Water intrusion through penetrations is the entry of water through punctures made by plumbing and electrical lines in the vapor barrier.
Water can rise in vapor form through the soil and gravel layer into the slab. The gravel layer prevents bulk water from entering the slab. To prevent water vapor from entering the slab, a 10 mil vapor barrier is placed on the gravel layer.
Punctures in the vapor barrier
When the vapor barrier is installed by the foundation crew, the crew has to puncture it to fit it around the plumbing and electrical stubs that have been installed by the plumber and electrician. These punctures, if left unsealed, leave a pathway for water vapor to enter the slab through the vapor barrier. Water entering the home through the slab can wet carpeting, vinyl, and tile grout, potentially leading to mold growth.
Cause 1:
Failing to seal the vapor barrier around penetrations
When a plumbing or electrical line penetrates the slab, it punctures the vapor barrier. This puncture provides a pathway for water to enter the home. If the foundation crew doesn't properly seal the vapor barrier at this puncture, water vapor moving up from the ground can enter the slab through the punctured area.
Solution
Before placing the foundation concrete, properly seal the vapor barrier around penetrating plumbing and electrical stubs. When installing the vapor barrier, make an X-shaped incision in the vapor barrier, and fit the vapor barrier over the stub through the incision. Next, cut out a 4'x4' section of vapor barrier material. Make an X-shaped incision in the 4'x4' square that's just large enough to fit tightly around the plumbing or electrical stub. Place the square over the penetrating stub; the square should lie flat on the vapor barrier. Then, tape the incision around the stub.
