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Discussion Starter #1
I sometimes need to attach things to foam. In one instance it was a foam tombstone that I needed to attach to a thin plywood base, so it would stand up on a stage. Many years ago, I recall seeing someone use what I thought were drywall screws. But, that didn't hold at all on the polystyrene extruded foam board, I used for the tombstones. As I recall, what I saw many years ago was beaded EPS foam. So, perhaps that was the difference, but I didn't have any EPS foam on hand to test.

Perhaps there is a type of screw that has wider threads that would hold the foam better. Can anyone advise?

-Joe
 

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I don't know of any screw that would work with foam. For gluing something like a plywood base to foam I would suggest Gorilla glue or the Loctite PL300 foamboard adhesive.
 

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I don't know of any screw that would work with foam. For gluing something like a plywood base to foam I would suggest Gorilla glue or the Loctite PL300 foamboard adhesive.
^^^^ This

Use glue. I always use Gorilla Glue to bond pieces of foam together, or bond things to a piece of foam. I saw a video, or maybe a thread here, I don't quite remember, where someone used a screw with a washer on it to attach foam to things. I think that's as close as you will get using that approach, but I think you will also just end up with bigger holes when it inevitably fails.
 

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It isn't the screws, it's the foam itself. It has no structural strength to speak of. Glue over as wide an area as possible & I've used wire (like coat hanger or welding rod) To help support it. If it's likely to get bumped the glue will just tear the foam anyway.
 

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Discussion Starter #5
As I continued my research, I happened on this video in German. It seems to be the kind of product I am looking for, but I am not certain what they are screwing into.

They are drilling through a thin, hard surface with a paddle drill, and then the rest seems to be foam. So, perhaps this is EPS foam insulation, with a concrete skin on it.

their catalog with their foam anchors.
https://www.tox.de/downloads/katalog_2019_2020/TOX_2019_2020_Daemmstoff.pdf

I tried to find a U.S. source that might have similar products. But, I have not been able to find it. These kinds of anchors are perhaps only used in countries that have stricter building insulation requirements.

-Joe
 

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I found something like above for you.
 

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Discussion Starter #7
I found something like above for you.
Thank you for that link. However, we have tried the drywall fasteners, and found that they have very little resistance to any force trying to pull them out of the foam. The ones from Tox, that I linked in an earlier message will provide up to a 14 Lbs of force when trying to pull them out. They have a 5/8" Diameter thread, so I think that is a key part of why they have more force than the typical drywall anchor.

I will contact one of the German company's distributors, to see if any U.S. stores carry them. Or just settle for ordering from out of the country. I will report back my findings.

-Joe
 

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Thank you for that link. However, we have tried the drywall fasteners, and found that they have very little resistance to any force trying to pull them out of the foam. The ones from Tox, that I linked in an earlier message will provide up to a 14 Lbs of force when trying to pull them out. They have a 5/8" Diameter thread, so I think that is a key part of why they have more force than the typical drywall anchor.

I will contact one of the German company's distributors, to see if any U.S. stores carry them. Or just settle for ordering from out of the country. I will report back my findings.

-Joe

Are these similar ???



These will probably still rip right out of eps and xps foam because I think the foam is the issue not the fastener. Just use glue on a proper backing and make your life easier.
 

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I would glue a plywood back on the tombstone with white wood glue (so it doesn't melt the foam like certain glues would do) or spray on foam (used as the glue) between the tombstone and plywood and use something to weigh the plywood down to the foam until it dries so whatever you use has a tight fit with minimal gaps....Make sure you lay down plastic to capture any ooze to protect the surface it's sitting on....Then you'll have a nice plywood back to screw into and it will be enough glued area to hold securely to the foam plus the foam will be stronger having a plywood back....I'd paint the plywood black to hide it in the dark.....ZR
 

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Discussion Starter #10
Are these similar ???
Yes, those are the ones I am hoping to use. Though I wonder how I managed to come across them. They describe them as, "Dowels for Rigid Foam Plates". I am guessing that historically, wood dowels were glued into foam to provide a place to attach a wood screw, and that term continued to be used even though it is now a plastic screw. Their term "foam plate" is what in the U.S. is called "foam board".

I realize that other solutions may provide more strength. But, this is for an industrial application, where many would be used. So, the ease of application is important. For my tombstones on stage, I had already attached wood bases to the ones I thought needed it. But, I hadn't anticipated actors walking close enough to the tombs, that clothing may brush against them. So, a few needed additional support. I improvised by finding a piece of luan wood, that was approximately the right size. I used hot-melt (Low temperature) glue, plus some 4" wood screws. It came apart at a dress rehearsal, so the next time I put while glue on the wood screws, and more of the hot glue on the foam, and then that did the trick.

-Joe
 

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I have used the anchors listed above. They work pretty good. If you put some Gorilla glue or Loctite on the threads and then screw it into the foam board it will hold pretty well. Just be very careful when screwing the metal screw into the plastic anchor. I like to screw it in a few times before I attach it to the foam so it loosens up the internal threads a little. I have used it to secure my foam tops to my wood cemetery columns.

092097253506.jpg
 

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Plasti-Grip washers by Rodenhouse Fasteners seem to be the go to in the insulation industry. There's a masonry plastic one that looks like a flatter profile but not sure you'd want to try using with wood frame and the price doubles. Finding a source that will just sell you a small amount will probably be the challenge. Rodenhouse says the smallest amount sold is 250.

Home Depot has these:


As for the dimensions, Rodenhouse posted this: "The washer is 1.75" dia. and is about 1/8" thick, with the prongs that adds roughly another 3/8"."



Here's a video showing the product versions:

 
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