Moisture Intrusion is one of the biggest problems a home can have. Excessive moisture can cause rot, insect infestation, water damage, mold - well you get the picture. One of the real challenges with moisture is that there are so may ways it can get into your house. Think about it, on the one hand we create an envelope to keep moisture out. Then we penetrate that envelope to bring moisture in (water lines). And all the while we humans are breathing , cooking and showering creating even more moisture.
Checking for possible ways water can get into you house begins outside. Does the land slope away form your house or towards it? Look at the driveway and see if it slopes away. Are there planting beds that hold water against the house?
Look at the down spouts, do they dump water against the foundation of the house or do they direct the water where it will flow away from the house? Does the downspout go underground and into the foundation drainage system? If so this puts water against the foundation and if there are any breaks in the drainage system water will be deposited against the house.
What about the siding? Is it intact or are there breaks in it? Check the doors and windows for areas that need to be caulked. Take a look at the roof. Is there flashing at the chimney and other penetrations (stack, vents, and gas appliance chimney)? Is the flashing properly installed? Does the roof slope enough to shed water or is it too flat? Is the roof clean or are there areas where leaves have stacked up. These leaves will slow down water flow allowing it to back up and soak thru the shingles. Leaves also hold moisture against the roof which can cause problems.
If you think you have found problems you should take actions to fix them. Water can destroy your home.