Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
(OP)
Typical practice in my area is to utilize #4 rebar stakes to chair the post-tensioned tendon in the bottom of the grade beams (3" clr cover). The PTI Construction and Maintenance Manual for Post-Tensioned Slab-on-Ground Foundations (PTI DC 10.2-06) appears to approve the practice in Fig 5.13 (see attached) with the notes "steel or plastic stake or other method of positioning tendons in rib".
My concerns include:
My concerns include:
- Penetrations in the vapor retarder which greatly increase its permeance.
- Moisture in the bottom of the slab corroding a steel stake and causing damage in the bottom of the grade beam.






RE: Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
Thaidavid
RE: Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
The 'infamous' Dr. Joe Lstiburek and Fick's Law have something to say on this subject, here: Link
RE: Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
http://www.stegoindustries.com/hubfs/Technical_Art...
https://www.wrmeadows.com/data/Under%20Slab%20Vapo...
RE: Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
And Brewer's results from 1997 testing (in the Stego link too) had a slab with w/c ratio of 0.7. That is a butt load of water.
RE: Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
I always take Lstiburek's stuff with a grain of salt. Building science guys always seem to change their tune about things later in life. Of course, it is already too late for the folks who took their earlier advice.
RE: Steel Stakes Puncturing Vapor Retarder in Slab-on-Grade
Dave
Thaidavid