Eliminating gaps and/or elevation differences in foamboard

[wvg_ca]

filler would not be required as the track will alleviate the slight differences by itself ...if you want to fill for scenic purposes, the drywall mud or expanding foam spray bomb work well ..

[kasskaboose]

Blue painter's tape works for me to close gaps so does duct tape.  No one notices the tape when it gets covered by paint and scenery. Very minor elevation differences have not been an issue with my trains running.

[richhotrain]

Doughless

Even two sheets of plywood can have a slightly different thicknesses when butted together.

Took the words right out of my mouth, Douglas. I was just about to write the same thing. 

Owens Corning recommends DAP 230 or HVAC Foil tape to fill gaps on 2" foamboard, but I can't help but wonder if simple masking tape wouldn't do the job.

That said, 1/8" to 1/4" differences in height at the joints seem like something more than slight differences. Vertical differences of 1/16", on the other hand don't seem so bad. But, honestly, any differences in height or any gaps easily become problematic.

As careful as I was in building my layout with 1/2" plywood surfaces, all gaps needed to be filled and smoothed with caulk before landscaping or ballasting.

Any height differences at joints are unacceptable. You don't want any humps or valleys in the track work. I run into problems with my yards with height differences no matter how slight. I call them "hump yards" as I watch freight cars and passenger cars roll down the unintended inclines.

Rich

 

[BigDaddy]

Great stuff spray foam is good for filling gaps.  It will expand more than you imagine possible.  I trim it with a razor blade or a razor saw.  You can fill big holes too and trim with a sureform.

I am building on individual modules with adjustable legs.  I can dial out any horizontal differences.

[Doughless]

Even two sheets of plywood can have a slightly different thicknesses when butted together.

I layer cardstock pieces to smooth the transition.  Three , then two, then one etc as you work away from the joint.  Three would mean a pretty big difference in thickness.  Topside to smooth the roadbed, not lifting the foam from underneath.  Roadbed would go on top.

If you're concerend about the cardstock disintegrating when watering for ballast, then sheet styrene will work....and might be a better mate for foam.

[The Milwaukee Road Warrior]

Hi all, I have been placing 2" foamboard down on my benchwork for the last week and have noticed some slight differences in height at the joints, as well as slight (1/8" - 1/4") gaps between sheets due to my imperfect cutting.  What is the best way to address these for smooth(er) operation?

For vertical differences will a sanding block of some sort be able to blend the two together without tearing up the top surface?  The vertical difference is very slight: maybe 1/16".

For horizontal gaps, what is the best way to fill and level the gap between two sheets?  I can of course fill the gap with PL 300 or DAP caulk of some kind, but is there something better I should use?  At one time I thought Woodland Scenics made some sort of foam "putty" filler ...like a spackle for foam...

Thanks.