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Plywood recommended for under quartz countertop?

Tommy87 | Posted in Green Products and Materials on

I am helping my sister install her 3/4” quartz countertop this week. I bought 5/8” Cdx for the counter to sit on. She is complaining about the smell of the cdx and that she would like to use something without added formaldehyde because that’s what all her cabinets are .

What would you guys reccomend ? In your experience how long does it take for the smell of cdx (fir) to go away? Is cdx less toxic than other plywood boards ?

I could get some purebond plywood but they only make it 3/4” which I believe will be too thick.

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  1. user-2310254 | | #1

    The standard thickness for quartz is 1 1/4 inches. Has the 3/4 material already been fabricated? No doubt the standard material is more money, but the plywood adds cost as well.

  2. Expert Member
    Michael Maines | | #2

    I would recommend Advantech, which uses mostly isocyanate-based adhesives, rather than phenol-formaldehyde used in most CDX, so there is very little smell. Plus it's a very stiff and strong material.

  3. Tommy87 | | #3

    Steve, yes it has. In my area 3/4 seems to be most popular

  4. Tommy87 | | #4

    Gotcha. I will run it by her.

    Just for arguments on both sides, let’s say I went with cdx. How long does it take for the smell to go away?

    I also do believe I have some AFM Safecoat in my garage I never used which is supposed to block vocs. Has anyone ever used this ? Does it remove the odor as well?

  5. Tommy87 | | #5

    Hey guys, so my sister said for me to go ahead and use the cdx because it would of took weeks to get something else.

    I installed the counter and of course she is complaining about the formaldehyde smell. I tried putting a product called Lumber seal over it but it didn't do anything. I found another product called Safe Seal by AFM but they said the product will not work over an already applied water based coat.

    Any of you have any other ideas? Obviously the top side of the plywood cannot be sealed because the counter is over it.

    Side note- how long does this cdx stuff take to offgas? Even smells a bit strong to me..

  6. Expert Member
    Michael Maines | | #6

    This is a funny thread. "Hey, what should I use." "Use this." "I didn't use that, now what do I do."

    You could try coating the CDX with shellac or a shellac-based primer such as BIN or Kilz (both products have multiple formulations so you'll have to read the labels or talk to your paint rep). Your sister may not like the alcohol smell but it doesn't last long. Shellac can go over pretty much every other finish. I don't know how long the CDX smell will last.

  7. Tommy87 | | #7

    I know , pretty lame. I will give that a shot if it doesn't work she wants to remove the counter.

  8. Expert Member
    Michael Maines | | #8

    Naw, just giving you a hard time. As a designer I'm used to builders not quite following plans and then looking for advice on how to fix their work-arounds. Good luck!

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