2" Beadboard (Expanded Polystyrene) ok for walls?

[Johnny Swank]

No chance of getting anything more than 3/4" pink or blue insulation board around here without doing a special order. I think I saw someone using 2" beadboard for their walls on here somewhere. Would that still be OK, or would I be better off gluing 2 sheet's of 3/4" pink insulation board together instead. I've already bought a couple sheets of the 2", but I'm not getting a warm fuzzy thinking about how friable those things are, especially when you try and sand them.

For that matter, is a 1.5" wall going to be thick enough if I go that route? I really need to pull the trigger one way or another in the next couple of days in order to finish this in a decent time frame.

[GPW]

Swank , I’m using 3” beadboard for mine ... same density as the Blu or pink ... No problem and much cheaper ...

[Johnny Swank]

That's my problem, this isn't as dense. It just doesn't seem nearly as burly as the pink or blue foam, and I've got some real concerns about cutting out doors and sanding. I'm going to make some calls today and try and track down some 2" foam, but if that falls through I'm going to laminate the 3/4" sheets together and plan on using spars and likely a couple of 1x3 boards on the inside from front to back. I need the hard points anyway, so it'll knock out two birds with one stone.

[GPW]

Try checking metal roofing companies , concrete foundation companies , lumberyards that supply contractors ...... just an alternative to the somewhat disappointing HD or L’s (box stores) ... For using less dense beadboard , just make it thicker .... Twice as thick is 8 times as strong ...

Sanding , beadboard usually sands best in only direction , two way (back and forth) pulls out the beads ... the less dense it is, the more pronounced the problem ... The only way to really find out is to sand a "test sample" ...

[ghcoe]

Found this on a web site, not sure if I would go with it since it does not recommend it for wet conditions.

Expanded Polystrene
Expanded polystrene is much softer and lighter than extruded polystrene and is much less durable. Its advantage however is in its flexibility and plasticity. Expanded polystrene is easy to shape and mold into a variety of shapes, and therefore is commonly used with stucco for interior walls where insulation is not an issue, but customized forms are. Expanded polystrene does not hold up to wet conditions well and should not be used under exterior walls in areas with extreme winters.

http://www.ehow.com/info_8699357_kind-f ... tucco.html

[atahoekid]

If you decide to glue the sheets together, I think you'll find 1 1/2 inches will be plenty thick and very nicely insulated

[crttaz]

In Ohio it is easy to find pink foam at HD, blue at Lowes.

I use the pink for lining shipping containers for transmissions.

1.5" works perfectly.

[GPW]

Remember , foams come in different densities ... not all foams are the same ... Here, HD or L doesn’t carry the thicker extruded foams , for some stupid reason ... Won’t order it for you , unless you want a whole pallet and still want retail (per sheet) prices for the foam even if you do get the large quantity ... Something Not right about that eh ? A fact confirmed by my roofers who use pallets of the same foam , and for ~ 10USD a sheet in quantity.... (what I was told ) Another reason to shop around and Not rely on the Box stores ...
For my FoamStream , we’re using the 2lb./cu.ft. Beadboard , and yes it will absorb a little water over time if left out in the rain , (the spaces between the beads ) but covering will protect it ... Even with water intrusion , it still won’t Rot , should that happen somehow (?) ... When I got my beadboard blocks , they had been left out in the rain and were damp , but after a few days inside the studio , they’re now as dry as toast ... no problem ... and a little Lighter too ..
I’ve been making foam wings for planes for many years , and never had a problem , even uncovered ... But I have seen houses with that Foam/Stucco thing , and that doesn’t seem to work very good outside ... Once the stucco cracks , water gets in and affects the stucco to foam bond .... Stucco flakes off .... water intrudes further to the woof framing behind , with predictable results ... Could be just the quality of the construction and application technique that is left wanting ... ? We’ve seen a LOT of contractors take "short cuts" to expedite the job , and save more money for themselves ... Even good materials applied poorly aren’t quite as good as they are specified to be ...

[Wobbly Wheels]

I used it in the sandwich for my floor. I won't do that again because it's far too compressible for my liking. I don't think I'd use it for walls either because of the sanding thing. I'd laminate blue or pink to the thickness I need, but that's JMHO.

[GPW]

W2, most of the bead board we’ve found is 1lb./ cu.ft. (as used for model plane wings ) Is that what was on your floor sandwich ?

[Wobbly Wheels]

PNot sure what the density is, but it's Korolite type 2 rated @ 20 psi and a (derated) bouyancy of 55 lbs/ cu ft. I called the rep and asked for the density in lbs/ cu ft and he was baffled...

Pretty sure this stuff was 1 lb. If I remember, I'll look it up later (I'm on my phone, at work) and edit it into this post.

It was also covered with 1/8 luan and 6 oz glass. That would have been enough had I used pink or blue.
Woulda, shoulda, coulda... and next time I will!

[GPW]

A little squeeze will determine the density ... the lighter stuff squeezes pretty easy , the heavier , not so much ...

[Wobbly Wheels]

Exactly: that's the problem. I've 'squeezed' just it by walking on it. Because it's so easily deformed (unlike pink or blue), I wouldn't use it as coring because that's exactly what coring needs to withstand.
Again, I'm not saying that no one should...only that it was the wrong choice for my application.

[GPW]

Quote : “ we should encourage free thinking... “

[Wobbly Wheels]

Absolutely!
And if our collective experiences can provide insight for someone making a decision, then even better.