The plywood would be a filler or basically a shim then? Unless you're looking for it to be structural it "should" be fine. Remember plywood on the flat has zero structural or supportive properties.

@millowrkman. I am not sure how to answer your question. I thought we would first apply the plywood and then use shims on top of the plywood should we need to level anything for the granite.

Again as long as you are not looking for it to support the granite it should be fine. If it is supporting the granite it is a no go as plywood on the flat has no real structural integrity.

"plywood on the flat has zero structural or supportive properties."

re. "supportive properties"; is it your opinion that the plywood would not work to increase the height of the countertop?

Again are you looking at it strictly to raise the height or are you using it to support the granite? If you are looking for the strength of the plywood to support the granite, no.

We would just be using the plywood to raise the height. The cabinets and the shims will be doing the work of supporting and leveling for the granite.

What happens to the edge of the granite? It is a laminated edge or a mitered edge?

Depending on the edge and its height, the plywood might be visible.

Here is a 2 cm slab with laminated edge and plywood placed above cabinets. It was designed this way, typical installation for 2 cm slabs in CA.

Adding any more height would make that plywood underlayment visible.

You might have been better off raising the base cabinets and doing a taller toe-kick.

@chispa .We will have only one cabinet exposed like the one you have pictured. I ordered skins and I will install the skin so it covers up the plywood edge on this side. The plywood will be precisely cut to sit flush with the base cabinets. We have full overlay doors/ drawers that can be adjusted upwards so that the plywood will not be visible in the front. I was actually going to get some wood filler and fill in the spaces of the plywood, then sand, prime & paint to match the cabinets so it will make any tiny sight of the plywood blend with the cabinets.

You have a second thread on what seems to be the same question.

https://www.houzz.com/discussions/6513513/question-on-diy-reinstallation-of-granite#n=1

It's best for everyone to keep everything in one spot.

I have no idea what you are trying, or intend to do.

You have provided too much information.

Try to simplify. For example.

Our lower cabinets are installed. We are reusing the granite tops, but want to raise them 1/4". What do I use to shim them up and how to best attach the shims and tops.

chispa's comment re: an issue with seeing the plywood is exactly what I was thinking while reading your post. If you were putting in new countertops, you would be able to change the edge in order to make sure that the added plywood is covered. However, since you are reinstalling your existing countertops, there may be an issue with the plywood being visible.

I also was wondering why you couldn't raise the lower cabinets by it under the cabinets + just installing a taller toe kick as chispa has also wondered about in her comment above.

@PPF. One post asks if this can be done and the other post requests instructions on the best way to do it. The other post is asking more specific installation questions. I think I have concluded that this can be done, so I moved on and my other post focuses on how to correctly re-install the granite over the plywood.

@dani_m08. I can't raise the base cabinets because then I would have to raise the pantry to get the lower doors to line up and then the upper door of the pantry would not line up.

The problems stems from the fact that our old cabinets that were called 42" uppers were actually 41-1/2" cabinets. We kept the same layout and our new uppers are 42". We hung them at the same height as the old cabinets, not realizing that the old cabinets were 41-1/2" tall. So then the pantry sticks up 1/2" above the uppers and the doors do not align.

Plywood is a thickness compensator for a 2 cm stone with a 4 cm built up edge. It's not used with 3 cm. 3cm goes straight on the cabinets, with shims to level.

@jlcorp - I forgot about your panty issue.

I know that you've noted in your post that you like the way your uppers look (even though they were installed too low). HOWEVER - it seems like it might be easier to just raise the uppers to where they should have been installed vs. trying to figure out ways to make the mistake work.

I'd place your shims on the upright portions of the cabinets where they are supported vs just where the plywood is - as the plywood is likely to just deflect. But basically using the ply as an extension of the cabinet sides is fine -it's like a big flat shim

No, my photo was not to show the exposed side of a cabinet, which was being covered by the range in that kitchen, but to show you that raising the counters would expose the plywood along the front of your cabinet installation.

Sure you can try and cover it up and paint it, but that is the MacGyver solution and not the proper/elegant solution.