Australian EPS weight variations

My first EPS core was from VH grade which is rated at 1.75 lb/cuft, but actually was much heavier at around 2.25 lb/cuft (36kg/cum)

I want close to a #1.5 core for the four I’m cutting next week, which means a grade or two down from the VH. M grade is rated 1.125 (18kg/cum), but my supplier says the weight can vary a bit and it’s more likely that the delivered blocks will come in at 1.4 (22kg/cum). I’m happy with 1.4 lb/cuft, but start to get concerned at 1.1 lb/cuft, because I’d hate to end up vaccuuming a “wafer thin mint”

Do you (infinitely more experienced - as everyone here is) guys have any input on how much weight variation to expect in EPS blocks?

Is variation always heavier than spec? (I guess in many applications heavier is good, but lighter is cheating, so suppliers err on the side of good?)

I appreciate any input.


Red Boards- I’ve ordered several batches of styro from the same company here in WA over the last few years and found that there is noticeable variation in weight and compression strength with each batch. I’ve always used M grade which by my calculations does work out to what is commonly referred to in this forum as 1.1lb for both sandwiched sailboards and non sandwiched surfboards. The most noticeable variations occured with the sailboards because of both the amount of material being used and the extreme punishment they are exposed to. Most styrofoam manufacturers here in Australia are not really making their foam for use in the surfing industry so, although some quality control must surely exist, I doubt it is as exacting as that found in the blank building industry. If you are using the 18 kg foam for surfboards that are not sandwiched then 2x 6 on bottom and 3 x6 on top will hold together quite well but not be really light. 2x5 bottom and 3x5 deck is much lighter but definiely not as durable. Good luck.

Hey Red,

Yeah, the Aust. or American categorization of EPS densities are different.

I think its C - L - SL - M - H - VH…

I work with SL for Composite boards…and thats aparrently a smidge lighter than the US “1lb”. SL would’nt be hard enough for straight-out glass job.

All the stuff in Victoria basically comes from one blower. “RMax”, with other suppliers just buying their blocks and slicing it.


Great info,

Thanks Kenton and Josh.

Takes a breath and goes for it…

I, like speedneedle, use the SL grade EPS for sandwich boards. I’ve found the M grade just ends up that bit too heavy.

But without skins as a straight glass job the M grade feels a bit too soft.

SL is pretty cheap as well.

The only thing you have to watch is that you dont squash it in the bag.