Commercial Building Floor Lifting

High Density Polyurethane Foam Jacking for Floor Lifting in Commercial Building in Virginia Beach, VA.

Structural Engineer:
Fadi Debbas, PE, ABC Consulting, Inc., Norfolk, VA, www.abcnorfolk.com

Challenge:

The floor inside of a single commercial building on the Virginia Beach oceanfront containing a restaurant and t-shirt shop settled up to 11.7 inches.  The floor inside of the restaurant had settled up to 4 inches, but had been repoured previously with overlap onto the top of the t-shirt shop’s floor slab, which was settled more than 7 additional inches.  In addition to floor settlement, there were up to 3 inch deep voids under the slab.  Backfill material could not tolerate additional burden weight from traditional materials which were used to build up subgrade as part of previous replacement repairs, as evidenced by continued resettlement.

The amount of settlement was enough that salt deposits had developed on carpeting as a result of sea water inundation of the void under the slab during high tide coinciding with heavy precipitation events.

Limits: 

Work area shared a common, metal framed wall with a busy, high-profile restaurant which could not be disturbed.  When the building was constructed, it was built on top of an abandoned basement from a previous structure on site, which had been backfilled with debris and beach sand, none of which appeared to have been properly compacted.  Two stretches of sanitary sewer lines under the floors had developed bellies up to 15 inches deep, and there were leaks at multiple locations due to subsoil and floor settlement.

Solution:

Lightweight, high density polyurethane grouting to fill voids under the floor and raise floor.  Due to extensive cracking of floor, slab was initially undersealed with slow reacting foam to lock all pieces together.  After the slab was undersealed, crew switched to a faster-reacting, aggressive expansion lifting foam to minimize loss of material and lifting ability adjacent to multiple floor cuts.

Result:

Two CJGeo polyurethane grouting crews successfully completed the lifting work over a period of two days.  During floor lifting and stabilization work, preparation for single-component soil stabilizer chemical grout was performed. Concrete Jack successfully lifted the floor back within tolerance of original grade, with the least amount of burden weight placed on the underlying fill material.  Due the rapid cure time of polyurethane, plumbers were able to immediately cut access to the plumbing repair areas.  After areas of floor were removed, the plumber was able to cut through polyurethane under the floor with a reciprocating saw, greatly increasing the ease of repair compared to a Portland-based grout material.

High density polyurethane provided 100% waterproof undersealing of the floor to help prevent future water inundation.