Replies

1. Expert Member
   Michael Maines|Dec 19, 2020 12:34pm|#1

   Ryan, that's a common problem. You can hack away at the foam with a pry bar or similar. It's dense but breaks apart easily enough. Or you can drill through it with no trouble at all. It's very similar to polyiso rigid foam in composition, if you have experience working with that material.

2. Expert Member
   Zephyr7|Dec 19, 2020 01:48pm|#2

   For smaller holes (up to maybe 3/4" or so), drill bits go through easily, use auger bits like you'd use to bore holes in wood. Twist bits work too, but don't use spade bits because they tend to jam in the relatively soft foam.

   What I've done before for larger holes is to use hole saws. Drill with the hole saw until it bottoms out, then use an old beater screw driver to split the foam core and get the pieces out of the hole. Once you clear the first chunk, use the hole saw to drill deeper and repeat the process with an extension bit for the hole saw. It's a bit slow going, but it makes clean larger holes without any special equipment.

   I wouldn't worry about cutting holes in thick spray foam, it's not particularly difficult to do.

   Bill

1. 
   删除d|Dec 19, 2020 02:02pm|#3

   删除d

3. 
   Ryan Lewis - Zone 4A|Dec 19, 2020 02:02pm|#4

   好,好,好先w. I have much polyiso board, yes. I've heard that removing closed cell foam is extremely hard and a home inspector once said "powerful saws break."

   I guess he was misinformed?

1. Expert Member
   Zephyr7|Dec 20, 2020 01:03am|#6

   I would say he was, but with one possible exception: Depending on the type of foam, it might have melted and bound blades. That CAN be an issue. When cutting thick plastic materials, you have to be careful because the plastic material will melt from friction and then essentially immediately start to glue back to the blade, which can cause the saw to bind or otherwise bog down a LOT. Slower cutting speeds can help with that.

   I've going through spray foam before to make holes for pipes and wires, and it's never been a problem aside from taking some time. If I had to cut a BIG hole for something like a skylight, then I'd have to be more careful with the saw.

   Bill

4. 
   DCContrarian|Dec 19, 2020 06:31pm|#5

   The biggest problem I've found with foam is that sometimes you have to make a big hole to find what you're looking for.