The footing drain debate is always a point of contention between contractors and Architects.
Footing drains is piping and stone at the bottom of the footing on the outside of the building to keep the hydraulic pressure from forcing the water into the building where water table could become higher than inhabitable space below grade.
The Contractors contend that if the ground it sandy footing drains are not needed because sandy soil dissipates the water rapidly. While the Architects contend that all buildings with basements or habitable space below ground need footing drains.
In our area there is a lot of clay and rocks in the soil, so it is good construction practice to install footing drains on all buildings with space below grade. In a large building the Design professional will give the contractor specifications to go by for footing drainage, but on homes usually the contractor will install a 4 perforated pipe with a morafy cloth sleeve ( a cloth that stops sediment from getting into the pipe but lets water through the pipe) on the pipe to stop sediment from getting into the pipe and clogging it up.
The footing drain goes around the foundation at the center point of the footing vertically, with stone under it and covered over it. The drain can either be run out to daylight, into a properly installed drywell filled with stone or storm water collection system.
The stone at the bottom and over the top of the drain helps to filter the sediment out of the water. The Drain to daylight means that there is enough pitch on the drain about 1/8 to the foot to get the water away from the building and drain out of a ground and a perforated drain cover should be installed over end of the pipe to stop small animals from nesting in the pipe thus clogging it.
Drywells are calculated by how much water that needs to be dispersed. We usually figure a drywell of about 5 cubic yards with morafy cloth around it to stop sedimentation. This drywell should be as far as possible from the foundation and lower than the bottom of the foundation the drain pipe too it should have at least a 1/8 pitch per foot.
Storm water collection system is usually used in large construction projects, but can be used in smaller projects if the collection system for storm water is in the vicinity of the building project. This system consists of a series of manholes and piping to disperse the storm water sometimes into a holding pond or low area.
So as you can see it is very important to have a good footing drainage system around the buildings that are constructed even though the contractor figures that the soil will disperse the water without it. If the contractor is wrong it is very costly to install a proper footing drain system after the fact. What has to be done is the foundation has to be exposed to the bottom of the footing and one of the afore mentions footing drain systems installed, then the foundation needs to be backfilled again removing the spoilage that cannot be used on site.