[PrairieKnight]

I built an addition to my layout. On top of the 1/4 plywood top of the bench work I adhered 1/2 inch green insulation board from Lowes. I had to cut and piece it together to cover the entire surface of the plywood. I secured the various pieces of green insulation board to the plywood with Liquid Nails. What has anyone used to fill in the gaps between pieces of green insulation so that it does not like I have fault lines on the layout? I was thinking of using spackling. Has anyone used anything else that worked well?

 

[All-Scale Railfan]

Latex caulk works well. If you have larger gaps, than a few layers may be necessary since the stuff settles as it dries. It's also water cleanup so it's easy to work with.

 

[shortwrench]

Latex caulk works well. If you have larger gaps, than a few layers may be necessary since the stuff settles as it dries. It's also water cleanup so it's easy to work w

I built an addition to my layout. On top of the 1/4 plywood top of the bench work I adhered 1/2 inch green insulation board from Lowes. I had to cut and piece it together to cover the entire surface of the plywood. I secured the various pieces of green insulation board to the plywood with Liquid Nails. What has anyone used to fill in the gaps between pieces of green insulation so that it does not like I have fault lines on the layout? I was thinking of using spackling. Has anyone used anything else that worked well?

I use drywall compound applied with a flux brush. Not picky about trying to get it real smooth. When
you apply ground cover, dirt, and bushes to it; it mimics most real world scenarios which are not
perfectly flat. After it dries, if you need it real flat, light sanding will smooth it down.

 

[CTValleyRR]

Drywall mud, spackle, spray foam, WS Plaster paste, plaster, Sculptamold. The possibilities are endless.

 

[Old_Hobo]

Or, don’t worry about it at all, if you are going to build up the base with scenery, hills, mountains, trees, etc…..

 

[Steve on Cattail Creek]

I built an addition to my layout. On top of the 1/4 plywood top of the bench work I adhered 1/2 inch green insulation board from Lowes. I had to cut and piece it together to cover the entire surface of the plywood. I secured the various pieces of green insulation board to the plywood with Liquid Nails. What has anyone used to fill in the gaps between pieces of green insulation so that it does not like I have fault lines on the layout? I was thinking of using spackling. Has anyone used anything else that worked well?

As others have said, the possibilities are endless, and anything that is both compatible with the foam (petroleum-based products are generally a Very Bad Idea for use around any type of foam!) and provides adequate support for the landscaping above will do fine. In fact, if you're planning any sort of substantial top covering (landscaping rolls, plaster of paris cloths, sculptamold, ModPodge, etc.), you might be able to just roll over the seam and cover it at that stage, rather than pre-fill it as a separate step. However, if the plan is to just do a base coat of paint before, say, adding some dirt, static grass and scatter turf over a layer of glue, it probably would be best to pre-fill in any voids and obscure the line of division. You can always back and fill later, but IME it's almost always a lot easier to avoid the problem than to try to correct it later! Good luck!

 

[PrairieKnight]

I appreciate the replies. Here are a couple pictures before I filled in the cracks between the insulation pieces.

Here are a few photos after I applied latex caulk to the cracks

Although I will not get any style points for being neat, I agree with Hobo that there will be ground cover, trees, and structures to blend everything together. The caulk was very easy to work with.