Floor thickness question, sandwich floor will 3/8 ply work?

[KCStudly]

I have been using 3/4 and 1-1/2 thick blue foam, and to a lesser degree some 1 inch pink, none of which seem to have the film. The 1-1/2 inch is what they call "score board" which is partially slitted at common stud frame intervals, so that probably explains why this particular product doesn't have the film.

I will speculate that the thicker stock sizes and denser varieties of foam are inherently more sturdy during transportation and handling, so maybe that is why some products (maybe thinner and less dense ratings?) get the film and others don't. It may also be a manufacturing issue where they need more support until the product sets up coming off of the extruder. My guess is that the weaker stock needs the film to help keep it intact through to installation.

[daveesl77]

That makes sense with the thickness issue. I had to get the 1/2 boards and then glued them into 1" thickness

[roymeo]

I'm glad to see this stuff still seems to be available.

We started looking in Oakland and SF (Home Depot, Lowes, Building Resource Supply) and have only been seeing the white-foam-ball board. The guy I asked at the non-chain didn't even know what I was talking about (but he did seem more stock-boy than expert).

roymeo

[bobhenry]

With Dow Corning ( the blue foam folks) the " R " series foam is a bit more because of that membrane. It is essentially building wrap. A water proof and air infiltration proof membrane that is added for just that reason. The 3 thicknesses we have used on homes have been 1/2" 3/4" and 1 " I am sure there are a few other thicknesses available. It is truly amazing just how much strength is added to the foam board by that little stretchy membrane.

And back to the original question 3/8 plywood will work as a floor if the trailer is offering several intermediate cross members.

[dales133]

I've used dow blue foam on mine in 25mm or 1 inch and 35mm inch 1/2 and neither have had the film but as said before maybe it has something to do with the thickness.
The stuff I got has shallow kerf about 1 inch apart in one side
And I used the 35mm foam for the floor with 1/2 inch ply on top.it has cross members about every 400mm