Return to the Kitchens Forum | Post a Follow-Up

 o
Thickness of 2cm Countertop Underlayment (and Type of Material)

Posted by garhoo (My Page) on
Sun, Aug 10, 08 at 10:33

Hi all,

We are having 2cm countertops installed (w/ 4cm bullnose edges) on our new cabinets.

My contractor cut out the underlayment yesterday: 1/2 inch "floor underlayment" particle board. Everything I've read seems to indicate that plywood (preferably exterior grade) should be used rather than particle board. So I've decided to buy some plywood myself and cut it out as required.

Main question:

(1) Should I go with 1/2 inch or would 5/8 be better? (The latter makes more sense to me.)

Additional questions if there are any takers:

(2) Am I right in rejecting the particle board? (I just don't see how this can be cleanly screwed into or cut for the sink without crumbling -- indeed it's already crumbling on the edges.)

(3) We have a dishwasher gap to span (24"). At the moment there is just the underlayment going over it with no additional support. Should I be attaching a supporting piece to the wall rather than just spanning the gap with plywood & granite.

Thanks!


Follow-Up Postings:

 o
RE: Thickness of 2cm Countertop Underlayment (and Type of Materia

First, I would question the professionalism of your installer. Underlayment is not the same as industrial grade PB, that being said, MDF or plywood would be a much better choice, and yes, I would use 5/8" material rather than the 1/2". Especially if you have Euro cabinets you will run into problems. Spanning the DW area should not be a problem, just make sure they don't put a joint close to that area.
FYI Particle board comes in a number of different densities. This indicates how much wood and how much filler or adhesive is in the sheet. Industrial board is a 45 lb density, commerical board is 42 or less while some underlayment is less than 20 lb density. MDF is typically over 50lb density, and very stable, some are even exterior grade and water resistant.

A contractor that buys based on price at a box store, is, in my opinion, not a professional. Good Luck !


 o
RE: Thickness of 2cm Countertop Underlayment (and Type of Materia

We are also going to be installing 2 cm countertop and the installer told us we could save money by installing the subtop ourselves. He told us to use 5/8" plywood. Then at Home Depot we decided to ask for an estimate there and he basically told us that we have to order a expensive edge (not the standard basic edge) because you will be able to see the 5/8" plywood. So I imagine that 1/2" would be even harder to hide. I guess I have questions now too...so is anyone ever able to order the standard basic eased edge? Does the countertop have to be thinner to not require a subtop?


 o
RE: Thickness of 2cm Countertop Underlayment (and Type of Materia

We will also have 2cm granite (being installed tomorrow). I don't know what is necessary or customary. I can only tell you that my contractor installed 3/4'' plywood. Our dishwasher is at the end of a run, so there is a wall directly to the left of it. My contractor attached a supporting piece of wood to the wall next to the dishwasher and also behind the dishwasher.

When my granite installer came out to template, he did comment on what a good job my contractor had done.

Who is installing your granite? Maybe you could call them and ask them what they recommend?


 o
RE: Thickness of 2cm Countertop Underlayment (and Type of Materia

We used 3/4" plywood for a couple of reasons: We needed clearance for the top of the drawers, etc. We have a thick edge on our granite (dupont with square offset) and needed a thicker plywood due to the edge. We used A grade plywood, just because CDX and others had lots of knots, etc that I was worried about. The cost was not too much more. My granite installer said it was perfect, so I gues we picked the right thing!


 o
RE: Thickness of 2cm Countertop Underlayment (and Type of Materia

Hi Tom,

Thanks for your answer. I don't know the density of the PB, it doesn't mention that on its printed side. I shall definitely opt for plywood then.

FWIW - my contractor assured me his decision wasn't based on price--otherwise he would have gone with OSB--and that this is recommended practise. I just haven't seen it recommended anywhere! :(

Thanks again.


 o
RE: Thickness of 2cm Countertop Underlayment (2)

Thanks for all the answers. You all seem to be having a good experiences with your installers!

I don't know my granite installer unfortunately. He is provided by my contractor and therefore I can't check with him. I already have one (small) piece of granite on a corner piece and I've tried it with 1/2" -- the drawers don't hit the edge, but they're pretty close. 5/6" will give me a tiny exposed line of plywood but not much. You can't see it unless you're on your knees so it's worth going 5/8" I would think for the strength benefits.


 o
RE: Thickness of 2cm Countertop Underlayment (and Type of Materia

Here's what's worked for me over the last 23 years;

5/8" ACX plwood as the subtops......

I'd use a wall cleat behind the D/W, and I prefer to NOT have a seam over the dishwasher.

As far as MDF or Particleboard for subtops - I've seen more failures from the mdf/particle board swelling up when it gets wet - it swells up and breaks the stone. Seen it way too much - so ACX PLYWOOD is what I use everytime.

Hope that helps

Kevin


 o
RE: Thickness of 2cm Countertop Underlayment (4)

Kevin - that's great. I really appreciate your advice.
Thanks


 o
RE: Thickness of 2cm Countertop Underlayment (and Type of Materia

Here's what we did under our 2cm granite...
1) they recommended 5/8in plywood, said if we used 3/4 it MIGHT show.
2) DH INSISTED on using 3/4 plywood because he didn't think 5/8 would be strong enough esp with our overhang (we also have corbels)
3) We installed the 3/4 against all advice.
4) granite went in and NOTHING shows. It's fine...
Our edge is ogee straight.


 o
RE: Thickness of 2cm Countertop Underlayment (5)

Hi Suzieca - thanks for that. All this anecdotal evidence is very useful.

All, I've gone with 19/32 now... it was all they had a Home Depot. Thanks for all the advice -- much appreciated!


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!


Return to the Kitchens Forum

Instructions

  • You must be a registered member and logged in to post messages on our forums.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review the contents and make changes.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • It is illegal to post copyrighted material without the owner's consent.
  • HTML codes are allowed in the message field only.
  • No advertising is allowed in any of the forums.
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.



 
Click here to learn more about in-text links on this page.