Can my floor support Kitchen Island?

Question

I am installing a 5' x 3' kitchen island consisting of two base cabinets. Once I've installed the two base cabinets, SilestoneUSA will install a quartz counter top.

My plan is to screw two parallel 2x4 blocks/cleats to the floor, then screw the cabinets to the cleats, as pictured here:

source: Step #6, photo #11 of Installing Kitchen Cabinets

Given the layout of our kitchen, the cleats will run parallel and in-between joists. This way the screws I drive through the cabinet into the cleats will be hidden by the toe kick. These cleats will be screwed 8" to either side of one joist. Once everything is finished, I think most of the load be distributed on a portion of the hardwood floor ultimately supported by three joists... although full weight of the cabinet & counter will mostly be distributed in-between one joist!

The kitchen has a hardwood floor supported by 2x8 with 16" centering. The 2x8's span 11'6". The 5'x3' (15 sq ft) quartz countertop weighs about 18 lbs/sq ft. Can my floor support the weight of the counters?

Here's a picture of my plan:

2x4 cleats will be drilled into floor. Masking tape marks approximate location of 2x8 joists spaced 16" apart.

Answer 1

The counterop weighs less than 300 lbs. The cabinets probably weigh less than 100 lbs. This is about 400lbs spread over a floor area of almost fifteen square feet. this is less than 30 lbs per square foot.

An adult standing still is about 150 lbs on one square foot.

You should have no problem with the load regardless of the placement with regard to the joists.

Answer 2

One option is to screw cleats perpendicular to the joists.

Benefits:

• load of the cabinets + counter will be more evenly distributed on 2x4's which are perpendicular to joists.

Downsides:

• I will have to screw the base cabinets through the sides of the island. This way, screws will be visible. When the cleat is parallel to the joists, my kitchen layout will allow me to screw through the toe kick on the cabinets, making the screws less obvious.

I'm not really sure if this is the way to go, any comments/suggestions?