Why does the ground settle around my foundation?
As I sit here waiting for my shift at a local trade show we are doing and having just come from an estimate this morning that also needed to have backfill added to their foundation. I realized that I get asked this question A LOT, why does the ground settle around the foundation? I will do my best to answer without the need for diagrams.
First when a house is being constructed it generally has to be dug out for the foundation/basement walls to be installed. When doing this the ground needs to be dug out 2’ to 5’ deep, depending on the contractor, in order to be able to have the necessary room to work. Once the walls are constructed they are waterproofed and drain tile put in around the outside perimeter, then back filled with some of the dirt that was excavated.
When this soil gets placed back in the hole it usually is not compacted well and certainly is not compacted back to its original density rate which is dependent on the makeup of the soil and geographic location. Over the course of the following years water that saturates the earth will compact the soil trying to achieve natural state. This can mean a settlement of very little to 12” of settlement. A lot of people will blame the builder and shoddy work. Although a lot of times they can slow down take more time and results will be better, most of the time it’s just the law of physics and just not practical in the building world to wait 28 days for concrete to cure before compaction filling.
This settlement naturally will affect things that are directly on top of it like driveways, sidewalks, patios, curbs, any type of concrete slabs or landscaping that is installed on top of the area. Another thing that affects this negative slope directly is the gutter downspouts. If they are unable to drain water effectively away from the foundation then the water settles and saturates the ground close to the foundation walls causing the water to compress the soil and sometimes erode the soil even more.
The soil grade being maintained at a slope away from the foundation can save many foundation repair bills in the future. Most of the time by the time you recognize the problem it’s too late. Keep the surfaces concrete and dirt alike sloping away from your foundation at all times and keep the downspouts maintained to drain water far enough away.