Uneven floor joists....installing new floor covering...2 problems.

Hi all,
I am looking for a bit of advice on how to fix a flooring problem. I want to install some new flooring (good vinyl or laminate) in my kitchen. The cupboards/counters form a U-shape around the problem area, which is about 5' by 10'. 8" Joists are running parallel to the 10' section.
Although I haven't done any extensive measurements, it appears that two of the joists have a slight arc and are slightly higher than the surrounding joists. It is possible that the surrounding joists are too low. In either case, I have a wide hump across the floor. This may be ok for vinyl, but it isn't suitable for laminate/ceramic and certainly isn't very aesthetically pleasing.
To fix the problem, I am considering removing the old vinyl (house is about 6 years old, but the vinyl is in horrible shape), cutting away the 5/8" plywood subfloor in the problem area, and manually planing down the offending joists. Because it is such a small space, I cannot remove the full sheet of plywood without first removing the cabinets/sink/etc....which I definitely do not want to do at this point.
I was thinking of using a reciprocating saw to cut the subfloor from below (exposed joists in the basement). This would allow removing a section of the subfloor without ripping up an entire sheet of plywood. Once the joists were "corrected", I would drop in a piece of plywood (cut to fit). I plan on tacking up some 2x6 to the joists (flush with the top) to provide a solid surface to screw the new subfloor down.
Finally, some levelling compound of some sort might be in order.
My 2nd problem....the floor doesn't seem to be particularly solid....jumping (or simply 'bouncing' without leaving the floor) causes items in the room to shake....particularly at the top of a tall bookcase in the room. I am concerned that this might prevent me from installing laminate/hardwood. I am considering adding an extra 3/8" surface to the entire area (approx. 400 sq. ft.), but don't know if this will buy me anything in terms of a more solid floor. Any opinions? As I said, joists are 8", and the span is probably 10'. I could do some cross-bracing of the joists from below, but again, I don't know if that will result in a more stable floor.
Thanks in advance, Dave
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umm remove the old floor covering , get some levelling compound and poor it onto the floor, wait for it to dry install new flooring.
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You did read the part about the floor flexing? Self leveling compounds have many limits and this would be one of them.
J.P.
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Cut your plywood first and use it as a template to cut the floor from above. Use a circular saw that is adjusted to cut just deep enough to cut the plywood floor. Cut just inside the lines you drew.
You didn't mention any underlayment. Do you have any underlayment?

Are they at 16" or 24" centers? Sounds like the contractor may have gone cheap. You may need to either nail extra 2x8's on the side of the existing boards.
-- Mike D.
www.stopassaultnow.org
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Mike,
That sounds reasonable, and was actually my first idea. I mentioned using a recip saw from below because of the (potential) close proximity to the kitchen cabinets. I am left-handed and tend to shy away from circular saws as a result...but I'm sure I can make an exception in this case.
The joists *average* 16" centers, but that could vary by an inch or two depending on the joist....and there's no doubt that the contractors went cheap (and fast). It looks like there's about 1/2" elevation change over the span of 4'. Levelling compound just won't cut it (I think).
I checked the rest of the floor, and there are some minor variations (maybe 1/16" - 1/8" over a 4' span, depending on the direction. I hope that a levelling compound *will* be able to compensate for this, but I need to do a bit more research.
There appears to be nothing but 5/8" plywood nailed to the joists. No other membrane or layer that I can see (so no underlayment).
In terms of stability, should I put another layer of subfloor down (maybe an extra 3/8" to 1/2")? If so, I guess I should apply a levelling compound first to correct the minor variations, then add the plywood, and possibly more compound after that....I think this may get expensive!!
Cheers, Dave

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Dave,

Just a side note...
Like you, I'm corrie-fisted. Last spring I built a deck - actually rebuilt and expanded to two levels the deck I had. Lots and lots of circular saw work. Best thing I ever did was take some scrap out of my bin and get comfortable using the saw with my right hand. I really surprised myself at how fast I made the transition - I did the same thing with pounding nails - and I can now, with a refresher on a scrap or two now and then, use the saw with either hand.
Best,
- Wm
-- William Morris, Tailor Seamlyne Reproductions http://www.seamlyne.com
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