Lot grading

The biggest enemy of a house is water, that is; water where you don't want water to be.
I will deal with water around the foundation here.

The single most effective way of preventing water from entering the basement through the foundation wall or through the floor is to encourage the water to flow away from the house before it has chance to soak into the ground.  At all sides  the ground should slope away from the house.  There are recommendations as to how many inches of slope per foot etc, but it is not necessary to memorize numbers.  Just remember that as long as you have a visible slope you likely will have sufficient slope. 

If you have water problems in your basement, check the grade of your yard.  If it doesn't have a discernible slope, or worse, if it has a slope toward the house, chances are you will be able to make great improvements by correcting the grade.  When you set out to make corrections you have the option of raising the ground level right around the house or lowering it as you go further away from the house.
 
The option which is the best for one lot may  not be the best for another lot.  Just make sure you don't raise the ground level at the house so much that moisture could get in behind the siding or soak into the bricks.  You should try to leave about 8" between the bottom of the siding and the ground level

This diagram shows a situation where raising the grade at the house isn't possible without piling the soil up against the siding.  In this case the high part has to be lowered in order to get the proper slope. (The dotted line shows the grade after the change.)

The situation in this diagram allows you both options.  You could cut the high part down or you could fill in the low part next to the foundation wall.

This all may seem like a lot of work but it is worth the effort and in most cases the cost will not be that high.
Most houses are built so that there is an opportunity for the water to drain away over the surface.  If your lot is higher all around than where the house is situated it may be necessary to drain the water via swales and an underground drainage system.  This of course gets more costly.

As an example of the effectiveness of lot grading to prevent a wet basement I'll tell you about the house I am living in right now.  We bought the house about 12 years ago.  The renters who were living in it then warned us that the basement was wet and there was evidence indicating they were speaking the truth. (I don't think the owner would have been too happy had he known that the renters were not helping the sale process.) 
Since then we have regraded all around the house and we have not had water in the basement for years now.  (As a matter of fact, the sump pump is on stand by but pretty much unemployed.)  This gave us the confidence to finish the basement. 
If your home inspector checks out your lot and the lay of the land, he is doing his job and he has your best interest in mind. 

Submitted by Bert, for Benchmark Home Inspection Services.  Your Kitchener, Waterloo, Guelph and Orangeville area home inspector.