Kitchen Island Support

6 years ago

We are remodeling the kitchen in our 1820s farmhouse, part of that remodel is a new kitchen island (8x4'). The room is 18x16 so I am wondering if I need extra support in the basement for the island island weight (quartz countertops). This is a picture of the beams in the basement. They are quite thick and heavy duty (about 10''x6''). Do you think I need more support then what these beams offer?

Featured Answer

Seabornman

6 years ago

If you run a string along length of the span you can get an idea how much your sag is. 16 feet is a long span for what is there. If it were me, and I'm making a few assumptions here, I'd sister 2x10s to the sides of those joists. Or I'd put a support beam and posts at mid-span in the basement. The biggest challenge is trying to get some of the sag out, if it's there.

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Comments (7)

alheff1231
Original Author
6 years ago
The island will be running perpendicular to the beams as well
User
6 years ago
last modified: 6 years ago
The kitchen and whole upper floor as a whole needs extra support. Deflection is your enemy, and those are oriented the wrong way to have good strength against deflection. You can see the sag even from that photo. Call in a structural engineer.
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Seabornman
6 years ago
What is the span and spacing of those? Does your floor move when you jump up and down? If 8 people can stand in the spot where your island will be and it doesn't deflect, you're island probably doesn't weigh that much (unless you dance on top!).
PRO
Joseph Corlett, LLC
6 years ago
Your house has stood for 200 years: it's not going to be ruined by a kitchen island. Get an experienced framer if you're concerned please.
alheff1231
Original Author
6 years ago
The beams span the full 16' of the kitchen length and are spaced 18'' apart. Overall the floor feels sturdy when walking on it, the one or 2 spots of noticeable sagging the floor boards might move a bit but its not the beam itself moving.
User
6 years ago
last modified: 6 years ago
Deflection that you can’t even feel is enough to crack tile, and be a problem supporting what you want. It has zero to do if the floor “feels” bouncy or not. The 6” height is the problem. That’s weak. There isn’t a deflection calculator that I can find that can account for your specific structure. It’s an oddball. But with only 6” of height, it’s far weaker than you think. The height should be taller than the width, in order to carry the most load. And it’s already sagging. That’s a problem, and you haven’t added any extra load.

A couple of hundred for the engineer’s visit to examine how well the joists are seated at both ends, what supports them there, to see how much it’s sagged, and to see what species it is, and in what condition, is worth the money for the peace of mind. These aren’t things visible from pictures on the internet. All of that is a factor in it‘s bearing capacity.