So we are ok on the first criteria but we exceed the 1 3 criteria by four inches.
Quartz countertop overhang without support.
Amount of overhang you have is the most important factor to consider in deciding whether you need support brackets.
Because not every bracket is the same certain support brackets may be too weak to hold stone like marble granite or quartz.
Yes you can extend the overhang on a kitchen island countertop.
3 cm quartz engineered stone can handle a 14 inch countertop overhang without additional support 3 cm granite overhangs should not exceed a 10 inch overhang without additional support bearing in mind the 70 rule.
However once you gather your information and find out from the installation guide for your material you will then be better prepared for selecting countertop support brackets that are designed for your purpose.
In conclusion the answer to the question how far can quartz overhang without support is.
That said there are standard dimensions that can help guide you as you plan out your kitchen remodel.
Even leaving your brackets weakly fastened leads to inadequate countertop support.
Once your countertop overhang exceeds these numbers it will require additional support through corbels base cabinets or knee walls.
That depends on many factors regarding the project material and the thickness of the surface.
Overhangs greater than 15 require the installation of corbels.
The allowable overhang with no additional support is no more than 1 3 of the depth of the countertop and not to exceed 15 total.
As the chart indicated solid surface countertops may only overhang 6 inches without additional support.
The following recommendations help determine the needed support for quartz countertop overhang installation.
However you may need to install supports such as corbels or legs.
However the cantilevered portion cannot be more than 1 3 the total width of the countertop.
According to the marble institute of america you can safely overhang granite that is 1 1 4 thick up to 10 without supports.
Countertop overhang will depend on various other measurements such as the countertop itself and cabinetry.