Using extruded foam board and screwing down track

Screwing to the wood will transfer more sound through the foam, to the wood, via screws being a solid link. I am going with short track screws into the foam only, and some caulk as adhesive here and there, will help too. I have no doubt this method will be strong enough.

I have fasTrack and i found that the trim screws that are sold in the same section as regular drywall screws are a perfict fit.  I found two differnt lengths.  Both worked well in the foam to hold the track in place.

I used Woodland Scenics cement to hold Atlas track in place. It has held well for over six years in a non-climate controlled environment. 

Bob

Ok, I didn't think it would fasten into it. Great news. Maybe I'll get them long enough to bite well into the foam depending on the depth.  Thanks for the tips.  How about the clear adhesive caulk?  I use that on my crown moulding and baseboard to fill the gaps and it adheres well.  I am going to test the screws and a few dabs of the adhesive caulk on a piece of foam.   Much appreciated guys!   I'll post up pics when I get around to starting it.  November!

You just need screws long enough to go deep into the foam but not to the plywood underneath. Dipping them in white glue will glue them in place. Remember, you're really trying to keep the track horizontally positioned -- not necessarily holding it down.

Some forum members drill a hole and use wire ties, zip ties or cable ties. One end through with the head in the screw depression in the track and another one underneath with the head attached. Pull snug, but not too tight. You don't need to do every piece of track.

The 4" length usually has a small head and narrow thickness. 

I worry about shifting, not gonna turn it upside down often.  The screws are acting like dowel posts. The vertical hold is a bonus. Testing of any adhesive on smooth and roughened surfaces of a piece of scrap foam, would be a good idea. Watch for chemical melting of the foam, pull to test holding power on smooth & rough areas    

A coat of brushed on latex primer on foam can help protect foam from reacting with other paints/adhesives too. 

My basement layout is all MTH Real Trax, and it expands and contracts so don't hard mount every section. Go easy on the switches as you do not want to induce bending stresses into these.

If I were building a new layout, the sectional track would be glued to the foam with a cement that dries flexible, perhaps Liquid Nails.

Remove the poly film [skin] from the foam before applying glue or paint. The best way to stabilize the track over foam is to ballast it, applied with simple 50/50 white glue/wet water mix.

As for gluing track to foam, Liquid nails makes a foam compatible glue.

I use Liquid Nails to secure the pink foam. Dewey is spot-on about removing the protective film. For paint, I use flat latex house paints and craft store acrylics.

Gilly

I used a spot of hot melt glue about every 12".  My entire layout is 2' rigid foam board over 1x4 framing.  No plywood was used.

I used a product from Home Depot to cover all the foam boards and then put a skim coat of Gyposlite on top. Once it was dry I painted it and layed the track on top.  I used drywall trim screws to hold the track in place.  I found two differnt lengths and the diameter of the screw is very close to the hole in the track.  All the screw does is hold the track in place.  This is the roll of material from Home Depot.  BOEN 36 in. x 75 ft. Self-Adhesive Fiberglass Drywall Joint Tape Mesh FM-3675

I would suggest glue instead of relying on screws if your engine is heavy.  As the engine goes around the curves, it imparts a force tangent to the curve itself that will, in time, possibly pull up any screw in that area.  One thing that could be done is to drill the hole, remove the track section, push some glue or caulk into the hole and insert a small plastic expansion sleeve.  After replacing the track section, insert the screw into the sleeve and tighten.  As you screw it down, the bottom of the sleeve will flare out gripping the foam.  Since the sleeve is plastic and smooth, any glue or caulk surrounding it will make a tighter seal than just inserting a bare screw.  A bare screw will twist around as you tighten it and there's no telling how the glue or caulk inside the hole will wrap around the metal threads and contact the foam.  An expansion sleeve will grasp the foam much more evenly for a better bond.  As you screw down and the bottom flares out, it will press the glue or caulk into the sides of the foam with less chance of pulling out.  This is the same technique as if you were placing a screw into drywall to affix something on the wall.  A screw can rip out of drywall, but the expansion sleeve holds everything in place.....good luck! 

I use 3/4 plywood 2 inch pink foam with Fastrack  a 12 x 24 layout and no screws or anything to hold track.  Layout is 4 years old and no track movement.