Removing underlayment from around a large kitchen island

[FiteClub]

Hello! I would like to replace my exisitng kitchen tile with hardwood. In order to do so I need to remove the underlayment that is on top of the subfloor. I am not concerned in the process of doing this, but my question lies in the weight of our kitchen island. If I remove the underlayment from around the 9-foot kitchen island with a quartz countertop, should I be concerned with the weight of the island no longer being distributed onto the tile and underlyment that runs beneath the island? Will this put undue stress on the joists below? Do I really need a structural engineer here? Or to remove the entire island and run the hardwood under the island?

For reference, I am not worried about the height difference of the tile and the hardwood. Once I remove the tile and the underlayment, the hardwood will butt up against the old, exisitng hardwood in the rest of my open floor plan. I've removed a tiny little section in order to investigate what is below the tile. Thanks!

 

[zannej]

The floor underneath should have been of sufficient strength to support the island no matter what type of flooring was on top. Pictures might help to see what you're talking about (if you're able to upload them) so we can see what you're dealing with.
Is there any reason you wouldn't leave the tile/underlayment just under the island? Was the island built on top of it & are you sure it wasn't built around the island?

 

[FiteClub]

Hi there, I will upload some pics soon. Yes, the island was built on top of the tile and the underlayment. I think it would be fine to cut around the island and leave it on top of the tile but my husband is concerned that if I cut the underlayment around the island to install hardwood it will somehow mess up the load of the island...

 

[zannej]

So, are you worried the countertop on the island will crack & that the island itself won't be supported rather than the floor not being able to support the island?

The island should have been constructed so that the frame supports the top. I can't think of why the island would be undermined if the surface underneath it remained.

Was the plan to move the island to remove the tile & underlayment & then put new floor underneath?
Or remove the floor underneath & put new floor around it?
I can't think of any reason why cutting around the island would change the load, but perhaps pictures might help. You might also try asking in the houserepairtalk.com forum (a sister site to this one) since it involves a kitchen island and not just floor.

 

[havasu]

A 9' long Island, with a minimum of 2' wide, is 18 square feet. What do you think it weighs? 1800 pounds? That is 100 pounds a square foot. If I stood on your floor, with feet side by side, you'd be looking at 250 pounds per foot. Does your floor flex at all now? For safety sake, can you look under the sub floor and look at the bracing?
IMHO, I'd cut it and place the floor around it. Or just get 4-5 guys and move it out of the way, install floor, them move it back.

 

[zannej]

If you have to pay someone to move that island it is probably going to be expensive. Flooring installers should (and probably will) charge for moving something that large & it will take multiple people. More chance of stuff breaking it if it is moved. I'd take Havasu's suggestion and cut around it. Also, he mentioned the floor flexing-- if it flexes or sags under the island, you may want to add more supports from below the floor-- run some cross-braces between the joists.