Underpinning a Building

Underpinning a Building

Underpinning is a procedure used to stabilize a building that has a failing foundation. The most common reason for a failing building foundation is deterioration of the supporting wooden structure. The wood may begin to fail when it is exposed to moisture over time, or termites damage could also be the reason. In any case, the foundation must be repaired or the building will eventually collapse.

There are other possible reasons that a building needs underpinning, some of the reasons being that an additional story is being added to the existing structure, the building has moved due to a natural disaster or the supporting foundation soil has changed.

The first step required in the underpinning process is providing a permanent stable surface on which to place screw piles. The underpinning supports should only be placed under load bearing walls, beginning at the four corners of the structure and advancing inward. The recommended size of the concrete support is 3 feet long by 2 feet wide at a depth of at least 2 feet. The concrete must set up for a minimum of two days to ensure it has cured properly and is strong enough to support screw piles and the weight it supports.

Holes for house foundations
Holes for underpinning

Underpinning brackets must be used to ensure the screw pile remains securely in place as it is used to raise the foundation to its former position. In certain cases screw caps are used to connect the pilings to a reinforced concrete beam.

Any time the foundation of a building begins to fail, it is necessary to consult with a structural engineer to determine which method of underpinning is recommended. If proper corrective measures are taken before too much damage has occurred, a building can be stabilised and remain usable for many years.

Concrete pour for footings
Concrete vibrated for footing

Restumping A House And What It Involves.

One of the processes of building a foundation involves placing concrete or wooden posts in the soil beneath the foundation. Holes are dug and these posts are placed below the material that is used for the foundation.

With time the soil beneath the foundation settles. When this happens, the posts which are also referred to as stumps, may move. This causes damage to the foundation. It develops cracks and the entire house is at risk of being unstable. Wooden stumps can also rot after being in the soil for a while thus resulting to the need for restumping.

Older Red gum stumps

So how is the process done? For wooden posts or stumps, a hole is dug next to the post. This hole is tiny about six inches wide. This will provide room for the contractors to check whether the post has rotted. If this is the case, the foundation is supported by use of machines. The posts are then repaired or replaced if the damage is too much.To know whether the posts have rotted away, the contractor pierces the wood to see if it will give in. If it does, it is an indication that it needs replacement.

For concrete stumps, the signs of damage are harder to spot. If you are careful though, you will see them in the foundation or the windows and door frames. If there is damage to the concrete posts, it is repaired by adding a new layer of concrete on the post to make it stronger.

Concrete Stump attached to bearer
Concrete Stump attached to bearer.

Naturally, the stumps made from concrete last longer because wood rots quickly especially in wet soils. It is therefore advisable to choose concrete stumps for your foundation. Furthermore, after the restumping, ensure the walls or the foundation itself is not damaged. You can have the contractors check on this.

All You Need To Know About Reblocking

Are you planning to take on a home improvement project? Before you begin, it’s wise to check the integrity of your home’s foundation first. A solid design and laser-perfect levels are required to ensure the overall durability of a home. Over time, however, the timber stumps that support your home may suffer from wear and tear. This causes the piers to sink. Timber stumps that have rotten can make the problem even worse. In such a case, a reblocking project is in order to strengthen the foundation of your home.

What Is Reblocking?

Reblocking is the process of replacing timber stumps with stronger and more durable concrete or steel stumps. This is commonly done on weatherboard homes and brick homes. These types of houses usually have timber stumps underneath. As timber stumps rot, their tips get pointed, causing the weight of the house to bear down on the stumps and the levels to be uneven.

Repair and Levelling
Sub floor levelling

When To Reblock?

There are telltale signs that indicate you need to reblock the foundation of your home. If you notice any of the following, it’s time to call in a reblocking specialist:

-Slanting floors

-Difficulty opening or closing windows and/or doors

-Cracking tile floors

-Moisture in foundation

How Is It Done?

The process begins with a visual inspection. A reblocking expert scratches away the soil from the stump’s base to evaluate its condition. This involves the removal of plinth boards. Jacks are placed around the house to provide support during the removal process.

Reblocking repair
Weather Board home getting new stumps

Holes are dug to reach the plate. After this, the actual removal of timber stumps commences. New stumps are hung over the holes, leaving ample space for concrete. Special equipment is used to ensure that the house has a perfectly straight level. The concrete is then poured into the holes. The jacks are removed 24 to 48 hours to allow the concrete to set.

How To Tell When You Need To Repair Your Home’s Foundation

If you have a home, then you need to know what to watch out for when it comes to its foundation. There are repairs that can be done no matter what condition the foundation is in, but the earlier you take care of problems the easier they will be to take care of.

Are your windows on hard to open now or have they been sticking as of late? Any sudden change with your windows could be due to a foundation issue. You should also look around your home for cracks over your doorways, where walls are meeting your ceiling, and on walls. Another place that cracks can appear would be on your floor.

Cracks in plaster
Cracks in plaster walls.

Puddles can be a sign of moisture getting into the foundation if you see them in crawl spaces. If your foundation’s perimeter is having drainage issues, you may have a little bit of a problem. This is one reason why you need to keep gutters clean, because they can keep water away from the foundation.

Horizontal cracks are something you have to watch out for carefully. Soil can get saturated in water, and then may expand if it freezes. If that happens and it pushes on the foundation too hard it will cause the foundation to break. This may mean it’s too late for your foundation because severe damage like this is not going to be easy to fix. However, there are experts that can completely replace what you have so you can save your home.

Do not delay when you notice any of the issues that were outlined here. Foundations are not going to be perfect and the sooner you notice issues the better. Check over your home on a regular basis and the early warning signs should be easy to detect.

Cracks in plaster above door
Cracks in plaster above doorway

Effects Of Leaving Failing House Foundations Untreated.

House foundations shift due to a number of reasons. Most of the time it has to do with the soil that is beneath the foundation. When this happens, the house starts to show signs of a failing foundation.

This is a problem that should not be ignored. When soil settles beneath the house, it causes the foundation to crack. These cracks can often lead to the collapse of the house. Leaving the foundation un repaired could cause damage to the entire house, not to mention pose a risk to your life.

A weak foundation should be repaired immediately to ensure the walls do not cave in. This is risky because the entire house could collapse when a person or pet is inside. Additionally, all the property will get damaged and this will be costly.

Apart from that, when a failing foundation is not repaired, it gets more damaged. This means that you will have to spend more money eventually to fix the entire foundation. The situation only gets worse with time. It is best to save funds by fixing the cracks earlier on.

Crack in plaster
Crack sin plaster

Even when the foundation is getting damaged at a slower rate, do not be fooled into thinking that it will not affect you. You may decide to sell the house a few years down the line. A damaged foundation will lower the cost of your home noticeably. The value of the house drops due to the repairs that will need to be made.

Another terrible effect of leaving a failing foundation un repaired is that if there are cracks, you will be prone to water damage during the rainy season. The cracks will let in water and your belonging will be damaged.

If you have a failing foundation, ensure that you call us a soon as possible.

Cracks in bricks foundation
Cracks in bricks

How Long Does Underpinning House Foundations Take?

Underpinning a house to strengthen its foundations becomes necessary in the event of subsidence – when unstable soil causes the foundations to sink – or if you want to add extra floors.

Either way, underpinning technologies have advanced rapidly in recent years, and several different methods are now available.

Because of the complexities of the job, it’s difficult to predict exactly how long an underpinning project will take, but on average it works out at around four to six weeks.

However, some underpinning or restumping jobs may take longer, especially if unforeseen snags arise – a particular problem in older houses.

For instance:

  • Utility lines may need to be relocated.
  • HVAC (heating, ventilation and air conditioning) systems may have to be modified.
  • Basement stairs could need extending or rebuilding.

The Underpinning Process

Underpinning begins with digging out the ground around the foundations. This is followed by the actual underpinning process. Three techniques popular among Melbourne underpinning contractors are:

  • Concrete underpinning.
  • Placing reinforcing beams.
  • Resin injection.

Concrete Underpinning

Concrete underpinning is often used for smaller jobs. It involves pouring concrete into excavated cavities. As the concrete sets, it forms a new foundation underneath the existing one. It entails the use of formwork moulds and reinforcing steel wires to ensure the concrete is the right shape and size.

Reinforcement Beams for Underpinning

Reinforcing beams – or piles – are driven into the ground or fitted into drilled holes until they’re anchored in stable soil.

Resin Injection Underpinning

With resin injection underpinning, small holes are drilled into the ground around the foundations and filled with environmentally-friendly resin.

Need a Free Underpinning Evaluation?

An experienced Melbourne underpinning contractor will be able to give you a better idea of how long your underpinning job will take – by carrying out a free inspection of your home.

They can also take care of all the preparatory admin work including getting the necessary permits.

Signs of Structural Damage Caused by Subsidence

Structural damage to your home can occur through subsidence when the foundations begin to sink because the earth beneath them has become unstable.

Subsidence is one of the most serious problems a property can suffer. If the foundation can no longer support the weight of your house, it threatens the structural integrity of the building and can slash its resale value.

Spotting signs of damage due to subsidence during the early stages gives you the opportunity to take measures to halt further structural deterioration and prevent similar problems in the future.

You shouldn’t necessarily assume the worst, though. For instance, surface cracks are far more likely to be the result of natural swelling and shrinkage because of humidity and temperature fluctuations. Freshly-plastered walls and ceilings can also develop small cracks as the plaster dries.

Types of cracks that point towards structural damage include those that are:

  • Near windows or doors.
  • Visible outside and inside.
  • Below the damp-proof course.
  • Where an extension joins the house.
  • In your basement.
  • In exterior brickwork.
  • In a chimney.

Other signs of subsidence-related structural damage include:

  • Bowed walls.
  • Gaps between walls and floors.
  • Nails popping out.
  • Wallpaper wrinkling near the ceiling.
  • Windows and doors sticking (the frames may be warping).
  • Uneven floors.
  • Front porch pulling away.
  • Gaps in the exterior of window and door frames.

Getting an Expert Opinion

Unless you’re a structural engineer, the only way to determine whether subsidence is damaging your home is to consult a specialist in foundation and subsidence inspections.

You’ll find that a good underpinning contractor in Melbourne will carry out a free assessment of your property and advise you on any necessary steps to halt progression of structural damage and/or safeguard against problems further down the road.

Concrete Underpinning Vs Resin Injection Underpinning to Fix Subsidence

Cracks in walls near doors or windows can indicate a problem developing with your home’s foundations. Another sign that something’s amiss beneath your house are floors that start to slope.

If the underlying structural issue is subsidence, your foundations are sinking because of unstable soil that’s probably become too dry or too damp.

One of two engineering procedures is typically used by Melbourne underpinning contractors – concrete underpinning or resin injection – to fix the problem by strengthening the base for your foundations.

Concrete Underpinning

Concrete underpinning is the more conventional method to fortify foundations – by extending the depth of the foundation into firmer soil.

It entails digging holes and pouring concrete into them. The concrete is then left to set, creating a new foundation beneath the existing one.

Concrete underpinning is commonly used for smaller jobs. Although a well tried and tested engineering technique, it can be a slow, messy and labour-intensive process. Another potential drawback is that the deeper soil may not be sufficiently solid.

Resin Injection Underpinning

A more contemporary but still proven method of underpinning foundations, resin injection involves drilling small holes into the ground around the foundations and filling them with eco-friendly resin.

The substance expands beneath the foundation and elevates it back into its correct position. The resin also compacts the surrounding soil to prevent expansion or shrinkage. As more resin is injected, it will gradually lift the house above.

Unlike concrete underpinning, resin injection is a fast process requiring little or no excavation.

On the downside, resin injection underpinning may not be cost effective if it turns out there’s a large gap under the ground, which may need a lot of resin to fill it.

Preventing Further Subsidence

Subsidence experts say resin injection holds several advantages over concrete underpinning, including:

  • Speed.
  • Lack of disruption.
  • Versatility.

They point out, though, that for small jobs, concrete underpinning could be the cheaper option.

Both concrete underpinning and resin injections by Melbourne underpinning contractors have been proven to be effective in stabilising the ground underneath a building to prevent further subsidence.