Before installing granite countertops, a lot of people put down a layer of plywood, but can you install granite countertops without plywood?
When installing granite countertops, you will not need an underlayment of plywood if the granite has a thickness of 3 centimeters (about 1 1/4 inches). However, for granite with a thickness of 2 centimeters (about 3/4 inches), you will definitely need to use plywood for support.
Just like any heavy stone, granite can crack if not protected properly. 3 centimeter granite is much sturdier than 2 centimeter granite and will not break or get damaged when installed without plywood. However, 2 centimeter granite needs support under it since it is less sturdy, so having a plywood underlayment is a must.
Why Use Plywood for 2cm Granite Instead of a Different Material?
Plywood is an engineered wood that comes in various grades ranging from A through D. Grade A is the best quality and most expensive while Grade D is the worst quality and least expensive. Almost everyone installing 2cm granite countertops should use Grade A plywood.
With so many different materials available, why is plywood considered the gold standard for supporting 2cm granite countertops?
Think about it: plywood is inexpensive, easy to find, and durable. Since other materials tend to be pricier and less durable, using plywood is a no-brainer.
Also, plywood does a great job of balancing out the granite and keeping it level and flush with your backsplash and cabinets. A plywood underlayment also provides better support for your granite countertops than most other materials.
Similarly, applying pressure to the countertop or putting heavy things on top of it will not cause the granite to give way. The plywood also allows for the weight of the granite to be evenly spread throughout instead of it being concentrated in one particular place. This greatly helps prevent cracks and breakage, especially in weaker areas like above the dishwasher.
Why Some People Mistakenly Think You Always Need Plywood
Unfortunately, there is a lot of misinformation floating around the Internet about installing granite countertops. You need to be careful.
Conventional wisdom wrongly tells you that because granite is a heavy material it will not be able to hold its weight without having plywood underneath it. Also, some say no matter what the thickness of your granite is you should always have plywood underneath in order to err on the side of caution. However, both of these claims simply are untrue when it comes to 3cm granite.
The cabinets that your 3cm granite slabs will rest on serve as plenty of support, and unnecessarily complicating a countertop installation will waste your time and money. Remember, if you use several smaller slabs (instead of one or two big pieces) and are careful to have your fabricator use mesh under the countertop where your dishwasher goes, you should have no problem with your countertop installation.
That said, for 2cm granite you will definitely want to have plywood underneath. It will absorb any of the pressure put on the granite, prevent cracking, and help the countertops last longer.
Does 1cm Really Make That Big of a Difference?
In short, yes. Believe it or not, one centimeter is the difference between needing plywood underlayment and not needing it at all.
The weakness in granite and any natural stone comes from its veins and dry seams. Both 2cm and 3cm have these characteristics. However, a 2cm slab of granite is more prone to weakness as a result of them. After all, the thicker the stone, the stronger it will be and the less susceptible to damage.
If Plywood is Not Required, is Any Support Needed for 3cm Granite?
Yes. There are four common places in your kitchen where you will definitely need to support your granite countertop even if you are using 3cm granite.
1 – Over the Dishwasher
The opening where your dishwasher goes is completely unsupported since there is no cabinet for it to rest on underneath. A standard dishwasher is usually a bit over 24 inches wide. This extra width allows for you to slide your dishwasher into place. For 3cm granite, make sure your fabricator uses mesh under the countertop at the dishwasher location. This will be all the support it needs.
2 – Bar Top Overhang
A bar top overhang typically creates an unbalanced loading condition. That means if someone puts weight on the edge of the cantilever top, it will want to rotate in the direction of the force. For this reason, you will need to add additional support for the cantilevered portion of your granite.
Although your fabricator will put mesh under the cantilevered portion of your 3cm granite, this will do nothing to help with the unbalanced loading condition. However, using some smartly-placed corbels, posts, or steel brackets will do the trick.
3 – All Other Overhangs
Worth noting, regardless of the thickness of your granite slabs, you will need to use iron supports (or something similar) for all overhangs. Without those supports, you run the risk of the overhang snapping off even from just a moderate bump from a wine bottle, for example.
4 – Desks
In many cases, the desk area is designed with an open, 3 foot wide area for leg space. According to the Natural Stone Institute, it is safe to span up to 3 feet from cabinet to cabinet with 3cm granite. However, you will still need to add a ledge to the back of the desk to give additional support. Doing this does not cost you anything, does not affect the look, and only leaves the front edge of the countertop unsupported instead of much more of the granite.
What Support Options Do I Have?
You have three basic options to support your granite: corbels, posts, and steel brackets.
Corbels are brackets, similar to shelf brackets, that create an “L” shape in order to transfer the load down from the countertop to the wall or cabinet below. You can find them on Amazon or at your local hardware store, and they are pretty inexpensive. They come in wood, steel, cast iron, and plastic.
Posts are another option that gives support from below the countertop. The supplier that provides your cabinets can typically suggest some options that match your cabinets’ color and style. If you already know what you want, these too can be found on Amazon and in your local hardware store.
If you want something less visible, steel brackets are the way to go. They, like the other options, still give your granite countertops support from below. Flat steel brackets can be used underneath the granite and overhang and are secured to the cabinet. Several manufacturers produce these flat metal support brackets. It is a very basic product. It is just a flat piece of steel with holes drilled in to it. If you want to install these, just notch a space in the cabinet and provide backing and support for the steel.
If 3cm Granite Does Not Need Plywood, Why Install 2cm Granite?
Depending on your stylistic preferences, 2cm granite can actually be better than 3cm granite even though you will have to install plywood under it.
With 2cm granite, you will be able to lay down a larger slab enabling you to have less seams than if you were to use 3cm granite. This is because with 3cm granite, due to its weight, you need to use smaller stone slabs and then join them together, thereby creating a visible seam that some find unattractive.
However, with 2cm granite, you can have one very large slab that extends a much greater length, decreasing the amount of seams you will end up with.
Also, 2cm granite is cheaper than 3cm granite, and it looks just as beautiful even if it is not as thick.
By now, you should know: 1) why the thickness of your granite matters, 2) that 2cm granite needs plywood but 3cm does not, 3) where 3cm granite needs support, 4) what support materials you can buy, and 5) why you should not discount 2cm granite altogether.
Looking forward to hearing how your granite countertops turned out!