post tension cables
Post-tensioned concrete incorporates 1/2 inch steel cables to provide internal stress as a means of transferring or counteracting eternal loads a concrete slab is designed to support. Slab design is based on a soil analysis accomplished before any home construction should begin. The foundation plan and beam detail sheet provided by the slab engineer outlines the method for constructing a foundation capable of withstanding the forces and loads expected for residential housing. The slab engineering firm performs a cable inspection after the cables have been stressed, then issues an inspection compliance letter and FHA stress certificate. You should retain these documents for your record.
CHECKLIST FOR POST TENSION CABLES
Checklist after Slab-Placement
- Call the post-tension company on the day of slab placement to coordinate cable-stressing dates.
- Track the days since slab placement and ensure the cables and stressed within 7-10 days. The live ends will not be cut until cable elongation and condition have been inspected and approved by the slab engineering company
Post Tensioning Process
- When possible observe cable stressing while the post-tension contractor is on site. Inspection and approval is essential!
- Visually inspect each anchor to determine if the wedges are seated evenly
- Check the elongation at each cable. Before stressing, the post-tension cable company should paint the exposed portion of the live end (where it protrudes from the anchor). After stressing, this identifying mark is the basis for measuring the amount of cable elongation. Approximate elongation should be 1 inch for every 12 feet of cable length between anchors.
- Contact the slab engineering firm to follow-up on the scheduling of a cable inspection. Occasionally the post-tension contractor forgets to coordinate.
After Inspection
- Check all live and dead end locations to ensure the contractor has cut all cables, neatly grouted each hole and cut all exposed nails protruding from the slab
- Ensure all debris is removed from around the slab. Make sure all trash is in the trash barrel and construction debris is piled at the front of the jobsite.
