What Exactly is Underpinning & When Do You Need it?

A building foundation that has already been reinforced is known as underpinning. Underpinning is used when an existing building foundation cannot support the weight of the home. Usually, this is the result if the soil has changed in structure due to changes to soil types or other external influences. More information is available read this!

What constitutes underpinning?

Underpinning is a process that supports or strengthens the foundation of existing structures, such as a home or building. To achieve this, you can reinforce the foundation by adding an expanding filler to the soil, or extend the foundation by increasing the surface area.

When do you need underpinning for your home?

The majority of homeowners require underpinning when the original house foundation is insufficient to support it. This usually occurs as a consequence of:

The soil under the foundations has changed, in one way or another. through subsidence, expansion/contraction due to moisture, large trees nearby, damaged plumbing left unrepaired.

It is possible that soil conditions were not fully considered when designing the foundation.

There are also less frequent situations where underpinning might be needed for:

This could be because the use of the structure changed, e.g. A major renovation has taken place

Construction of new buildings nearby will result in excavations to support foundations.

For example, to increase the ability of an existing foundation. To allow the addition of another story.

Natural disasters such earthquakes. floods. or droughts. that caused the structures to be unstable.

To help you understand when and if foundation underpinning might be necessary, take a close look at key components that influence a base.

Different soil types are classified according to their classification and type.

This is because the type of soil plays an important role in foundation stability. Certain soil types tend to undergo more structurally significant changes. The soil conditions can change significantly during long periods of dry or wet weather. The soils that are reactive in nature.

This will affect the amount of damage done to the house and determine which method is best to stabilise the building.

Why do construction foundations fail?

Many reasons can cause the foundations in a house to collapse.

Reactive Soils

The main problem usually involves soils which are very reactive. These movements can involve shrinkage (which results in settlement) or growth (which produces heaving). When conditions are consistently dry, soils lose moisture over time and begin to shrink. When soil moisture levels rise, for example during periods of prolonged wet weather conditions, the soil can grow by as much as several hundred percent.

In addition to shrinkage, soil expansion can also compromise foundation integrity, leading to visible cracks on walls, foundations, or heaving.

Compacted Fill that Is Not Good Enough

The material that was used to fill a space may not be sufficiently compacted in order to support the load of a structure. These situations are prone to foundation problems. It can result from a poorly compacted foundation, multiple filling materials used, or both.

Site Erosion

Eventually, erosion can compromise the structural integrity of foundations. Erosion is caused by a wide range of factors, including burst or uncontrolled pipes or water flows, improper drainage, and the like.

Inslope Failure

When a slope fails, the soil moves downhill. There are two types of failure: slow or abrupt. In the case of a slope that is in danger due to “creep”, underpinning may be necessary to fix the problem. The site is specific, and an expert must assess the situation.

Foundation Design

A foundation’s design could have also been insufficient. If the soil properties weren’t properly understood at the time of foundation design, then the foundation may be inadequate. Due to modern construction codes, it is not as common.

Do I need underpinning?

Some signs are important when assessing your home yourself. While reading the following list, you should understand that subsidence occurs in varying degrees on many properties. The only time that underpinnings are required is when subsidence is occurring. After the subsidence first occurs, it is not uncommon for the structure to reach a point of equilibrium. Ask a professional for help if you have any doubts. Our Home Checkup Service is complimentary.

Cracks appearing in floor or wall surfaces

Not all cracks are scary. Sometimes cracks appear to be minor and hairline, for example in plasters, cornices or skirtings. These larger cracks usually signal a deeper problem.

There are cracks that can appear on both the exterior and interior surfaces (brickwork or render) of your home.

Ideal is to keep an eye on the cracks and observe them over weeks or month to find out if there are any changes. When they stay the same, it is likely that the house’s settlement has been completed.

Levelling the floor

Unlevel floors may not be as apparent as cracks. Uneven floors are an important sign that foundation problems are present.

When the situation is serious, we’ve even seen people standing on the one side of a long hallway looking down and seeing the whole house collapse. Other times unlevel floors may contribute to doors that are misaligned. In general, you can make use of a spirit gauge to estimate how level a given room is. Try placing a ball and watching if the ball rolls or stays in place. This is often difficult to grasp without the help of a specialist.

Also, irregular trenches can form around the outside of the building. These are usually in the surface soil. The soil may also show signs of subsidence.

The doors and windows are not aligned

Problems with foundations can be indicated by problems around your windows and doors. There are gaps that appear and get wider around the windows and your doors. You are unable to lock or close your door or window.

As the condition progresses, it becomes more obvious that doors and window frames are beginning to move away from the walls.

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