Need help installing bowed laminate counter top

[Benjimin Young]

A slightly bowed counter top.
I just picked two custom but standard profile laminate counter top with back splash. The 6ft one is fine but the 10 ft is bowed, meaning from front to back, over 22" it sags down about 3/32 in the middle and this occurs across the entire 10 foot length, e.g. same sag at both ends, see sketch. I understand this can happen due to the laminate on one side and open particle board on the back side but my concern is the sink will not set flat when installed. So, I was thinking of doing the following:
1) place the counter it face down on the floor in my house with boards along the back and front edges, then apply weight along the center and at the same time place my de-humidifier on top.
2) when installing the counter, if it is still bowed, adding shims near the center of the sink however I am not sure how much pull down load a screw in 5/8" particle board can actually apply before popping out.
The supplier is supportive and suggests I install it but will back me up if it does not flatten. I'd rather not have to ship it back and wait for another counter.
If any members have tips on how you would prep and or install the counter so the sink sits flat, please share them.

[Richard Coers]

My assumption is that the long section saw a major humidity change or actually was loaded during some rain. That swelled the back surface and hence the bow. I'd put in the shim and set them on the cabinets. Open all the cabinet doors and put some floor fans in the room, pointed at the cabinets. It should come into shape fairly quickly and you can then do the final install.

[andy bessette]

Replace it with a quality unit.

[Ron Selzer]

Replace it with a quality unit.
x2
Ron

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[Benjimin Young]

Hi Richard and thanks for your time and response. A good idea, I will check moisture content although I think the unit is dry at least to my normal house humidity as it currently is laying upside down on my dinning room floor. A test with a 200 lb person standing on the counter did temp correct the cupping so I need about 200 lbs per sq ft force to correct the cupping ( a lot of force for screws in 5/8" chipboard). But after sleeping on the problem I thought once the sink is cut out it should weaken that area and require much less "screw' force to pull the counter around the sink into flatness, at least that is my hope. I like your idea of placing a thin shim in the center which may help. If all else fails I am out some time and labor but with some learning to share. The bad news is I will have to wait for the newly imposed C19 lockdown for Ontario Canada to end before I can truck the counter back to the fabricator who will replace it. I will repost the results after trying. Thanks again.

[Tom Bender]

That much sag will also cause a puddle which will reflect badly on your work. Drying it out should fix it. Put it upside down on the floor and put a fan on it. If it doesn't flatten in a couple of days replace it.