Thread: 6 mil poly under exterior grade beam?

I was asked to looking at a foundation pior to pouring within the next several days. My question...Shouldn't 6 mil. poly be located under the exterior grade beam and up to the exterior form boards?

Similar Threads:

• Exterior walkpaths - - Question for Texas boys and girls!
• Exterior Installation of Gas Flex Line
• Exterior JB
• Staining on exterior wall near A/C
• Brick Veneer Exterior Wall 90 deg inside joint

Why would you want to inspall poly under a footing? Size and proper depth are your critical points.

Originally Posted by Larry Zatopek

I was asked to looking at a foundation pior to pouring within the next several days. My question...Shouldn't 6 mil. poly be located under the exterior grade beam and up to the exterior form boards?

It is a good practice to run poly under (and at least partly up the exterior) of the grade beam in colder climates where there can be a dew point (condensation/mold) issue.

Other than any local AHJ requirements, I don't know of any code requirements.

Take a look at this document - Info-513: Slab Edge Insulation — Building Science Information

The required locations of the poly should be depicted in the engineered drawing. Some engineers require it to come up to the form boards, others just under the beams.

Darrel Hood
DILIGENT PROPERTY SERVICES

When inspecting this, remember if the 6 mil poly goes under the beams, you are defeating the concrete encased grounding electrodes required in 2008 NEC. Section 250.52 (A)(3) requires direct contact with the earth.

Originally Posted by Larry Zatopek

I was asked to looking at a foundation pior to pouring within the next several days. My question...Shouldn't 6 mil. poly be located under the exterior grade beam and up to the exterior form boards?

No, you do not want it under the footers. Under the slab, if it is a slab on grade.

Many builders and architects don't know or ignore the correct procedure when installing a vapor barrier under a slab on grade. 95% of the slabs I see do not reach the wall footings and the moisture will find it's way in.