can my floor support 3cm granite countertops?

14 years ago

How do I determine if my 1970s floor joists can support a 3cm granite island countertop and perimeter countertops. I'm not so concerned about the perimeter countertops - but want to be sure about the island! Joists are 2x12, 16 on center. Unsupported span in the bedroom below the kitchen is about 11 feet. The island will actually sit on top of the bedroom hall wall below it. Planned island size is about 6 feet x 5 feet.

We have the kitchen floor partially open now (to run gas and plumbing) so I could possibly sister on additional lumber to the joists if I need it. Much easier to do now than to find out after the new hardwood floors are installed!

Thanks in advance for any tips or suggestions.

p.s., I've been reading through many of the "I wish I would have..." and "I will do this next time..." and "amazing backsplashes" posts. THEY ARE ALL AWESOME! thanks!

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Comments (4)

macybaby
14 years ago
I think your floor is fine. 2x12 over an 11' span should be fine. And if there is a support wall under where the island will go then there should be no issue at all (provided you have an adequate subfloor installed).

This is a lb per square inch issue, and even though the countertop is heavy, it is spread out over a wide area. Your fridge is one of the heaviest lb per square inch, it has all the weight over four tiny feet. It is sort of like when your cat walks on you. They aren't that heavy but when they put all their weight on one small foot - it feels like a whole lot more (especially if they step on your bladder LOL!).

Cathy
azstoneconsulting
14 years ago
you should be fine.... 2x12's spaced 16" OC is an industry standard for
flooring support..... you should have no worries

hth

kevin
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Mark_rachel, its only 12" because there is door to my backyard to the right of it and a wall that juts out behind it that would create a bottleneck if the island is too big. That's the most I can have without blocking traffic. When it was designed I wanted a full two feet behind the sink so my kids could sit there without their stuff falling in the sink. It was decided to put cabinets in the back for a little extra storage without the need for extra support. I would love to have a slightly bigger overhang but I don't have to room and yes, I want the best I can get for my money. If you could have the exact same countertop for $2200 vs. $4500 isn't that the way you would go? I'm bucking at the supports because that is what the back cabinets were put there for, supports are going to get in the way of the doors. Mainenell, that's an interesting idea! It would require adapting the back cabinets though or it would block the doors opening. Weedmeister, thanks for the warning. It is firmly bolted in. My husband built the base on site because this house is old and the floor decidedly unlevel.
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musicwife
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We're a couple who have renovated/restored 2 "historic" homes. We're intelligent; we research; we read a lot; we plan carefully; etc. But, with 35+ years of projects and renovation now behind us, I emphatically suggest, "ALWAYS get an EXPERT's advice!" A real expert.

• Houses, like our bodies, are an integrated whole - "trouble" in one small area can cause trouble/challenges in seemingly unrelated other parts. Consequently:

• We only trust certified ENGINEERS or ARCHITECTS in cases like those described above. Example: When we were considering tiling a 15'x25' kitchen floor in our 1895 house (a frame Queen Anne), we asked a restoration architect's advice. He pointed out that the floor (and joists) are connected to the walls, etc. - adding significant weight in one room can/may cause problems all over the structure - cracks in walls in other rooms, etc... Even tho' our 1890s floor joists were a full, "historic" 2"x16", he advised against it.

• A couple of years later, we wanted to add 12' of built-in bookcases in a 2nd floor library, to hold BOOKS (notjust little light-weight gee-gaws and "pretties"). Even though the proposed placement was on a load-bearing wall, we called an engineer. He drew, determined the ultimate weight of the 14" deep (and 9' tall) shelves crammed with books, punched his calculator, massaged data, and finally said we'd be OK, ONLY because the weight we were adding to the wall would be "carried" by 2 lower floors AND because the lumber in our house was "full size." He noted that lumber today is 1/4" smaller (width AND depth) - if that were the case for those joists, the additional bookcase weight MAY have been a problem.

• Restoration and remodeling is rewarding and enjoyable - good luck!
User
4 years ago
last modified: 4 years ago
This is a simple span table. L833 deflection. It’s more than fine for even putting down natural stone tile and a heavy counter.

can my floor support 3cm granite countertops?

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macybaby

azstoneconsulting

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