...From your yard!
from the ground "up."
Now--if a downspout is clogged or broken, it can't carry water away from the house, which is its function. As a result, the ground around the foundation quickly becomes oversaturated. Moisture is absorbed by the foundation walls, making for a damp basement, and may cause the masonry and adjacent wooden structural elements of the house to deteriorate.
Another, more sinister, kind of invader is called "rising damp." Generally the result of high water tables or a constant source of dampness under the footings, you have probably seen a stain on masonry houses, often reaching 2 or 3 feet above the foundation. It really looks ugly. But don't try to apply some kind of waterproof coating to the wall. It only makes things worse! Improve the drainage, or, if that doesn't work, have a physical barrier, such as a slate course or plastic sheeting, professionally installed.
Sometimes further investigation is needed to get a dryer foundation. There may be underground wells, cisterns, abandoned pipes or other "hidden holders" of moisture. Tidal areas may have a history of chronic ground moisture, and there are seasonally high water tables to deal with as well. If regular maintenance procedures don't rid your house and yard of moisture problems, then more extensive remedial work will need to be done.
What to do--or not do.
The best advice is to use common sense maintenance procedures to eliminate standing water and increase ventilation of the basement, or to correct existing high moisture levels, if necessary. Here are suggestions to keep the invaders under control.
Foundation and Yard: Eliminate low spots around building foundations. Clean out existing downspout boots twice a year or add an extension to leaders to carry moisture away from foundation. Do a hose test to verify that surface drains are functioning.Crawl space: Check the foundation grilles to be sure they provide enough ventilation; vents may need to be added if there are none.
Reduce moisture used to clean steps and walks. Eliminate the use of chlorides to melt ice, which can cause damage to masonry. Check the operation of irrigation systems, hose bib leaks,and clearance of air conditioning "drip" drain outlets.
Or, a more expansive drainage system may be installed to direct water away from the house and into the yard.
Close grilles seasonally in winter, if they are not needed, or in summer, if hot humid air is getting into air conditioned spaces.