Bowing Stone Foundation, Bow, NH

Tuesday, July 26th, 2022 by Niles Erickson

Challenge

This homeowner in Bow, New Hampshire reached out to Erickson Foundation Solutions with concerns regarding his bowing foundation wall. The home is a 200 year old structure with a mostly granite stone foundation, with some brick sections as well. At the front of the home, there was a set of large granite steps. Granite of course is heavy, and over time these heavy steps pushed down on the soil beneath them. This compacted soil in turn kept pushing against the home's foundation wall, eventually causing it to bow inward.

As the wall bowed in more and more over the years, the homeowner became concerned that eventually the wall would be completely beyond the sill plate and no longer properly holding the weight of the home above. This was lead to further damage and perhaps even total collapse of the foundation or even the this side of the house.

Given the age of the structure, and the unique arrangement of the granite foundation walls, the homeowner was seeking to work with a contractor with the knowledge to handle such a project. Erickson Foundation Solutions has repaired hundreds of similar foundations and was on hand to design the ideal, permanent solution required for this problem. The homeowner also knew that if he did nothing to fix the bowing wall now, the problem would get worse. They also wanted a solution that would not disrupt or displace any of the existing foundation so as not to hurt the integrity of the old structure.

The following challenges needed to be addressed;

Stabilize a section of bowing, granite foundation wall.
Due to the age of the home, removal or replacement of the existing walls granite material was not advisable.
Design a permanent solution and warranty the work.
Make the repairs without disturbing the exterior granite steps or displacing any soil.

Solution

When it comes to fieldstone foundation wall repair, removing sections or even repairing sections of the wall can be tricky. The material is unpredictable and susceptible to collapse if it is moved too much or in the wrong way. Due to this concern, Erickson Foundation Solutions developed a wall repair system in conjunction with other Supportworks network foundation repair specialists, called Auxiliary Wall Support. Essentially, instead of removing and replacing sections of the wall in question, an additional wall system is added to abut the existing wall, keeping it from bowing, leaning, or crumbling any further. The auxiliary wall was the ideal solution for this home in Bow, New Hampshire.

The auxiliary wall for this project was designed to be 16' in length. It would be an 8" (inch) thick, 4" (foot) high, poured concrete wall, reinforced with vertical steel brackets and horizontally running steel rebar.

The first step involved installation of 5 PowerBrace Wall supports along the 16' span of the bowing foundation wall. These PowerBrace's were anchored to the concrete floor below and also to the solid floor joist system above. While PowerBrace's themselves are generally enough to stabilize a poured, concrete foundation wall from bowing or movement, when it comes to fieldstone foundation walls more is needed. The stones comprising the wall require more material to ensure they are each individually stabilized. In addition to these vertical brackets being anchored to the floor and ceiling in the basement, they were also connected with horizontally placed steel rebar rods.

Once all of the steel was in place, the production team then installed forms for containing the poured concrete, similar to how forms are used for pouring new concrete foundations. To make the process easier, the concrete is delivered by truck, poured into a pumping system, and pumped into the forms with large hose tubes. Once the forms are filled, the wet concrete is allowed to cure. It fully encompasses the steel anchors and rebar, tying the wall system together for complete stabilization. When ready, the forms are removed and the concrete, auxiliary wall is complete. The system is clean and efficient, and much more cost effective than fully replacing the foundation wall for the homeowner. The final step is installation of a couple SmartJack columns to assist with supporting the floor joist system above.

Due to some moisture concerns, the homeowner also decided to install a SaniDry Dehumidifier system.