Roadbed

Screws hold poorly in insulation board.   With a prior layout I used Woodland Scenics Foam Tack Glue both for the roadbed and the track.   I worked well with Gargraves sectional track.  If you can pre-bend flextrack such that it holds its curve by itself, you can glue it as well.  Others have used a pair of zip ties to hold down track.  One zip pushed through the hole in the tie and another zip from under the layout securing it.

Bob

I am in your position exactly. But I ran across a video where the builder Gorilla-glued ribbed plastic drywall anchors into the foam where he wanted to screw the track down. I am using Gargraves #4 screws (the ones GarGaves sells) but I was unable to find drywall anchors that small. So I tested #6 drywall anchors and they work just fine. So I drill a hole in the tie where I want the screws (or preferably use an existing hole). Then I lift up the track, push some gorilla glue into the hole, and then push the drywall anchor in after it. Then I lay the track back down and Start the screws through the tie holes into the drywall anchors and make sure I haven't screwed up somewhere (pun!). Lastly, I put a weight or weights on the track while the glue is drying because it expands while it dries (see last pic!) so if I have overdone the glue it might tend to push the track up without the weight. Then the next day, I run the screws the rest of the way in. This method holds great in foam. But I am careful not to overtighten the screws--the track will be ballasted and the ballast glue will old it down tight enough. There is no reason to be grinding on the screwdriver. In fact, the screws can probably be removed once the ballast is dry.

Don Merz

PS: I did a layout with homasote. Ever since then I have wondered if that was when my respiratory problems started. If you do use homasote, wear a mask while doing anything to it. But I can't bear all that dust and I see no reason not to use foam.

Don Merz

Coarse thread drywall screws will hold in foam board.  Not the white stuff, but the pink or blue stuff that's denser.  If you turn the screw in slowly, by hand, and stop when the head just hits the tie, they will grab nicely.  You will need to use many more screws.  This will give maximum holding power as opposed to just a few screws.  

It's kind of like metal vs wood studs.  Metal studs, before they are assembled into a wall, are flimsy.  However, once assembled and covered with drywall, the entire system is very robust.  

Just my opinion but, there is no way that screws will hold in foam/insulation board. Just use TightBond Professional Wood Glue, and be done with it. Our whole layout is done that way, i.e. vinyl roadbed glued to the 3/4" plywood top, and then the Atlas track was glued to the vinyl road bed. Nice and quiet too.

If you are using sectional track use HOT WATER's method, if using Gargraves flex track you'l need screws or nails into something stronger than foam.   

Thanks everyone.  I got ahold of a handful of every type of screw and fastener combination I thought could possibly do the job from work today.  Im going to try a few combinations and see what happens.  I really don't want to use any type of adhesive if i don't have to.  If i ever go the route and change my track plan or add a switch here or there I figure it would be less hassle and mess.  Has anyone ever tried or thought of running a long screw (6/32 or smaller) through everything and putting a nut and washer on underneath?

The surface of my layout is extruded pink foam (5 inches thick on top of 1/2-inch birch plywood. I glue O gauge cork to the foam with yellow carpenter's glue and use Atlas O track screws to fasten the track to the cork roadbed. The screws are held well by the cork and can be permanently secured if epoxy is applied to the screw threads, although I did not find this necessary. Ballast to be applied when the rest of the layout is finished. I used layers of foam to elevate the track above the lower-lying terrain of a valley and a river. Additional layers of foam were used to create terrain above the track level.

MELGAR

My layout is all pink Styrofoam over 1"x4" pine. I used low temp hot glue under the AC Gilbert rubber road bed. This holds well, but must be held tight by hand for a few seconds while hot glue sets. On other sections I used the carpenters yellow glue, that also holds well but takes longe to set that the hot glue. I guess it depends how fast you want to move along.

Ray