When it comes to pouring and detailing a foundation slab, you have one shot to get it right—at least without the major expense and headache of a retrofit. Correctly detailing the control layers for water, airtightness, vapor, and thermal management is integral to the assembly’s successful performance. This is our approach to constructing a basement that will stay dry and in a healthy condition.

Water management always comes first

Under-slab water management requires what we call an exclusion tactic—meaning preventing water from collecting right from the get-go. It is achieved with a perforated perimeter drainpipe. In this detail, the pipe is installed to the interior of the footing. It is not uncommon to put it to the exterior of the footing or to have one in both locations. What determines this is the level of risk given the local water table. The higher the water table, the higher the risk, and therefore it is advisable to have more than one path directing water away from the foundation.

如果只使用一个排水管，你是否将其放在脚踏的内部或外部无关紧要，只要管道安装在板块底部下方。另请注意，穿孔漏极通常设定在石头床中以促使水横向移动，进入排水管，从而将其转移远离板坯。石床也充当毛细血管休息。如果石头和周边排水管正确安装，板坯的底部不应在其寿命中看到水。

Lastly, there are two places water can exit the pipe. If the site is sloped enough, the pipe will drain to daylight down grade. If the site is closer to level, the drain…