# "cupping" in prefab counter tops



## Nestor_Kelebay

I've noticed that the prefab counter tops sold by Home Depot (and others) here in Winnipeg have curvature to them which I don't notice in installed plastic laminate counter tops.

Specifically, the curvature that I'm referring to is the front-to-back curvature so that if you were to lay a straight edge from the front bullnose to the rear backsplash of the counter top, you'd see a gap between the straight edge and the counter top.

I've been told that this curvature is called "cupping".

I've also been told it's caused by:

1. the plastic laminate shrinking as it cools, and
2. the particle board swelling as it absorbs moisture from the air.

Does anyone know of a web site or other source that would establish with certainty what this curvature is called and what causes it?


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## handyguys

if its what I'm thinking of its part of the design. Its done that way so that you contain a spill (somewhat) to the counter. Its part of the design and not a defect (if its what i'm thinking about)

The technique is called postform - essentially the laminate follows from the front edge, around the bull nose, and up the backsplash.


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## Nestor_Kelebay

No.  I fully understand that the concept behind the design in the picture is to contain a liquid spill.

I'm talking about the UNINTENTIONAL curvature of the counter top from front to back.  That curvature forms in the counter top after it's manufactured, and is not part of the design of the counter top.  If you put a straight edge, like a spirit level, on the counter top and perpendicular to the back splash, you'll find a gap from 1/16 inch to over 1/8 inch between the top and the spirit level.

The difficulty this creates in installing counter tops is that if you have an "L" shaped counter top, then the "cupping" of both tops has to be identical to get them to meet properly in the mitered corner.  If one top is flat, and the other cupped, then you simply can't get the tops to meet well in the corner.  I've come across this so many times, that now I spend an hour at the home center every time I buy a pair of counter tops trying to find the flattest ones.

Maybe go look at a prefab counter top at Home Depot or Lowes, and you'll see what I mean.

Thanks anyhow for trying to help.


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## inspectorD

It comes down to..they are junk. The board material is junk, and the laminate they cover it with is very thin...and junk.
The combination of the way it is heated to get the formica on, then cooled and the moisture in the building does it, and it will not go back to original.
Those companies play the #s game, they sell it and most times it will not come back...yet folks still go there.

Can you tell I'm biased? But that comes from professional experience...if they did a good job , contractors would only shop there. 
The #s on diy are much greater , with less of an expectation level.

Just :2cents: worth.

Make your own top...or contact a post form company.


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## finishguy

Cupping in laminate countertops is almost always caused by laminating only the top surface of the particle board. A good quality c-top should always be sealed on the bottom side with another type of laminate called backer, which is a very thin layer of resin impregnated paper. In woodworking they say whatever you do to the face should be also done on the back in order to seal out moisture, which is what will cause cupping. Usually only pro c-top manufacturers, or custom cabinet shops will do this. If you are thinking of installing a cheaper "cupped" c-top, you should be okay as long as it is properly glued down. Most installers will use Liquid Nails or any other kind of construction adhesehive.


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## Nestor_Kelebay

Thank you so very much for your personal opinion, InspectorD.

But what I need is not so much an opinion, but a reliable source of information to tell me what this kind of warping is called and a knowledgeable explanation for what causes it?

You see, a former tenant scorched on of my plastic laminate counter tops, and I really don't want to go before a hearing of the Residential Tenancies Commission and say "My laminate counter tops are junk.  The particle board core is junk and the laminate glued to it is garbage.  But, I still want to put a real big dent in my former tenant's damage deposit for scorching that worthless crap."

Thanks for your opinion, but I remain...
looking for a source of information that can tell me what this kind of warpage is called and what causes it.


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## finishguy

That warping is caused by only laminating the face or top surface of the particleboard. A quality c-top will have both sides laminated in order to seal the bottom from moisture. The bottom is almost always laminated with a very thin resin coated paper known as backer.


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## Nestor_Kelebay

Finishguy:

I suspect the warping is the result of what you say.  Since the laminate will prevent moisture from being absorbed into one side, but not the other, then the top will bend concave upward as it absorbs moisture.  And, of course, the longer it's exposed to the atmosphere and the more it absorbs, the greater the warping.

But, I'm going to be arguing my case in front of 3 people who consider that I don't know anything since I'm not an "expert" on the subject.  What I really need is to find a web site or some other authoritative source of information that will confirm what you (and InspectorD said).  I'm having no end of trouble finding anything about warped particle board plastic laminate counter tops on the internet.


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## inspectorD

nestor, I know I get he77 for this sometimes,..but did you contact the company and ask them?
Cupping is a fact of wood...and any wood product. The moisture moves inside the cellulose material ...always. I have worked in many cabinet shops, and when we delivered tops from the shop to the site...they moved by the time they got installed if they where not sealed.
I do not know of a source to look at. 
These guys do it right...call them.http://www.vtindustries.com/images/news/3.pdf

I'm sure they will tear up the competition, and help answer your question.


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## oldognewtrick

Nestor_Kelebay said:


> You see, a former tenant scorched on of my plastic laminate counter tops, and I really don't want to go before a hearing of the Residential Tenancies Commission and say "My laminate counter tops are junk.  The particle board core is junk and the laminate glued to it is garbage.  But, I still want to put a real big dent in my former tenant's damage deposit for scorching that worthless crap."
> 
> QUOTE]
> 
> Nestor, what is the tenats arguement for his damaging your counter top? If he broke it why won't he fix it?


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## Nestor_Kelebay

Inspector:
I'll phone Belanger tomorrow.  They are the manufacturers of the prefab tops sold by both Home Depot and Rona here in Winnipeg, and see if someone there will acknowledge that the tops are cupped.  I think it'll be an accomplishment to even get them to do that.

Oldog/Newtrick:
The guy says that a pot boiled over on the stove, so he took it off the stove and put it on the counter top.

Every one of the counter top places I e-mailed pictures of the damage to (to get cost estimates to replace the top) said that it couldn't be fixed in any reasonable way.  The best you can do is install a cutting board where the scorch is, and that's not feasible here because it's only 6 inches away from the sink, so it's in a wet area.

I have no doubt that the cupping is due to absorbtion of moisture on one side of the laminated slab.  And, I've come across that over the past few nights searching the internet for information about this.  Plenty of the Q&A forums on the internet have references to the warping of prefab counter tops, but I can't find a particle board manufacturer's web site or counter top manufacturer's web site that deals with this problem so that I can say:  "These people manufacture particle board or plastic laminate counter tops and so they are experts on the subject, and they say particle board will warp if sealed on only one side, cuz then only the other side will expand due to moisture absorbtion from the atmosphere."

And, the reason why I need that is because it's an "L" shaped counter top, and of the two Belanger prefab counter tops I purchased to install in that suite, one had a slightly amount of cupping to it.  So, if one counter top is flat and one curved, you simply can't get them to meet flush all along the mitered joint where they meet.

So, being a reasonable landlord, I put a note on the incoming condition report saying that the two tops didn't meet perfectly in the corner, and the front bullnose of one top is about 1/16 of an inch above the other.

And, now the tenant is saying the counter tops were already damaged.  There's proof on the incoming condition report.  It says they didn't meet perfectly at the corner.  So they couldn't have been installed properly or correctly, and so the tops were in need of repair already, and so it's not like he scorched a good counter top, he scorched a top that was already defective.

So, I somehow have to explain to "lay" people (political cronies, really) that the counter tops didn't meet perfectly in the corner because one had a bit of cupping to it, and that this cupping is not "damage" caused by a previous tenant (or the original installer, yours truly), or due to improper installation, but occurred naturally after the top was manufactured, and that given the tops that I purchased, I couldn't have avoided that problem.

As it stands now, I can prove to them that wood swells when it absorbs moisture (and that's easy to do), and I can lay out the logic above that would result in the conclusion that there should be warpage.  The problem is that these people aren't builders or even wood workers.  If any of them are insecure in their knowledge about wood, they may think I'm just trying to hoodwink them, and would remain unconvinced.  That's why it would be best to have an authoritative source of information that just spits it out so it's there in black and white and there's no concern that I'm trying to hoodwink anybody.

The tenant isn't stupid.  He's not denying he scorched the counter top because there's no hope of that argument succeeding.  He's claiming the counter tops were defective or their installation was defective (as evidenced by the incoming condition report), and so he scorched a nearly worthless counter top.  That's why my getting up there with InspectorD's information and telling them how laminated counter tops are garbage wouldn't have helped my case.


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## inspectorD

Good luck Nestor in finding that info. My feeling is no one has done this research, to costly for a replaceable peice of junk.
May I offer a solution, glue a piece of granite or tile over the damaged top so the person has a place to put hot pots.


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## Nestor_Kelebay

So I phoned Belanger Laminates in Quebec at 1-800-361-5976 and talled to "Gilles".

He says he just calls the front-to-back curvature "warping".  He says he isn't sure what causes it, but the fact that one side of the particle board is sealed whereas the other side is exposed to the humidity in the air is the explanation that speaks loudest to him.

He says that this "warping" is something that I'm the only one in the world to have brought to Belanger's attention, and for some reason no one else is concerned about it, and so the company has no plans to do anything to seal the bottoms of their counter tops in an attempt to prevent that warping from occuring.  He says that it's just a matter of buying two counter tops with the same degree of warping to get nice corners.

At least I have a name and phone number of an "expert" now.  The only consolation I have is that the scorched counter top is the one that lays flatter.  The non-scorched counter top is the one with the more warping in it.


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