Question by Guest_988593721: Will large particle-board kitchen cabinet support granite countertop?
I am having to replace a kitchen cabinet because of a serious water leak that water-logged the particle boards. My old countertop has been tile, and it has to go, as well as the cabinet. I am told that granite would be the best replacement, in terms of eventual resale value. I have read on the Internet that granite countertops should not be used on cabinets that are mostly particle board. Both contractors and sales people at the home improvement stores consistently say that it would be all right to use and recommend it strongly. Which is correct? The cabinet has solid wood doors but the rest, so far as I know, is particle board. I don't want the cabinet to collapse, but I do like the look of granite, especially since the price has come down.
Answered by LCD: There are a couple of contractors on here that I think have a lot more cabinet experience than me, so listen to them if they chime in - Todd Shell or Don for example.
However, a normal particle board cabinet (assuming probably 3/4" particle board, not super-thin ultra-cheapo chinese box store stuff) can easily take a 200+ pound worker sitting or kneeling on it - so maybe 50-100 PSF applied load on the cabinet. Granite is typically not over 2" thick for countertops and commonly 1 to 1-1/2" thick, which is 20-30 psf - FAR less than a person on the countertop, so as far as strength I would not be worried about that.
Where the worry does come in is if the particle board gets wet, as it loses most of its strength and creeps and oozes out from under the load, so a hidden leak could cause a sagging cabinet unable to carry the weight, which could then cause the countertop to break. My solution, taught to me by my tile and countertop Dad about 50 years ago, for use with all tile, stone or thin synthetic countertops, is to put down a 3/4" exterior plywood underlayment to distribute the load, support the countertop where it is narrow around the sink cutout, and provide a good flat surface to lay the countertop on. Adds about $150-200 total to job cost with the wood and construction adhesive and labor, but removes a LOT of risk with the countertop, especially during installation. I have found countertop installers like it as a base to install on, and it supports the countertop way more uniformly than wood shims on top of the cabinet edges. Does require either a 3/4" or more front drop lip or edging on the countertop, or a handwood trim strip across the top of the cabinet to cover the exposed edge - none of which are tough to do, and a supporting strip under the front overhanging edge is a good idea to support it anyway. Butt joints should have bonded wood support under the edges (1x3 or 1x4 construction glued to the underside of the joint) so there is no tendency of the joint to separate vertically or bend down under load.
Be sure to check warranty up front, in case countertop manufacturer or installer voidswarranty if put on particle board cabinets, though I have never seen that.
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