I just scored some eps foam from a construction site. They were using it as insulation for the concrete floor of a new movie theatre. Is this the right stuff ? Is there a way to tell the weight, #1 or whatever ? -mv

cut (and stack, if necessary) the foam into a 1’x1’ square and weigh it.

1’x1’x1’ I think, thus the stacking suggestion

or so you don’t waste it, figure out how many cubic feet in the rectangle containing your plan shape and weigh that. i.e. if your making a 8’x22" cut a 8’x2’ rectangle and weigh it. Factor in your thickness and you have it.

you can measure it as suggested…

press down on it with your thumb…if it compresses easily and feels springy its proly #1…if it feels firmer, like a blue clark blank, then its closer to #2…for floors it might be #2…for wall insul then proly #1

I am assuming, if it’s #2 it will work, but will be a little heavier? Also assuming, the number refers to the weight i.e. a 1’x1’x1’ cube of #1 will weigh 1 pound.

Thanks for everyone’s input! -mv

good assumptions…

my std #2 eps shortie blank will weigh about 2.5lb shaped…same with a clark blue is about 3.75lb…slightly heavier glassing will still come in lighter than a std poopee, but will be stronger

The Lowes stuff I’m using seems less that 1lb the heavier the easier to work

Strength’s in the sandwich construction technique though

many many options on that…


I was just wondering, I can get my hands on some of those square blocks of EPS but needless to say they are not the right size. Can I just glue them together? What type of glue? And then hotwire? is it possible to put together two blocks to make it longer or is it only possible to make it thicker(strength wise)?

Any help would be great!


Polyurethane glue. Make ‘em as big as you want. Almost every board I’ve made is longer than 8’, so I do it every time.

Mike Eaton makes his Unlimited-class paddleboards out of 12’ pieces - glues to 16’, 18’, 19’, etc…with gorilla glue.

Glue up any two pieces of EPS with polyurethane glue. Clamp together with blue tape. Wait 4 hours. Break the piece apart. The EPS will fail, never the glue. The glue becomes the strongest part.

Edit: the other good things about foaming polyurethane glue: Planers go right through it like foam, while other glues make a harder spot that can make your planer skip or pull out chunks. And similarly, hotwires cut right through it, while hotwires don’t like to go through epoxy glue lines…


Great info. Can you recommend a brand of polyurethane glue ? Thanks! -mv

The Elmers poly glue is half the price of gorrilla glue and it does a great job. You can get it at Home Depot.

Check the parallel thread:



Well I have been looking around for some stuff now but it seems like the stuff I can find in the DIY stores is not very dense, is seems to be very fragile and is like compressed balls that cant be cut very precise, just tell me that that’s not the stuff, then I’ll go searching for some of the right stuff, but how dense should it be? I’m not sure we have those #1 #2 categories here in denmark.



Not very dense…check. Kind of fragile…check. Loose balls…check. You found it! :slight_smile:

Cut wide of your lines, or hotwire, and then you’ll be surprised at how smoooth & fair the shape gets with a planer, a surform, and then a big long (like 2’) sanding block.

One of the other threads right now - the one about the future - talks a bit about how lightweight EPS is really only there to take the place of air to make these things easier to build. Don’t count on it for much…

And welcome to the world of beer cooler foam!

I second what Benny is saying. I was surprised how nicely it cleaned up.

Try 36-40 grit instead of surform. Cuts much cleaner while the surform rips chunks out. See link for tools!


I am in the process of making one using the Lowes foam. The one mistake I made was using too much regular elmers “white” glue - it made hard ridges that made some of the final shaping difficult. Had to “spot” shape the ridges with a microplane which, if I didn’t ruin the lines, seemed to clean them up pretty good. I used a planer to rough out the shape, but mostly used a 36 grit sanding block. The 36 grit worked great. Blank cleaned up nice (especially after “sealing” the blank with DAP “fast & final”) - I was very surprised & grateful for all the info that these folks have posted.

One other thing I found made life more difficult - my stringer was two pieces of luan doorskin glued together with epoxy. Very hard (even with a razor sharp block plane) to keep the stringer down when shaping the eps. Hotwire or a friendlier stinger material should make that exercise easier.

Good luck - it is a blast!


I’ve checked the archives and found plenty of info on glassing schedules for #1, What are you using with your #2 eps ? -mv