The Basics of Stabilizing a Settled Building by Underpinning

 

The foundation of a house can move over time. If the movement exceeds the footing’s limits, the footings will experience excessive stress such that they will rotate, bend, or crack.

The stress is also experienced by the wall or concrete slab above. Consequently, the supported structure can experience masonry cracks.

In severe situations, the integrity of the structure may be compromised. The nature and extent of the masonry cracks may indicate what caused the stress load.

 

Causes of Structural Problems

Concrete cracks or hairline plasterwork are issues resulting from shrinkage. Thus, treat them as cosmetic issues.

However, long stepped or zigzag concrete and masonry cracks should be a major concern that needs immediate investigation and fixing before they develop into a bigger problem. They’re usually caused by:

• Environmental Changes
• Poor initial construction
• An aged building
• Additions and alterations to a building

1. Environmental Changes

Natural or man made environmental changes may have an impact on the performance of a foundation. A building that was originally built on piles such as concrete piles or screw piles may not suffer damage.

However, a slab set on a ground-based footing system may suffer damage due to environmental changes such as:

• Removal of huge nearby trees
• Changes to the level of the water table
• Changes in the soil moisture levels
• Adjacent excavations (either new or old)
• Nearness to a water borehole or ongoing dewatering activities

Problems related to foundation movement or cracking of the cellars, basement, swimming pool, or walls might not be clearly visible until the soil beneath the footings consolidate towards a nearby filled excavation that’s yet to be compacted.

 

2. Poor Initial Construction

If your home was designed by a licensed and experienced engineer as per the local building standards, then it’s unlikely that the construction method used is the cause of the appearing cracks.

However, if building standards weren’t followed, then it’s likely that the cracks are appearing as a result of poor materials and/or poor workmanship.

Also, local construction codes advise that the life of a residential property is 50 years at most.

Experienced and reputable builders acknowledge that shortcuts when constructing the foundation may lead to costly remedial work during their guarantee period. Thus, their reputation may suffer. As a result, they take their work seriously.

Unless the contract of a builder allows for any latent conditions on the ground, they’ll incur more construction costs.

Thus, an inexperienced or unlicensed contractor may take shortcuts with the aim of offsetting such costs. Consequently, the foundation may experience movement and settlement problems.

 

3. An Aged Building

The technology of building foundations has advanced quite significantly. Older houses built on sandy sites before the 1950s were built on basic foundations comprising of flat bricks laid in a row and walls built on top of the bricks.

Another technique used back then was laying huge limestone blocks and building brick walls above. The brick walls featured double cavity bricks.

These design techniques created rigid structures as long as there would be no movement of the underlying soil.

While there are many houses older than 100 years that are still in good condition, their foundations will eventually move, leading to the development of large cracks in the walls.

Although you can fill and close the holes with some products, a more permanent solution to fix the problem from its root would be needed.

Older buildings often experience several problems. One of these problems is changes in environmental conditions. These changes include changing soil moisture level, nearby excavation, or tree removal.

Luckily enough, a settled or weakened foundation can be fixed by hiring a Melbourne underpinning company in Melbourne. It involves the use of concrete and beams or strip footings.

There are several underpinning configurations used depending on the ground conditions and the design of the building.

 

4. Additions and alterations to a building

If you’re adding an extension to an existing building, you must consider the impact of the extension on the existing foundation.

This is because the extension may compromise the foundation in case it’s unable to handle the extra load. Thus, the foundation should be upgraded and strengthened to support an extra level on top.

 

Fixing Foundation Movement Problems

There are several signs of possible foundation movement. For instance, if the windows or doors are sticking when opening or closing them, you should worry about the condition of the foundation. Another major sign is crazed cracks near a window or door.

If you suspect that the foundation is moving, act soonest possible to avoid a bigger disaster. Ignoring major cracks and failing to investigate the cause can result in costlier repairs.

Monitoring the movement early enough will assist in higher chances of successfully fixing the problem. By monitoring the situation, an expert will be able to tell the cause of the issue and recommend possible solutions.

 

The steps below assist in accurate foundation movement monitoring:

Step #1

Get telltales and place them along the crack. Each telltale should be numbered. The telltales can be plastic rulers or tapes.

 

Step #2

Take a marker pen and mark the position at which both edges of a crack are situated on every telltale.

 

Step #3

Record the distance from one marking to another on the telltales. Also, take note of the date you have taken the measurements.

 

Step #4

Measure the distances weekly to monitor whether there’s further movement.

 

Step #5

Take note of any soil saturation or rain.

The telltales will tell whether there’s a continuous movement of the foundation. If you aren’t confident enough to do the monitoring yourself, hire a builder to do the work for you.

If you can do it yourself, then you’ll save more money during the entire process. Ensure you take accurate measurements and record them clearly.

A structural engineer wouldn’t rely on unclear and inaccurate records. If you take inaccurate records, the structural engineer will have to repeat the monitoring process.

If structural movement is noted, it’s advisable to have the problem fixed soonest possible before it worsens and becomes costlier to repair.

Upon confirming structural movement, a structural engineer should assess the condition of the foundation. Only hire a qualified and licensed structural engineer for the job.

Once the engineer inspects the foundation, they’ll give you a detailed report of the problem. They’ll also recommend the best solution to fix the problem.

Also, notify the engineer about relevant historical incidents concerning the house and its surroundings. Thereafter, you’ll present the engineer’s report to a builder.

There are several methods used to stabilize a foundation. They include:

• Traditional underpinning
• Screw pile underpins
• Soil injection systems
• Concrete piles
• Micro-fine cement grout injection

The best method to use in fixing a foundation depends on the site access, your budget, and the nature and extent of the issue.

It’s also possible to jack the foundation and the walls back to their original position. However, jacking up the foundation can be quite expensive.

In some situations, jacking can be used to relocate a wall back into position and closing the gaps, though it’s not always guaranteed to work. Also, filling the cracks will be required to seal the cracks after jacking the structure.

Jacking with a hydraulic system is usually done after installing piles beneath the footings. Also, any jacking gap is filled with concrete to get rid of all gaps and seal the jack in place.

 

The Cost of Repairing Foundation Movement

An engineer’s report may cost you around $500-$3,000. The cost will depend on the complexity and extent of the issue, the geotechnical tests required, and the level of inspection required.

Typical reports for most issues cost around $1,200-$1,500. The report will include the best solutions to fix the foundation movement. A reputable engineer will recommend the most cost-effective fixes for your own benefit.

The recommended solution will be based on several factors including disruptions to the most used areas, site access, and ground conditions.

Problems that require jacking the building contribute significantly to the overall cost. Minor works may only cost around $1,500 while work on an entire house can cost at least $50,000.

It’s advisable to avoid leaving foundation problems unattended. Delays may result in further problems and costlier repairs.

 

Advisable Action Plan

1. Talk with your insurance provider and let them know that you’ve noticed structural problems in your house.
2. Start monitoring any major cracks and record them.

• Talk to a structural engineer and arrange for an inspection of your house or provide them with the details of your insurance company.

 

Read: Differences between Resin Injection and Concrete Underpinning