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Unread 04-16-2021, 06:49 PM   #8
Registered User
Join Date: Jan 2015
Location: Coeur d'Alene, Idaho
Posts: 89
@KG (Bubba)

That "gravel" CBU damage was caused by me. Post rant, after I slept on this, I decided to just treat this like a drywall repair. Cut out an 8" x 6" rectangle, and replace, probably by overlapping the adjoining cell which has yet to be cut. Add a plywood backing plate to knit the drywall and/or CBU together. It's not as big a deal as I made it out to be.

I was mostly ticked at the time because I was trying to wedge the Durock into the "slot" where the damaged drywall sat between the granite countertop and studs, and it didn't compress to fit (concrete board doesn't compress, who knew?). While I was jockeying to cut down the board to fit, I damaged the opposite corner. I used Durock to build a fireplace surround last year, and I agree, it is easy to stick stone to it (with the help of a sticky mortar like Ardex x77).


The electrical boxes will all need to sit proud to come even with the eventual Quartz ledger/stack stone, so I'm adding box extenders. The plates will sit close to even with the stone (which I may have to grind a bit to fit). That look worked out OK for the fireplace, and a prior backsplash project (see pix).

To all: As far as blocking in general, my goal is to ensure there is no more than 8" of space between two screws. So, where a vertical pipe (Or other item) prevents putting a horizontal blocking stud at the bottom of the backsplash, I'm adding several 6", 2x3 vertical blocks attached to structural studs, stacked, to close the 14.5" gap between studs to something closer to 10". It won't be near as strong as a proper block, but it'll help prevent flexing of the bottom of the backsplash, between the two studs.

For areas where I can reach the drywall (sides, under cabinets), I'm just handling blocking like I would a dry wall patch, i.e. putting 4"x6" or 10" x 6" plywood plate behind the joint. Secure with drywall screws to the drywall, and CBU screws to the CBU, to lock in the patch. The result is pretty strong.

So, adding the structural studs, the blocking, backing plywood plates, the 1/2" Durock, a whole bunch of CBU screws (plus a few drywall screws), 1/2" of combed mortar, and the back buttered 1"quartz panels, there's a lot of stability in that backsplash wall.

I'll post some progress pictures, uhhh, once I make some progress. ????

Thanks for your answers, and interest.

(Note: For some reason, there's no "reply" button after each post, so quoting and replying to person's post via HTML is problematic. That's why I referred to each person by "@".)
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