What Size Plywood Under Quartz Countertop

Installing a quartz countertop can greatly enhance the look and functionality of your kitchen or bathroom. Quartz is an engineered stone that is very durable, stain-resistant, and easy to maintain. However, proper installation is key to ensuring your countertop lasts for many years. An important part of the installation process is selecting and installing the right plywood substructure underneath the quartz.

What is the Recommended Thickness for Plywood Under Quartz?

The recommended plywood thickness for underneath quartz countertops is 3/4″. This thickness provides a stable, sturdy base that can handle the weight of the quartz slabs.

Anything less than 3/4″ may not provide adequate support, while thicker plywood like 1″ is unnecessary and will only drive up costs. 3/4″ plywood is readily available at home improvement stores and lumberyards and strikes the right balance between strength and affordability.

Why Do You Need Plywood Underneath Quartz?

There are a few key reasons why plywood is used under quartz countertops:

  • Support: Quartz is very heavy, weighing approximately 15 lbs per square foot for a 3cm slab. The plywood provides critical structural support to bear the weight without sagging or cracking.
  • Stability: Plywood creates a stable, flat surface for mounting the quartz. This prevents shifting, rocking, or other movement that could cause the quartz to crack.
  • Protection: A plywood substrate protects the quartz from inconsistencies or imperfections in the cabinet base underneath.
  • Adhesion: Plywood gives the adhesive or thinset a solid, reliable surface to bond to. This creates a long-lasting connection.
  • Moisture protection: Plywood forms a moisture barrier between the quartz and the cabinetry, protecting both from water damage.

In summary, plywood provides the essential combination of strength, stability, protection, and adhesion. Quartz manufacturers and industry standards universally recommend using plywood under quartz countertops.

What Type of Plywood Should Be Used?

While 3/4″ is the recommended thickness, you also need an exterior-grade, void-free plywood for under quartz countertops. The two best options are:

  • Marine-grade plywood: This is made with water-resistant adhesive and designed to withstand moisture over long periods. It is very stiff and durable.
  • Underlayment-grade plywood: This type is made specifically for flooring and countertop substrates. It uses premium wood veneers without voids or knots.

Both are excellent options that provide a smooth, consistent substructure for natural stone countertops. Avoid using CDX, OSB, lauan or other low-cost plywood grades that are prone to swelling and deterioration when exposed to minor moisture. Spending a few extra dollars on marine or underlayment plywood will pay off in the long run.

How to Install and Prepare Plywood for Quartz

Proper installation of the plywood is just as important as using the right type. Here are some best practices:

  • Cut plywood to precisely fit the cabinet base using a circular saw. Seal all cut edges with primer/paint.
  • Fasten plywood to cabinet bases using screws, 6” apart around the perimeter and 8” apart across the field.
  • Make sure plywood is flat across the entire cabinet base – shim if needed. Screws should be flush.
  • Fill any seams or screw holes with epoxy filler; sand the plywood surface smooth.
  • Test fit the quartz slab and make any adjustments to ensure it lays flat and makes full contact with the plywood.

Preparing the plywood surface correctly will allow for superior adhesion and prevent cracking or chipping on the edges of the quartz. Take the time to properly install the plywood substructure before adding the quartz.

What are Other Options Besides Plywood?

While plywood is preferred, there are a few alternative options:

  • MDF (medium density fiberboard): MDF is more affordable and widely available than plywood. It can be used on short runs of cabinetry. However, it doesn’t stand up to moisture and humidity over time.
  • Reinforced concrete: Concrete offers benefits like fireproofing and sound dampening. However, it requires building specialized cabinet bases and is cost prohibitive for most homes.
  • Steven’s Elevated Platform: This engineered wood substrate made specifically for quartz countertops consists of a top layer of plyboard with an engineered frame. It adds cost but creates a super stable surface.
  • HardieBacker cement board: This is sometimes used as a moisture-resistant substitute for plywood, but does not provide the same structural strength.

In most cases, the best option remains 3/4” void-free plywood. It has proven strength and durability to support quartz for many years. Only use alternatives if plywood is unavailable or your project has specific structural needs that demand a reinforced concrete or elevated platform substructure.

FAQs About Plywood Under Quartz Countertops

Should I use anything between the plywood and quartz?

No additional layers are necessary between quartz and plywood. Attaching the quartz directly to the plywood allows for optimal adhesion. A thin skim coat of mortar is all that is needed on top of plywood before setting quartz.

What about gaps or height differences between plywood sheets?

Any height differences greater than 1/16” between plywood sheets should be sanded/planed flush for a seamless quartz installation. Use shims to fill any gaps prior to attaching the quartz.

Should I use green board or purple board instead of plywood?

Moisture resistant drywall like green/purple board is not strong enough to support natural stone. It will eventually crumble under the weight. Only use void-free plywood or the other substructure systems mentioned above.

How is plywood attached to the cabinet bases?

Use coarse-threaded wood screws, 6” apart around the edges and 8” apart in the field. Screws should be countersunk flush with the plywood surface to prevent obstructing quartz placement.

Can I use laminate countertop as the substrate under quartz instead of plywood?

No, laminate countertop substrates do not have the structural strength to support heavy quartz slabs long-term. You should always remove old laminate tops and install new 3/4” plywood when switching to quartz countertops.

What about using a Murphy bed wall as the base under a quartz desktop?

Murphy bed walls are normally not rated to bear heavy stone loads permanently. Add a properly supported 3/4” plywood subtop to safely bridge between the wall and quartz countertop.

Key Takeaways

  • Use 3/4” thick, void-free plywood under all quartz countertops
  • Marine and underlayment grades offer moisture resistance and strength
  • Cut plywood to fit cabinets exactly; prep surface for maximum adhesion
  • Plywood provides essential structural support, stability, and protection
  • Alternatives like MDF or concrete may work but have limitations
  • Proper plywood installation prevents future problems with quartz cracking or chipping

With the right plywood thickness and quality, you can install beautiful, durable quartz countertops that will last for many years in your home. Taking the time to properly prepare the plywood substructure is a key first step. Follow the recommendations outlined above, and you can feel confident your new quartz countertops will maintain their smooth, flawless appearance long into the future.

How to Select the Right Thickness for Your Quartz Countertops

Quartz countertops are available in thicknesses ranging from 2cm up to 5cm. The thickness you choose will impact cost, aesthetics, durability, and ease of installation. Here are some factors to consider when selecting quartz thickness:

Standard Thicknesses for Quartz Counters

  • 2cm (3/4”): The minimum thickness for quartz countertops. Provides more affordability. Best for low-use settings.
  • 3cm (1 1/4”): The most popular and recommended standard thickness. Balances cost and durability. Suitable for most applications.
  • 4cm (1 1/2”): Provides enhanced strength for heavy usage areas. Minimal added cost over 3cm.
  • 5cm (2”): Maximum thickness typically used. Provides the greatest durability and fire resistance. Significantly higher cost.

Factors to Consider

Usage Level

Thicker quartz performs better in high-traffic kitchens or commercial settings. Home cooks may prefer 3-4cm for added durability. Low-use bathroom vanities can utilize 2cm.

Overhang Lengths

Long overhangs beyond the cabinet base increase stress on the slab. 4-5cm thickness helps reinforce longer spans of overhanging quartz.


Thicker quartz offers a substantial, stone-like look. 2cm has a more delicate aesthetic for minimalist contemporary designs.


Thicker quartz tops add more weight requiring stronger cabinet bases. This is amplified in larger kitchens.


Due to higher materials cost and labor, thicker quartz comes at a steeper price. Decide if added durability justifies increased expenditure.

Edge Profile

Thicker edges allow for more intricate profiles like triple waterfall edges. Thinner 2cm slabs limit you to basic eased or pencil edge profiles.


If you plan to incorporate a matching quartz backsplash, a thinner 2cm profile can help reduce material usage and cost.

Installation Method

Seamless appearing quartz fabrication requires thinner 2cm slabs. Thicker quartz needs visible seams between slabs.

Recommendations by Application

Kitchen Countertops

Most experts recommend 3cm quartz for kitchens. It handles daily use well and keeps costs lower. Select 4cm for heavy prep/cooking usage or 1 1/2” overhangs.

Bathroom Vanities

2cm quartz works well for bathrooms that see lighter usage. Undermount square sinks are fine. Avoid asymmetric vessel sinks with 2cm.

Laundry & Utility Rooms

These high-moisture environments warrant thicker quartz in the 3-4cm range for increased water resistance and durability.

Bar Tops

Quartz bar tops should be at minimum 3cm thickness to support glasses/bottles and withstand harsh chemical cleaners. Go 4cm for added assurance.

Restaurant Countertops

Commercial settings need maximum durability, so 5cm quartz is ideal. This thickness stands up to heavy commercial use.

Desks & Tabletops

For desks and tabletops, 2cm quartz provides elegant appearance at lower materials cost. Limit overhang distance.

Key Takeaways

  • Standard thicknesses for quartz range from 2cm up to 5cm
  • 3cm is the most commonly used and recommended
  • Consider usage level, overhangs, aesthetics, and budget
  • Kitchens often benefit from 3cm, while 2cm works for bath vanities
  • Commercial settings should use thick 5cm for durability
  • Proper support and installation is critical regardless of thickness

Selecting the right thickness involves balancing durability, cost, and the look you want. Many residential settings are well served by the universal 3cm thickness. Size up or down based on your specific needs and budget. With smart planning, you can customize the ideal quartz countertop thickness for your home.

How to Measure and Prepare for Installation

Careful measurement and planning are crucial steps before installing quartz countertops. Here is a complete guide on how to measure correctly and prepare for flawless quartz installation:

Measure Twice, Cut Once

The old carpenter’s motto applies especially to quartz fabrication. Accurately measuring your existing countertops and cabinet run is vital for proper quartz cutting and fitting.

Use a steel measuring tape for precision. For corners and walls, make sure the tape follows straight edges. Record all inside and outside dimensions.

Double check all measurements, and have a second person verify to catch any errors. Also account for uneven walls and imperfect 90-degree corners.

Allow Space for Overhangs

Standard quartz overhang on front edges is 1 1/4”. Make sure to factor this into measurements. Allow more overhang space for thicker quartz or waterfalls.

Also account for extra overhang with apron fronts or other overlapping edges where quartz may run longer. Getting overhang length right ensures proper fit.

Mark Plumbing Fixtures Precisely

Use painters tape to mark the exact location of sink cutouts, cooktops, and any other required openings.

Measure hole diameters carefully, and note distances from corners/edges with precision. Any mistakes at this stage can ruin the quartz fabrication.

Check for Level & Plumb

Use a quality level tool to confirm countertop bases and walls are perfectly level. Look for any out-of-plumb corners or uneven cabinets.

marks all inconsistencies. They must be remedied prior to installation day, or you may end up with gaps, unstable surfaces, or misfit slabs.

Prepare the Space

Clear countertop space entirely. Remove existing tops, walls obstructions, and backsplashes if present. Also evacuate drawers from cabinets.

This allows clean access for the installation team. Having an empty, prepared workspace helps the process go smoothly and safely.

Material Staging Area

Discuss ideal staging areas for quartz slabs and tools with the installers. This keeps the work zones accessible without cluttering other home areas.

Proper planning of logistics, measurements, overhangs, and space readiness makes for efficient quartz fabrication and trouble-free installation day.


How are seams handled on longer runs?

Quartz cannot be fabricated in endless lengths. Longer runs will require seamed connections between slabs. Experienced installers will make seams inconspicuous.

What if my walls or cabinets are uneven?

Shims can be used to compensate for out of plumb walls or unlevel cabinets. This evens out the base for proper quartz placement.

Is special adhesive or mortar used to install quartz?

Most fabricators use high-quality polyester resin adhesives to bond quartz to substrate. It creates a permanent, waterproof connection.

Should I be present for the entire installation?

Your quartz provider should review the whole process including needed access, timelines, and home readiness. Then you simply need to be present at key times to approve.

How long does the installation process take?

That depends on total countertop square footage. But expect installers to need 4-6 hours for an average 10′ kitchen quartz install. Large or intricate jobs can run 8-10 hours.

Key Takeaways

  • Measure thoroughly and double check all dimensions
  • Factor in appropriate overhang space
  • Clearly mark fixture and opening locations
  • Ensure level cabinet bases and plumb walls
  • Clear all obstructions and prepare workspace
  • Discuss staging areas and installation plan with team
  • Advance planning makes for smooth quartz install process

With careful measurement, space readiness, and communication, your installers will be setup for quartz fabrication success.

How to Care for and Maintain Quartz Countertops

Quartz is highly durable, but proper care is still needed to keep your countertops looking pristine. Follow this guide on caring and cleaning quartz:

Daily Maintenance

  • Wipe up spills immediately to prevent stains, especially from red wine, coffee and oil.
  • Use mild soap and water for quick cleanups. Avoid abrasive cleaners.
  • Rinse thoroughly after cleaning to remove any lingering residue.
  • Blot dry any excess water to reduce water marks.

Regular Cleaning

  • Clean quartz 1-2 times per week routinely.
  • Use a non-abrasive quartz cleaner or mild vinegar/water mix.
  • Apply cleaner sparingly with a soft cloth, rinse completely.
  • Too much cleaner can leave a film that accumulates over time.

Stubborn Stains

  • For stubborn stains/residue, let a damp cloth soaked in a ammonia-free glass cleaner sit on the spot for 5 minutes then scrub gently.
  • You can also try mixing baking soda and water into a paste, letting sit for 5 minutes and scrubbing.
  • For dried spills, a plastic putty knife can help scrape off the deposit if needed.

Etching and Scratches

  • Avoid using any highly acidic products like lemon/orange juice that can etch quartz. Wipe up immediately if they spill.
  • Do not cut or chop directly on quartz; always use a cutting board. This can scratch, chip or crack quartz.
  • Minor scratches can often be buffed out using fine grit sandpaper and a small circular polishing tool.


  • Periodically resealing quartz every 2-3 years will improve stain resistance. Use a dedicated quartz resealing product, not grout sealant.
  • Annual reconditioning by a professional refreshes the surface shine.

Other Care Tips

  • Avoid exposing quartz to excessive heat. Always use trivets under pots, pans or baking sheets.
  • Check quartz edges near walls annually for any sealant gaps that need re-caulking.
  • Thoroughly dry any water that spills near the seam of a quartz backsplash to prevent moisture penetration.

With proper care, your quartz countertops will stay looking like new for decades. Consistent maintenance also helps uphold warranties. Contact a quartz pro for deep cleaning or repairs.


Can I use bleach or hydrogen peroxide to disinfect quartz?

No, avoid harsh cleaners like bleach that can strip color pigments or burn the surface. Use a dilute vinegar solution or 70% rubbing alcohol