Stone Foundation Raising and Support
THE CAUSES FOR STONE FOUNDATION SETTLEMENT AND HOW TO RAISE AND STABILIZE A STONE FOUNDATION. HERE'S WHAT YOU NEED TO KNOW...
- STONE FOUNDATION REPAIRS
- STABILIZING STONE FOUNDATION
- RAISING STONE FOUNDATION
- FOUNDATION SETTLEMENT PROBLEMS
- STONE FOUNDATION SINKING
The Problem
Stone foundations are often found on older, historic homes and buildings, posing a difficult problem when settlement has occurred and stabilization or raising the structure is desired. Typically, stones were cut and placed to fit tightly together, sometimes with mortar and sometimes without. If mortar was used, it is likely to be aged to the point where it no longer provides a uniform load transfer throughout the footer stones and the foundation becomes fragile and sensitive to movement. It is the potentially loose condition of the stones that makes compaction grouting uniquely suited to stabilizing or raising a stone foundation.
Compaction Grouting was developed as a corrective method to address the causes for foundation settlement versus treating the symptoms.
What is Compaction Grouting?
Compaction grouting is the injection of a low mobility, stiff, grout into weak or unstable soils beneath a foundation or structure in order to fill voids and densify the supporting soil beneath. The densification of soil increases its bearing capacity and hence, its ability to b. Injections are done to depths where stable soil is found at locations far beneath the foundation or structure. Injecting a “bulb” of stiff grout into a soil displaces, densifies, and pushes it upward in a controlled manner. High pumping pressures of 600 p.s.i. are used and carefully regulated to first stabilize, and then if desired, raise the structure.
How it works...
Steel injection pipes are inserted to the bottom of the zone to be stabilized, at times far beneath the foundation. Soil borings are typically required to identify the problematic soil zones to be treated. Pipes are either drilled or driven into place and then retracted a few inches to open the end of the injection pipes.
A low volume, high pressure pump is used to inject the stiff grout. As the grout expands into a homogeneous bulb, radial forces are exerted uniformally into the surrounding soil. This action of displacing of the soil fills voids, drives out perched water and densifies or compacts the supporting soil. Pumping is done slowly to avoid fracturing the soil, and to allow excess water to dissipate. If raising the structure is desired, low volume pumping continues until the soil is beyond the point of compaction and begins to heave. Since the grout bulb was placed beneath the foundation footing and some distance away, its effect on the foundation is indirect. The displaced, compacted soil is in direct contact with the foundation and uniformally pushes the foundation upward in a controlled and exacting manner. For either stabilization or raising, this is done with minimal disruption to the fragile condition of the stones. The compacted soils pressing against the underside of the stone footing is broad and distributed and point loading is avoided.
Why it's important...
Foundations are designed to be uniformally supported by soil. Compaction grouting maintains this contact between foundation and soil as intended with little change to the designed function of the structure. Other, more notable piering and piling systems for foundation raising are not designed or for stone foundation raising or support. Many times owners of these turn of the century buildings desire foundation stabilization versus raising for a number of reasons. Often these exquisite structures have undergone extensive and expensive remodeling or have been upgraded and owners wish to avoid disrupting a present elevation and avoid cracking.
In these preservation-focused cases, compaction grouting can be a method that provides substantial cost savings with minimal disruption.
Compaction Grouting Advantages
- Addresses the causes of your settlement problems, not just the symptoms
- No excavation needed with compaction grouting
- Minimal disruption and project duration
- Not necessary to remove portions of the foundation, footings, driveway, sidewalks, patios, decks, landscaping, or floor slabs
- Compactions grouting stabilizes and supports foundation uniformly by maintaining or reestablishing complete contact between the foundation and the supporting soils beneath to allow the foundation to function as it was designed
- Grouting equipment is left curbside, not on your lawn or driveway, eliminating the need for messy cleanups
- Stone Foundation repairs are undetectable upon completion
- Low cost – less expensive than other methods