Post Form Counter Top gaps

[NCKIII]

I install cabinets ofr a local builder and install post form tops. I scribe them to the wall after using 1 x 4 under layment to build up the height for top drawer clearance. I've gone back to a couple houses and noticed up to 1/4 gaps mainly on the back walls. These are interior walls of the house. These tops are on bathroom vanity cabs.
Can particle board shrink that much? Are the walls moving? Is it just a matter of not letting the tops acclimate long enough in the house?

[joseph]

bummer . my thoughts would be stud shrinkage .though i have mdf expand it is pretty clear to the eye that it has .can you do some moisture checks .check the ones with a gap and the ones that haven't gapped .see if there is a difference . if it was the to wouldn't the gap be uniform throughout he whole top?

[m beezo]

are you sure the orignal countertops were scribed to the wall? I have seen lots of tops that were not scribed and there are gaps just filled with caulk. Anyone that works with a long straight piece of lumber against a piece of drywall will be amazed at the amount of bumps and valleys that you did not know were there.

[Ottoman]

Although I cannot tell you exactly why that happens, I can tell you how to fix and prevent it. Use metal "L" brackets and use two screws to anchor them us into the top. Set them back from the cabinet nailer about a half inch. Place them at the location of the studs. Drill a clearance hole, 3/16" should suffice, in the nailer and using a 3" screw draw the counter top to the studs. Don't over do it and crack the backsplash. Every other stud is more than enough. It helps to prep before you set the tops on. You will never have another call back again for this.

I suspect it's a combination of cabinets shifting and walls moving. I would be suprised if it was the tops themselves.

[Hickorywind1]

Where the cabinets securely fastened?