Waterproofing Pipe Penetrations

Pipe penetrations are often placed by the plumbing and electrical contractors in such a manner that it is impossible to properly install the required flashings. Many times the waterproofing contractor will find pipes less than 6 inches apart, or they will be resting on the footer instead of 6 inches above it. Sometimes a concrete box must be cast to extend and separate the pipes. Spacing of these items — including the sheet metal ducts and vents — should always be delineated fully on the drawings with the understanding as to the probable physical size of the flashing to be installed.

Oftentimes the designer relies on the mechanical equipment supplier for flashing design details at the legs of the equipment supports without consulting the waterproofing contractor. This often results in having equipment supports resting on the waterproofing membrane without a pitch pocket or flashed-in wood sleepers. This typically results in leaks. The resulting leaks are not the failure of the waterproofing materials but rather are due to a lack of proper general supervision or inspection.

When providing details at supports the following procures should be followed:

1. Apply proper waterproofing system over substrate.
2. Set butyl tape in a ⅜ -inch by 3½ -inch configuration to conform around any support collars and bolts.
3. Apply adhesive over the butyl tape.
4. Set the collar around the support and tighten as required.
5. Fill the pan around the collar to half full with adhesive.
6. Place the support pipe into the collar and tighten as required.
7. Set the drainage field (if required) around the support.
8. Apply sealant at the juncture of the support and concrete.