Maximum load and floor deflection depends on the type of floor joists as well as depth of the joist, spacing, span, blocking, supports etc.

we just purchased a used DW permanently set up and I plan to have granite TILE counters - the tiles are thinner than the slab, you can use colored grout (and the grount lines are fairly thin) seal the grout really well and you have a lot less weight than the slab (which I have in my current home). I also plan to replace the carpet with something else. I had a SW 30 years ago, but the DW we just purchased is quite an improvement. I also plan to replace the tub in the master bath - Carolyn

Even in the existing, and new construction stick built home market, many floor tile jobs are borderline at best as far as floor deflection is concerned.

Below is a tile and natural stone floor deflection calculator that will let you know if your floor joist depth, spacing and span are in the ballpark.

Here is a link that might be useful: Deflect-O-Lator

Materials such as hardwood flooring and tiles are spread out over such a broad area as to be minimal. Visitors in need of a good diet, by placing considerable point loads on a small area, are putting much more strain on the floor structure of your home than the heaviest flooring materials ever could.

You are correct that good sub-flooring is important.

Wayne

I worked for a custom home builder and I can assure you that the majority of our subfloors were exactly the same material as in newer DWs (I have one that I'm remodeling and upgrading). As long as you use half inch backer board for floor tiles, you're fine. As far as granite counters go, barker_tx's recommendation was spot on although I wouldn't hesitate to go with a solid slab. Here's why: the beauty of owning a DW on a concrete slab is that you still have easy access to your underside. If you are in doubt about the weight of something, it's easy enough to add cement blocks or floor jacks before making any changes, just for peace of mind. I've crawled under our home many times and noticed that that's exactly what the installers did with our jacuzzi and tub/shower unit. Also, you have steel beams for floor joists (at least we do with our Pinegrove) and they flex less than wood.
We have already replaced our living room flooring with white oak hardwood with no problems at all. We went with a floating floor, did it ourselves in a 3-day weekend and couldn't be happier. When we were shopping for flooring, we were lucky enough to encounter a salesperson who was knowledgeable and he did not recommend nail or glue down in a DW if you are spanning the entire width because they move (at least that's the case in New England). It made sense to us because our DW does move significantly during the fall and spring when the frost is building in or receding from the ground. Other than our dogs toenails, we've had no problems with our wood floors. Good luck and have fun with your remodel twhite!

I would like to lay 1000 sq ft of hardwoood in our new 1640 sq ft DW. It is on 32 block pads (forgot teckie name:. We are in a Zone 4 climate. The underlay is 5/8 plywood.
We are looking at tongue & groove that would need to be nailed. They recommend some kind of "craft paper" between subfloor & hardwood.
Any feedbac would be welcome.

We have a 2000 dw and we have installed 3" red oak flooring in our home throughout. It is the tongue and groove kind and we used a nailer and mallet to lay it. It has held up great and we have no problems except for occassional squeeking in some areas but not alot. We layed roofing felt down on top of the subflooring. We absolutly love it. Now I am about to go crazy with the ugly strips. I just don't know what route I want to take with it. We have worked on a budget and I painted my ugly white countertops black and put up a ceremic backsplash above my stove which looks great. I will post pictures after Friday...Stainless steel appliances will be in then.