What is Underpinning?

Underpinning refers to reinforcing the foundation of a structure, such as a house or building, by extending the existing foundation to distribute weight load across a greater area evenly. To begin this major repair project, soil directly beneath the foundation is excavated in stages to minimize the risk of undermining the structure. A foundation repair professional calculates the depth of excavation based on soil type and layer strength before replacing each layer with an underpinning material. This process continues until the complete structural base is reinforced, creating a stronger foundation for the building or structure.

Benefits of Underpinning

Basement underpinning is necessary when the existing foundation has shifted so substantially that it can no longer safely support the house. In some cases, the original support was inadequate for the area’s climate, soil condition or type. Also, it could be due to all or part of the original foundation resting on marginal land with a bearing capacity insufficient to hold up the home. In other cases, structural integrity deficiencies are due to inexperienced contractors whose poor work you’re still paying for.

Underpinning your foundation opens the hidden mechanics of the home and makes them accessible for inspection, correction and improvement
As underpinning is usually undertaken in older homes, there is old plumbing, electrical and insulation systems that can be replaced or upgraded with modern technologies. All these can be brought up to Building Code and to contemporary standards.
Changes will have to be made to the waterproofing systems along with the underpinning so the life of the useable, dry space is prolonged.
Long-term savings in energy costs
Improved foundation strength
Increases home value

Signs You May Need Underpinning

Floor & Wall Cracks

Cracks aren’t always scary. Sometimes they are superficial, such as minor or hairline cracks in plaster, cornices and skirting boards. Bigger cracks are another story and usually point to bigger underlying problems, such as uneven weight distribution due to weak foundations.

Cracks to look for could be interior (plaster, wall and floor tiles) or exterior (brickwork, render, concrete slab).

Ideally try to observe the cracks over a period of weeks or months to determine if the cracks you’ve noticed get bigger, wider or longer - or if new cracks appear. If they remain unchanged over a long period, the subsidence has likely run its course and the house has settled.

Unlevel Floors

Something that isn’t always as obvious as cracks is unlevel floors. When you are able to identify them however, a lean to one or more sides of your home is a strong sign that there are significant foundation issues at play.

In serious cases we’ve seen, you can stand at one end of a hallway and see the fall of the house as you look down the hall. Other times, unlevel floors will contribute to misaligned doors.

Generally you can use a spirit level to get some idea of how unlevel a room is. Or place a ball in a room and see if it remains still or if it rolls in a particular direction. But to understand how significant this is usually will require a professional.

Another thing to look for are irregular trenches forming around the edge of the building or slab, in the top layers of the soil. This is another sign of subsidence.

Unaligned Doors & Windows

Doors and windows can be good indicators of foundation problems.

Gaps appearing and getting wider around your windows and doors. Finding it hard to close (or reopen) your doors or windows, or not being able to lock them.

In more advanced cases, there are more visible leans to door, and door or window frames may begin pulling away from their surrounding walls.