working with foam board?


Anyone have any experience with this stuff? I'm trying to replace the old scuttle panel for access to my attic with a contraption that I am trying to make out of some 2" (thickest I could find) foam board and Masonite. Reason for doing this is that my bedroom closet gets very cold in the winter, I ASSume because the ceiling is well insulated but the panel is just very thin plywood. 2 questions:
1) It appears that in an effort to make a tight fit, I cut the foam board just a little big. Is there an easy way to shave it down a little? It doesn't "shave" well with a knife. Am thinking Surform file? Or will that just make a mess?
2) What do you use to glue it? I'm trying to laminate three pieces together for better insulation (the bottom most piece will be hanging; I cut it slightly smaller so it'll fit in the "jamb" area of the scuttle hole. That one will be faced with Masonite for a finished appearance.) construction adhesive isn't doing it (I put 8-10 dots on there.) Should I just use more construction adhesive, or is there something better?
thanks
nate
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On 01/01/10 05:21 pm, Nate Nagel wrote:

Not even with a "Stanley knife" with a new blade?

I've used "foamboard adhesive" in cartridges designed for a caulk gun. Don't recall the brand.
Perce
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wrote:

A four inch batt of insulation on top of the scuttle would seem easier, imo.
pic:
http://www.diyhomeinsulation.com/images/scuttle_hole_cover.gif
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And if you get paper faced it can be glued right to the scuttle.
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On 1/1/2010 17:21, Nate Nagel wrote:

It shaves if you use a good sharp blade. I built what is essentially a box with one side missing to insulate our pull down attic stairway and used good quality foil duct tape to assemble it.
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George wrote:

I just have a scuttle hole in the hall- after I had 8 inches of loose-fill insulation added to attic, I built a dam around the topside of scuttle hole out of 1x8 (including a place to park my butt as I climb off top step of ladder), so as to not get avalanches every time I opened the attic. I then cut 2 sheets of 3/4" foamboard and taped them together, to lay inside the dam I built, as I climb down. I also taped a sheet of foamboard to the top of the finished lid that sits in trim on hallway ceiling. This gives me about a 6" dead air space between the layers of foamboard. You want the bottom lid to be a tight fit in the hole, sort of like a cork in a bottle. I added a handle facing down into the hall, so I could pull the lid down tight. It is a bit of a juggling act getting it all closed up, but it works. Not a real good job- this was just a quick and dirty with stuff I had laying around. But it does make a noticeable difference. One of these days I need to redo it with better foamboard, trimmed more carefully. Maybe, instead of a drop-in upper lid, one with 2 layers of 2" thick foamboard glued or bolted together with a rabbited edge that fits the wood dam tightly, and a handle on the bottom to pull it snug, like the lid below it. I raked the insulation up against the dam I built, but another layer of foamboard on the outside of dam, down to the buried attic floor, would probably help.
-- aem sends....
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wrote:

Cut easily on a table saw if you have one, or even with portable circular saw (although may take a pass from each side). Surform will work and will make a mess.
Use foam board adhesive. Regular construction adhesive will often dissolve the foam.
HTH,
Paul F.
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Get a couple of these. Just extend the blade to the thickness of the foam.
http://www.interiorone.com/admin/images/closeup_images/bk-1-l.jpg

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To cut it go to a hobby store. They have a little tool that looks similar to a coping saw except it has a wire (like a guitar string) and it takes a couple D batteries. The wire heats up and glides thru the foam. This little gizmo works great and is less than $10.
Believe it or not, elmers glue will work fine. Hobbyists use it for such applications. You can try 3M's 777 (triple 7). Try a test piece first. If it doesn't eat the foam, it would be better.
Hank
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On Fri, 01 Jan 2010 17:21:09 -0500, Nate Nagel wrote:

I've cut it with a blade designed for metal cutting in the jigsaw before; it doesn't generate a lot of mess.
A bit of resistance wire and a junk PC power supply should work too.

Hmm, never tried. Gorilla glue might work...
cheers
Jules
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Jules wrote:

eventual resolution - I took it out on the deck and used a belt sander to knock it down. Worked OK as long as I kept the sander at about a 45 degree angle to the board, otherwise it'd chatter.
Had a tube of PL premium that had been kicking around way too long, just used about half the tube, that seems to have done the trick
put half the plug in the scuttle hole overnight and it got down to about 20 degrees, when I popped it up to tidy up in the attic this AM the topside was cold as heck but the surface of the Masonite felt warm. That's a good sign. Was only two layers (R-20) whereas my final assembly will be 3 layers and should be about R-30 so hopefully this will solve the cold closet problem. (attic was probably colder than previously as well because 2 of 3 attic vents had birds' nests in them, which I removed and re-screened while I was up there.)
I did see the recommends to build an insulation dam around the opening, but I'm out of foam board so that'll have to wait for another day. Good idea though.
I also saw the post about using fiberglas batts, you have no idea how much I hate fiberglas insulation and how much nicer I find solid foam to be. Personal preference I guess.
nate
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Even better, I found a jigsaw blade that was essentially a knife - no teeth, just a sharp edge. That thing went through foam board like butter - I was using it for building concrete forms for countertop. I'm guessing the knife edge kept the cut smooth, and the friction from the blade moving heated it up enough to make it cut smoothly and not catch little bits like a standard razor blade will.
Henry
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that sounds like the ticket, if I have another project that requires foam board I'll keep an eye out for those.
The day I finished my scuttle plug, it got down to mid-teens that night (that's quite cold for this area) so I was happy to have done it! Bedroom closet stayed noticeably warmer, despite my having cleaned out the attic vents.
nate
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When this material was new, the favourite tool to cut it was an electric carving knife. The edges will always crumble, but the elec. carving knife can be held more steady than other tool, which reduces crumbling.
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Carlsbad Springs
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On Sat, 2 Jan 2010 15:46:30 -0500, "Don Phillipson"

See: "Sculpting with the Hot Wire Sculpting Tool" for foam.

http://www.youtube.com/watch?v=Pn9Jp9Bu-lA

An industrial type would be needed for cutting flexible urethane molding.
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Wood glue works well. Once I had a lot of it to cut and made a jig saw like contraption that used a hot wire to cut it. Device was powered by an old soldering gun.
Jimmie
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wrote:

You can cut foam cleanly with a bandsaw. Not sure which glue is best for foam.
I made a corregated cardboard box cover for my attic staircase and fastened a fiberglass batt on top using duct tape. It fits over the pull-down stairs. After several years the edge of the box began to fray so I glued a thin strip of pine around the edge. On the trap door itself, I put a sheet of styrofoam and protected that with thin hardboard (so the foam would not be damaged from shoe tips on the ladder. Not pretty, but it is lightweight, out-of-sight, and insulates well.
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