The Sill Plate is the boarder beam that is directly connected to the rest of the Cross Beams and rests on the tops of the foundation. Sometimes it is built flush with the outside of the foundation wall, and sometimes it can be centered. Like the side boards of a deck it’s meant to help square up the cross support beams and distribute part of the weight down the foundations directly. The rest of the distribution of weight is taken by the massive house support beams (normally found in the center of the basement ceiling) which can then have 1 to many support columns which are metal poll that support at possible weak spots in the house support beam.
Now that you have an idea of what you’re looking at above you lets get to the bottom of this.
If water is coming in through the top of the foundation, ether through an opening in the sill plate, over the sill plate, or under the sill plate, it typically means one of two things.
1.) That the land graded to the foundation is too high and coming into direct contact with the sill plate. Sometimes allowing water to collect and drain into the basement.
2.) That the whole area has experienced major flooding where the water level has risen to meet the sill plate directly or risen above it.
Now the typical rule for grading land is so that when the back-fill is placed after the formation of the foundation walls, that the grade of the land doesn’t meat the foundation any higher than 6”-12” down from the sill plate. This isn’t just for water.
The main reason that this rule was placed was because of insect and animal access. It’s harder for termites to gain access to the sill plate so far from the soil.
If you are experiencing this problem outside drainage can help, however it won’t solve this issue (especially in the cases of massive exterior flooding.) The first thing that I would recommend would be to get in contact with the builder of the home and discuss solutions to your property. If you can’t a hold of the builder, don’t know them, or live in a much older house then contacting a landscaping company to help you with the land grading would be your best first star in solving this issue.
This type of jump is most typical in these conditions listed above. People who live in houses with no basements, their houses being placed on slab, will also see direct correlation into their “first floor” living space. If you don’t know what type of foundation that you have and would like to find out you can go to your town hall and request the plans for your house, they’ll be able to direct you to exactly where you need to go for this information.