Drain tile installed on the footing vs. next to the footing
It is technically better to install the drain tile off, or next to the footing. But, it is also better to use a 1,000 pound chain when installing a swing. But, will you ever need a 1,000 pound chain? Would a 700 pound chain do the job? In most cases, yes. But, a 1,000 pound chain is still better, right? That is the basic logic behind installing drain tile off, or next to the footing vs. installing it on the footing.
It takes more labor to install the drain tile off the footing. The reason is because the ground next to the footing needs to be prepped. Trenching with a shovel may be necessary to ensure that the top of the tile is not above the footer. Concrete overspill from the foundation may need to be removed. Additionally, you should not lay the tile directly on the dirt, so a 2” minimum bed of gravel or filter fabric should be installed first.
Installing drain tile on the footing is much easier and requires less labor. You simply sweep the footing and it is ready for drain tile installation.
You can expect to pay about $ .75 – $ 1.00 per lineal foot more to install a drain tile next to the footing vs. on the footing. You will also have a little more gravel to pay for. This equates to about $ 200 more for an average sized home.
Is it worth the extra $ 200? Having an understanding of how water enters a basement is the key to understanding if it is better to install it off the footing. The drain tile system is designed to keep the water table from pushing up on the bottom of the basement slab. If you can imagine the water table doing this, you can get a clear picture of how it works. During rainfall events, the ground beneath the home becomes so saturated that the water table rises like a lake upwards towards the floor slab. The water will take the path of least resistance. A drain tile system should be this path of least resistance since it is installed at a level that is lower than the floor. But, is lower better?
If your drain tile system is installed next to the footing, it is lower than a drain tile that is installed on the footing. So, it will be able to pick up the rising water table sooner. It manages the water approximately 4” – 8” sooner than a drain tile that is installed on the footing. (this can vary depending on how much trenching is done)
But, drain tile installed on the footing is still installed at a level that is lower than your basement floor so it still works. Drain tile installed on the footing will allow a water table to rise closer to your basement floor. But, as long as it keeps it from penetrating the floor, does it matter? Well, in some rare cases, a water table can rise so fast that it overwhelms a standard drain tile system. In those cases, it could be beneficial to have it lower.