Expandable Foam?

[btrain]

Since I'm not the most gifted person at cutting straight lines in 1 1/2 inch pink insulation foam. I was wondering what you would all recommend to fill in the gaps between my foam base and the facia? Would expandable foam help fill in the gaps, and if so, what types would you recommend? 

Edit: I should add that I'm using the score and snap method to cut the foam.

Thanks!

[Chris333]

I use Sculptamold to fill in that area.

[wazzou]

I don't know how big of gaps you're talking about, but I would maybe use some wadded up paper to fill the gaps and Sculptamold on top of that.
That expandable foam is pretty hard to control with how much to squirt in a gap and before you know it, your fascia is all wavy and buckled due to the force of too much foam putting pressure on it.


Chris just beat me.

[btrain]

I don't know how big of gaps you're talking about, but I would maybe use some wadded up paper to fill the gaps and Sculptamold on top of that.
That expandable foam is pretty hard to control with how much to squirt in a gap and before you know it, your fascia is all wavy and buckled due to the force of too much foam putting pressure on it.


Chris just beat me.

Thank you guys, it's probably any where from 1/4" to 1 1/2" of a gap.

[C855B]

That's a lot of gap, which you won't be able to manage with Sculptamold. Use the low-expansion foam, designated "Windows and Doors". Make sure there's enough gap to expand out of the gap and not put a lot of pressure on the fascia. DO NOT attempt to trowel or use a putty knife to control the just-applied foam, that's just a huge mess waiting to bite you. Wait until the foam is fully dry and then trim. Use masking tape and other masking over anything you don't want foam to stick to, such as the front of the fascia.

[mu26aeh]

At 1 1/2", I'd be cutting in a filler piece of foam.  Then you can fill with sculptamold etc

[MichaelWinicki]

I use Sculptamold to fill in that area.

This.

[Maletrain]

Expandable foam is VERY sticky.  And, it expands more than you think it is going to expand.  So, it tends to get into and onto things that you did not intend for it to touch, and then you can't get those surfaces clean.  It will also get into seams and then expand enough to push the surfaces apart.  I would not want to try using it anywhere on a layout. 

Sticking strips of just about anything into the open cracks and then covering them with the paper mache type ground material mix seems like a reasonable way to make a neat surface right up to your facia board that can be made to match your other terrain.

[pdx1955]

In addition to the above (general uncontrollability, etc) the foam can be pretty hard to carve - much more than the regular pink foam board. Rasping it ends up with a fine yellow dust everywhere. I did it once for some fill slopes on a past layout --never again.

For big gaps you could always use a couple layers of plaster-impregnated gauze to span them - that's a fast and easy fix.

[peteski]

At 1 1/2", I'd be cutting in a filler piece of foam.  Then you can fill with sculptamold etc

That seems like the most  reasonable solution.

Btrain:  a hot wire foam cutting tool makes shaping/cutting small or thin pieces really easy.

[nkalanaga]

Duct tape on the bottom to seal the hole, fill the gap with cardboard, and add a thick layer of scenery.  I've done that a few places, along with foam fillers and latex caulking. 

DO NOT use the expanding foam.  I did, and all I got was a horrible mess.

[OldEastRR]

Expanding foam also may keep expanding over time, especially if applied at cool temps and then the summer comes.

[GaryHinshaw]

Edit: I should add that I'm using the score and snap method to cut the foam.

You should check out these sabre saw blades for cutting foam.  They changed my life.   Some examples starting here.

[btrain]

You should check out these sabre saw blades for cutting foam.  They changed my life.   Some examples starting here.

Nice! Thank you for the advice everybody!

[Sokramiketes]

I guess I'm in the minority, but I like using the expanding foam in this area.  It bonds well to both the foam and the fascia, and seems less prone to cracking and separating in the future than other hard shell methods.