Solid Hardwood, Engineered and Laminate Flooring - HELP - Concrete prep for laminate + underlay

Thanks for reading this and any help would be really appreciated!!! I have seen posts on concrete prep for hardwood, but not for laminate (maybe I missed it though). Just bought a 30 year old house. I'm redoing the basement. Basement had a rental suite, I am remodeling it. Need floor advice!!

- I pulled up all the old carpet..2 areas of interest, one 10x12 foot area had tile and they filled it in with some compound (not very level though) and another 10x12 foot kitchen area has linoleum.
- Total Area: 500 square feet concrete basement, u-shaped space with stairwell in the middle
- 60% of floor perfectly level!!
- One area has some major cracks and my 4 foot level indicates 1/2 - 3/4 inch gaps. There used to be a small dividing wall there and they removed the wall.

Questions:
- The previously tiled and partially filled-with-compound area: Should I try and level it some more with a cement/levelling agent? There are small bumps everywhere and I'm not sure if the foam can 'absorb' these irregularities.

- Do I need to feather the edge between the lino and concrete floor with compound so there is no drastic gap? (note: this is minor compared to other trouble areas)

- The one big 5 foot x 1 foot bulge, how should I level this out?

- Is there a rule of thumb for acceptable irregularities for laminate + foam? i.e. I saw 3/16 inch per 6 foot radius posted for hardwood...

thank you!!!

Howdy. If you'll go to the top of this category, you'll see a sticky that addresses this very issue to which carpets done wright responded. He does an excellent job of explanation, complete with pictures. Give it a look and then, if you still have questions, ask away. We live for answering questions.

Well, perhaps not "live", but you get the idea.

Thanks for replying Smokey49!!!!!

LEVELLING:
The thread you pointed me to talks about adhesive/glue and looks like they put hardwood right on the concrete and in that scenario I can totally see the need to have the concrete completely level. The product I am installing is the click laminate and no glue, so I am not sure how truly level I have to make the floor since there will be a foam layer under it. There are lots of little bumps everywhere where the tiles used to be and not sure If I have to cover that whole area with a levelling product/compound or if the foam absorbs (so to speak) these imperfections.

UNDERLAY PLASTIC OR NOT OR 2-IN-1
Other: what about the 2 in 1 faom plus plastic versus separate plastic layer and then foam - A freind told me Holmes on homes says NO plastic because it traps the moisture - UG - wheras some tell me you need the vapour barrier

The flattening process he describes is the same for laminate. The joints where the individual planks snap together do not tolerate flex or movement. Too much and they will actually disintegrate at the locking mechanism and the floor will fail. The underlayment is referred to as pad, but is not the sort of pad most folks are used to as in carpet. It's purpose is not to pad or soften the floor, it's to deaden sound as the floor is walked on. Consequently, it tends to be fairly thin and somewhat stiff and will not hide imperfections in the floor prep. As he says in his instructions, grind down the hills and fill in the swimming pools. You'll need to remove any old thinset humps and fill in any low spots. Various manufacturers have their own flatness requirements so you'll need to refer to your instructions to find out what yours are, but all of them are pretty snotty about honoring warranties if this is not adhered to. As to the pad and moisture barrier, the advantage to the two-in-one is that it eliminates a step. You install both at once rather than each individually. The "plastic" you refer to is a moisture barrier and, again, read your material's instructions. I have yet to see a laminate that doesn't require one.

Thanks for your clear instructions!!! much appreciated Yeesh - I've got some work ahead of me!! I did do some grinding before I drywalled, mudded and painted the walls (I've hung upper kitchen cabinets already)....looks like another round of concrete dust EVERYWHERE. I was hoping to avoid that mess again. I'm a newbie and this leveling will take me a while - I'll read tips on the leveling products again. The folks at Rona and Home Depot give me different advise depending on the person working that day... I prefer the message boards - - - thanks smokey49!!