When you are buying a house it's always a very good idea to check in the crawlspace.
Sometimes you will find white powder on the walls this is called efflorescence many times there is only a small amount close top the floor on the walls but in some cases there is lots just like this pic and if you go to the house after it has rained you may find water on the floor.
There are a couple of things that can cause this.
1- If there is no damp proofing on the concrete walls the water will be up against the concrete and if you have clay soil the water will go through the concrete and leave the efflorescence on the inside of the wall.
2- On some homes there will be no drain tile around the house this not a good thing as when there is a good down pour of rain there will be to much water for the ground and then the water will come into the house through the gap between the wall and the floor and this is one way you can get water sat on the floor in the crawlspace.
So how should this be fixed when you find this problem, the best way to fix this issue is to dig a ditch all the way around the concrete wall down to the bottom of the footing.
Once that is done you would a tar to the walls then add a dimpled plastic membrane this protects the wall from moisture and provides drainage plane.
Then all the way around the house up against the bottom of the footing you would add drainage tile then you may run it down to a rock pit too take the water away.
Once the drain tile is done you need to add gravel over the top of the pipe to make it easier for the water to get into the pipe when away from the home. then you can fill the ditches back in with the soil.
If you are not sure what to look for give us a call here at Red Bear Home Inspections www.redbearhomeinspections.com and we would be happy to give you a detailed report on your home.