How to Provide Support for Dishwasher Under Quartz Countertop

Installing a dishwasher under a quartz countertop requires some special considerations to ensure proper support and prevent cracking or damage. Here is a detailed guide on how to provide adequate support for a dishwasher under quartz.

Selecting the Right Dishwasher

When choosing a dishwasher for under a quartz countertop, opt for a slim, compact model. Look for dishwashers with an ADA (Americans with Disabilities Act) compliant height of 32-34 inches. Standard dishwashers are usually taller and could put pressure on the countertop.

Compact models like Bosch 300 series or Whirlpool WDP350PAW are ideal choices. Also ensure the dishwasher has an adjustable/removable top panel to customize the height as needed.

Providing a Solid Base

Quartz countertops need a perfectly level, rigid base for seamless dishwasher installation.

  • Use 3/4 inch exterior grade plywood to build up the cabinet base. This creates a sturdy, smooth surface for the dishwasher to sit on.
  • Alternately, install a solid surface countertop substrate like Cosentino, Caesarstone or Pentalquartz recommends. These are engineered supports specifically for undermount sinks and dishwashers.
  • Secure the base tightly to the cabinet frame using screws. Check for levelness using a spirit level.

Front Support

With no front lip support, the weight of the dishwasher can cause the quartz to bend or crack over time. Provide adequate structural support at the front:

  • Attach 2×4 wood blocks securely to the cabinet sides using screws. Install them flush with the front edge of the cabinet base.
  • Use quartz strips or metal L-brackets designed for dishwasher support. Screw them under the countertop overhang.
  • Build a front frame support using 2x4s attached horizontally between the side cabinet walls. Sit the dishwasher atop this frame.

Securing the Dishwasher

Use brackets, screws and adhesive to keep the dishwasher firmly in place:

  • Attach L-brackets to the underside of countertop side walls using small screws. Fasten the dishwasher to these brackets.
  • Use silicone adhesive caulk to glue the top of the dishwasher to the quartz underside. Allow to cure completely.
  • Drive long screws through the inside of the dishwasher tub into the cabinet base. This prevents the unit from tilting forward.

Gap Filling

Seal any gaps between the dishwasher and countertop using:

  • Silicone caulk, tooling it into crevices using a caulking tool. Wipe away excess.
  • Custom trim pieces or molding cut to size. Adhere using silicone adhesive.
  • Heat resistant cork tape pushed into openings.

This prevents moisture damage and debris accumulation in gaps.

Door Alignment

Misalignment with cabinetry affects function and aesthetics.

  • Ensure the dishwasher door is centered under the countertop before finalizing installation.
  • Use shims as needed between the dishwasher and cabinet to adjust the position.
  • Confirm the door opens and closes smoothly without rubbing against adjacent surfaces.

With proper base support, secure fastening, and gap sealing, a dishwasher can be installed under quartz countertops without any stress or damage. Take careful measurements and allow for height adjustments during installation.

Frequently Asked Questions

What thickness plywood should be used for the base?

3/4 inch exterior grade plywood is best for a smooth, sturdy base under quartz countertops. Anything thinner has a risk of bending or warping over time.

What height is recommended for dishwashers under quartz?

Look for compact models with an ADA compliant height of 32-34 inches for a good fit under standard quartz countertop thickness.

How can I align the dishwasher door with the cabinets?

Use shims between the dishwasher frame and cabinet sides to adjust the position if needed. Remove shims once the door is centered and opens/closes smoothly.

Should I glue the dishwasher to the quartz?

Yes, apply a silicone adhesive caulk between the top of the dishwasher and quartz underside. This creates a bonding seal.

What can I use to fill gaps around the dishwasher?

Silicone caulk, custom trim pieces, cork tape are good sealants. Fill gaps to prevent moisture damage and food/debris accumulation.


Installing a dishwasher under quartz requires strategic planning and preparation. Provide a solid base, ample front support, secure fastening, proper gap filling, and alignment with cabinetry. Compact dishwashers work best for under quartz counter applications. With careful installation, you can have an integrated dishwasher without worrying about countertop stress or cracking. Follow the recommendations outlined here for a seamless and functional installation.