A structural engineer can calculate your existing floor framing,If exposed in your basement, and come up with a correct solution.It's always a good idea to go overkill on floor framing to meet demands of higher live loads in the event you change your mind and go with heavier counters,etc. You are wanting to do the reverse by lightning up. This is fine if you will be in this home forever, but for resale, i would upgrade the floor framing.

It's a small cost to have an engineer do the calcs so I'd go there first! Our significant engineering requirements still only cost about $1000 (and a bottle of wine) to get calculated. You're going to need to do this anyway because when you work with structural issues you have to have them approved by the county/muni, whatever :)

You may not need it now...but you will when you sell, so now's the time to do it.

"It's always a good idea to go overkill on floor framing to meet demands of higher live loads in the event you change your mind and go with heavier counters,etc."

No, it is just a waste of money almost all the time.
Main floors in houses are already designed for 40 pounds per square foot (PSF) live load and 10 PSF dead load.
The joists are designed as if the entire floor from support to support of the joists has 50 PSF of load.
Very few applications ever come close to this type of loading.
A 10 foot by 15 foot room would have a total load of 7500 pounds.
Even 3 cm granite counters are not going to bother anything designed to modern standards.
A very old house may have been over spanned, but once codes came into existence the numbers have held pretty constant for many years.
A 50 year old home was built in 1957 and should have no real issues.
If you are really worried have a structural engineer come and measure the joists and spans and see where you are.

I have to agree with brickeyee. Unless the framing underneath is rotted out, or was chopped up by a brain-dead plumber or something, your present framing should handle any counter top and fridge you put on it.

If you've had a party with more than 10 people in the kitchen, you likely had at least as much load as you'll put on it with a granite counter top and big fridge.

Thanks for everyones detailed responses on my floor concerns. I appreciate the time everyone took to reply.

Could anyone tell me exactly what would most likely happen if we did put too much weight on the present floor framing? Would the floor start to sag, or would the kitchen walls brake away from the ceiling or is this just too hard of a question to really say? Just wondring if I could land in the basement one morning making toast!! Thanks again, Zoey

I should have stated "in my opinion" on going overkill with floor framing. On our build, i gladly spent the extra dinero to do this on our floor framing as well as roof framing, because as much respect i have for specs and calcs written up by engineers, i have a healthier respect for mother nature and the damage that can occur when she rears her ugly head.I would just as soon pay now than way more later!

I'm with Brick on this one, too. There's well-built and then there's overbuilt, and it shouldn't be all that difficult to figure out what you've got. The extra loads you're talking about aren't going to be moving around and flexing the structure; you bring them in and set them down, and there they stay. The sub-zero may be heavier than your average Kenmore, but it's not as if you'll be parking a tank in the corner. I know married couples whose combined weights are more than most subzero models! The granite is heavy for a person to lift, but it wouldn't feel like much if you were a house. In structural terms, the farm sink is essentially weightless; so is the hardwood floor.

The trouble with all this is that it's pure conjecture. No one can guarantee anything without knowing what you've got. What size are the floor joists? Are they spaced 16" on center? How long are their unsupported spans? What size support girders to they rest on? How well is the girder supported? It's not rocket science, but neither can it be boiled down to "Boy, this stuff is heavy! Better beef up that floor..." The numbers are worth looking at.

Wood is amazingly strong, and old wood is generally stronger than new wood. We just completed a remodel where we found a single 2x4 as a corner post where a newer addition met the main part of the house. This was holding up one end of a 4x12 beam where the addition met the house, plus a lot of the previously existing structure. It sagged, but no cracks at all.

Still, a structural engineer's fee is a low price for peace of mind. I'd bet you could bring one in for a quick site visit, and they will be able to tell right away whether the existing framing is adequate for what you want to do.

Things that appear to be very heavy are often not nearly as bad when you figure out their actual loading.
A 200 pound refrigerator that is 36 in wide and 30 inches deep has a footprint of 7.5 square feet.
The floor is designed for a live load of 40 PSF and that are would take 300 pounds to come up to the design value.
100 pounds of food just gets you to the design value, and that is in one spot, not the entire floor.

...because as much respect i have for specs and calcs written up by engineers, i have a healthier respect for mother nature and the damage that can occur when she rears her ugly head."

You are still using the engineers numbers and calculations to establish the baseline you went up from.
I cannot recall the last correctly constructed wooden structure failure I investigated.
Every one has been caused by NOT following the codes.
Did you beef up all the walls to account for the extra weight of the joists?
Houses already have rather large safety margins built in if you follow the codes.

Codes in our area are generally drawn up as the minimums on prints. I specified our engineer to calc out all structural elements to exceed codes including the walls,but not so ridiculous that it would be cost prohibitive and a waste of money by going too far overboard.Live load, wind shear,snow load calcs have all exceeded code, and is how i framed the house.The same for the foundation.