I guess I misunderstood this sentence from "Understanding Basements": "A sheet polyethylene vapor barrier should be located over the rigid insulation and in direct contact with the concrete slab." I saw "over", "direct contact" and "concrete slab" and understood that to mean that the barrier should go on top of the concrete, as many would recommend. I read it more closely and see that it recommends to avoid an interior vapor barrier. What is the best way to install the laminate if I am not in a position to install 1" of XPS and two 1/2" layers of plywood? It sounds like there is no ideal way but I would like to know which method is least likely to cause an issue. Thank you.

I had a similar problem (actually the same but opposite...had to dig to bedrock because my 99% silt soil has no bearing capacity, and ended up with my basement being too deep, and had to raise it back up with gravel). I did call in a structural and geo engineer (looks after large projects in my city for things like building malls on soupy clay soils), and he determined all the granular fill, compaction and footing sizes based on that. We also, had the soil not been so rocky, had the option of installing piles as a base to help stabilize the foundation. So yes, by and large it can be done, but I would agree with the others and say you really should consult someone with a great deal of knowledge on this. (especially if like me, you wind up with the process halted by the BI when they're not familiar with the soil structure your dealing with...and your engineer is the only person who can stamp off on the structural integrity and get the process moving again...)

Is the entire area 3 inches low? That is enough to use concrete on. If the area will be covered with a finished floor (carpet, tile, etc) you can get away with more. You might fill it with concrete for a few inches and then top that with leveling compound, or just strike it off level withthe existing area. Shallow fill creates problems with the size of the aggregate that can be used in the concrete. If you are willing to use Sakrete or other small fill material you can go to about 3/4 of an inch and still obtain a good surface. If the existing floor is in good shape in the area, you are not ooking for strength so much as adhesion to the previous floor. There are a numbe of 'glues' for improving the adhesion of one layer of concrete (or mortar/grout) to the old layers.

Top of the basement floor should be min 12" above seasonal water table. You want your pump to be deep and as close to the water table as possible. Try a better pump that can pump more water, you don't want your water level to be so close to the slab.