mAgnoliAg said:
Rain and above ground irrigation don't reach deep soils underneath the foundation.
You are wrong, but I guess we can agree to disagree.
Soil moisture increase in the wetter seasons. Despite grading, the rainy cool seasons increase the moisture under your foundation even though the rain does not hit it directly. The moisture seeps under the foundation. Drip lines are located outside the perimeter of the foundation. They don't push water under the foundation. They simply soak the soil slowly around the foundation. It "soaks' both inward and outward. Rain does the same thing, MUCH more effectively than any irrigation system.
Again, drip lines fight evaporation and dry conditions by slowly adding moisture close to the foundation. Evaporation and dry conditions are generally not problems in the winter. Even a long dry month in the winter is not going to be a problem.
The goal for a healthy foundation is maintaining consistent moisture levels around the footprint of the foundation and consistent moisture levels throughout the year despite drastically different weather conditions. Your foundation moves and a major factor in it moving is moisture levels. You are simply trying to control and limit the amount of movement caused by moisture variations. You have grading away from the foundation and gutters to keep excessive water from pooling against the foundation in the winter/wet seasons - ie control moisture when moisture is high. You have irrigation to add water in dry / hot seasons. Above ground sprays absolutely do help add water to your foundation. They are just nor as efficient as drip lines and they are subject to strict watering restrictions that have become necessary in North Texas due to lack of planning, population explosion and lack of reservoirs. So drip lines and soakers are a great idea
But, hey, if you want to waste water and money by running your sprinklers and drips in the winter, go for it. You probably won't hurt anything. It amazes me how many people I see watering incorrectly and way more than they need to. It is a huge problem in North Texas where we don't have near enough water supply.