then scribing a brick pattern into it. I’m pleased with the results so far on small patches, so I’m now ready to move on to constructing a small building.

It makes sense to scribe the walls before glueing them together, but I’m not sure how to “finishl the corners. I think it’ll be tricky to continue the pattern across the end of one foamboard piece, then lining it up with the pattern on the next wall. There’s also the join/gap to deal with. Any suggestions?

Alternatively, I’ve seen a technique that involves constructing the building first, then applying a thin coat of polyfilla all over and scribing into that once dry. I know this is used for stone walls, but I’m not sure of it’s suitability for brick (i.e. getting an even layer of filler).

 

[Andy Hayter]

I think covering foamboard with plaster only makes sense if foamboard is the cheapest construction material you have available.  In my case it isn't since I made a point of visiting every office locally in our company every January and relieving them of last year's calendar - usually backed with a sheet of Bristol board, great for constructing buildings.

 

However back to foamboard.

Lay out your design for all four walls (assuming this is a simple box building) side by side and connected as if it were a single wall.  Mark out all of your scribing, making sure you get things right where each wall ends and the next one round the corner begins.  Now cut out the rectangle and then split into the 4 individual walls (make sure you know which ones are linked to which.).  Now chamfer the ends of each wall to 45 degrees so that  the walls join cleanly in a right angle with its neighbour.  Until you get really good at this - and probably afterwards too - you will end up with fine gaps at the join which can be filled with the fine filler of your choice - polyfiller, squadron, etc..

[andyste1]

It’s probably worth adding that having just seen some videos of people working with foamboard, it’s dawned on me that I hadn’t entirely removed the paper. While it peeled off easily after wetting, it seems to have left a very thin, smooth matt layer behind (the adhesive used to glue on the paper perhaps?). The foamboard is from Hobbycraft by the way (“Westfoam” brand).

 

It’s this layer that prompted me to ask how to handle corners, as there will not only be a narrow gap between two walls, but the “real” foam at the end of one wall section will also be exposed, with a different texture to the rest of the wall (and won’t scribe in the same way). Perhaps I need to find myself a better brand of foamboard that will allow me to fully strip the coating...

 

This matt layer does provide some interesting effects though, as it “cracks” when you scribe it, resulting in a nice rough/rustic brick effect, with (say) a sharp screwdriver or back of a scalpel, while the blade itself produces a clean, modern brick mortar effect. I’m working in OO by the way.

[Andy Hayter]

47 minutes ago, andyste1 said:

 

 

It’s this layer that prompted me to ask how to handle corners, as there will not only be a narrow gap between two walls, but the “real” foam at the end of one wall section will also be exposed, with a different texture to the rest of the wall (and won’t scribe in the same way). Perhaps I need to find myself a better brand of foamboard that will allow me to fully strip the coating...

 

 

That should not happen if you follow my advice about chamfering the end joints to 45 degrees*.  There are two reasons for doing this:

1.  It avoids that problem of potentially different textures - even if you do properly strip the top coat, you will still have the back coat giving a vertical discontinuity one board thickness in from the end.  This is much harder to hide than a join at the very corner unless you run something like a downpipe to hide it.

2.  You have a bigger glue surface and hence a stronger building.

 

*  This gives you the same sort of joint as you might find in say the body of a Parkside or Slaters wagon kit

[Silly Moo]

Have a look at the new super lightweight fillers that have become available. I tried a brand called One Strike, the first impression you get is that the tub it comes in is empty! The filler itself is very soft and light,  a bit like marshmallow, it dries quickly and can be painted soon after it has been applied. 

 

I have found it useful for filling gaps in styrofoam scenery and I’m sure it would work well with foam board. It’s worth getting a tub to experiment with, if all else fails you can use it for filling holes in the wall.