There are several issues to consider.

Is this a concrete foundation wall?
What is the exterior of your house? Stucco/brick/siding?
Has the wall been damp proofed? (does it have a layer of tar on
it)
When you add 18" of dirt, will there still be about 6" of concrete
showing below your siding/ brick veneer weep holes?

If this were new construction and attempting the best practices,
you would:
Damp proof or water proof the walls to the top of intended grade.
Install French drain system at base of wall/footing.
Install protection board and/or drainage plane material.
Backfill with native material, preferably clay, compacted to 88%
Proctor density or better.
Top off with 3-6" topsoil
Minimum drainage grade 6" fall in the first 10 feet.
Avoid plantings and downspouts within 4 feet of the foundation.

This is not how it usually happens. The backfill is shoved in
loose and may settle over 2-3 years. Builders and home owners
plant bushes and flower beds along the foundation, then water the
day lights out of them. Most of your problem may be from this
approach. It would be best for you to remove the sod and topsoil
where you are changing the grade. Add compacted select fill
(called different things in different areas - here it would be red
select) to correct grade. Top off with your topsoil/sod or
purchase new top soil.

You can just add dirt on top of what you have, but this method may
take reworking each year for several years to develop a dense
enough subsoil to shed water. Your old sod line will rot and
decompose over several years. Top soils and loams tend to absorb
and hold water. Clays and selects tend to shed water. Hope this
helps some.
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




wrote in message
ps.com...
I posted a question several days ago about grading land
around my
house to keep the basement from leaking, and I received many
good
suggestions. I have pretty much decided to buy topsoil and do
this
myself. My question is: How do I "stack" the topsoil or add
plants to
it to make sure that it stays firm after I establish the slope
away
from the house. There is a pretty significant depression of
about 18
inches near one corner of the house, and I strongly suspect that
merely
piling topsoil in the low spots and sloping it away from the
house is
not enough to do the job correctly.

Thanks,

JD