Pier and Beam Repair San Antonio
A common foundation type built on expansive soils prior to the 1960’s was the pier and beam design. The basic principle is to construct the piers such that they are below the depth of seasonal moisture changes. The piers can be belled at the bottom to increase their uplift resistance.
As an alternative, it has been stated that the depth of the piles or piers should be 1.5 times the depth where the selling pressure is equal to the overburden pressure. Grade beams and the structural floor systems that are free of the ground are supported by the piers.
Most structures built today are built with various designs using post-tensioned slab on grade or steel reinforced mat, particularly in areas of expansive soils such as found in Texas, Oklahoma and Kansas and parts of Missouri. Common problems of expansive soils damage include insufficient pier length, excessive pier diameter, absent or inadequate pier reinforcement, excess concrete on the top of the piers, and an absence or inadequate air void space below the grade beams.
Causes of Sagging Floors Over Pier and Beam Foundations
Sagging floors are not only a nuisance but will leave you thinking “…how much longer will the floor be able to support the weight of my house?”
- Columns are spaced too far apart. When a crawl space is built, block or brick columns are located throughout the crawl space to support the weight of the house above. If the columns are space too far apart, the beam or girder can become overloaded and sag. When the beams sag, so does your floor above it.
- Floor joists and girders weakened due to moisture and wood rot. When crawl spaces are sealed from the ground, excess moisture and humidity can be a huge problem. This added moisture can then cause the joists to become moldy, begin to rot and weaken. The weakened joists and girders are unable to support the weight above and the floors become bouncy, soft and begin to sag.
- Columns settle due to weak soil. Weak, expansive soils can cause existing columns in the crawl space to sink or settle, often creating a gap between the top of the column and the bottom of the girder it was supporting. This causes the floor to sag.
Correction of pier and beam foundations is a challenge to the foundation repair company because each case must be evaluated individually and a case specific solution must be developed. Most of the problems with pier and beam construction can be addressed with remedial techniques.
One possible common solution is the deepening or additional installation of footings. This technique starts with the excavation of slots in order to install hydraulic jacks. After the hydraulic jacks have been installed, the entire footing is exposed. Steel reinforcement is then tied to the existing foundation by dowels. The final step is to fill the excavation with concrete. The jacks are left in place during the placement of the concrete.
Concrete columns can be added by installing additional footings throughout the crawl space. After the footings cure, concrete blocks are stacked on top and shims are placed between the uppermost concrete block and the girder.
In some cases, additional shimming can be added to existing columns by using a temporary jack to lift the girder to make room for the shims; the jack is then removed.
A recent and sturdier technique uses a heavy-duty steel support jack system. A 2 foot cube of soil is excavated at each location and filled with concrete or engineered fill. A high strength, galvanized steel column is cut to the appropriate height and connected to the girder. The girder and floor joists are stabilized with the jack system and by lifting the floors and walls back to level. This is a preferred technique because is addresses the underlying expansive soil problem.
Crawl space encapsulation is a critical component of a successful pier and beam renovation project.
The professionals at Foundation Repair Pros have years of experience in dealing with pier and beam foundation issues. Give them a call today!