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Vegetation near the foundation
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First thing you want to remember is to not lift the house too high-
There are lots of different types of foundation repair. They all have their pluses and minuses. In most cases the contractor is going to install something in the ground that will help prevent part of your foundation from moving down in the future. This is a good thing but it may not solve all of your foundation problems. Foundations can move up and down. So the repairs will probably not address the possibility that the foundation will move up. Also the piers that the contractor will install will only help support the foundation in the immediate vicinity of the pier(s).
Here are some of the more typical approaches:
This has become the most common approach because the material cost is so low. Precast concrete cylinders are pushed into the ground beneath the edge of the foundation. When the resistance of the ground exceeds the weight of that part of the structure then the house will start to lift.
The biggest problems associated with pressed piles are -the need for a relatively stiff foundation and the possibility that most of the pier will not be be very deep. Installing the cylinders can put a lot of stress on the foundation. Older pier and biem foundations and slab foundations with relative shallow perimeter grade beams can be significantly damaged by the installation of the cylinders. If the soil is rocky or stiff the pier may not extend very deep and therefore may not be very stable.
Pros: Relatively inexpensive. Many contractors who can install.
Cons: May not be deep enough. Not approriate for weak foundations.
Steel piers typically consist of steel pipe with a sleeve to enable coupling of segments of the steel pipe. Similar to the press piles, the steel pipe is hydraulically driven into the ground using the weight of the structure as resistance. The pipe is driven into the ground until the resistance of the ground exceeds the weight of the house and the house is lifted. Steel piers tend to be relatively reliable and generally they are installed to a greater depth than most other forms of remedial underpinning.
: founded relatively deep; generally reliable
: fairly expensive and not all contractors install steel pipe piers
Helical piers consist of steel tubing with a flange that enables the pier to be screwed into the ground. The torque used to install the pier correlates with the resistance of the pier. Helical piers are relatively reliable; however, if the ground surface is relatively rocky or the soil is difficult to penetrate with the screw, the pier may not be founded at a depth greater than the active zone.
: reliable for the proper applications; does not induce stress on the foundation to install
: expensive and can only be installed by certain contractors; not appropriate for all applications
Drilled Concrete Piers:
To install a drilled concrete pier, an auger excavates a hole. Commonly, two holes are drilled as the equipment is usually mounted on a bobcat and concrete piers are usually associated with relatively larger disruption in the landscaping near the perimeter of the home and generally there is a delay between the drilling of the holes and the curing of the concrete prior to the lifting of the foundation.
: relatively inexpensive as compared with other underpinning
: messy; delay between installation of pier and foundation lifting; much of the pier is generally located within the active zone
With slab grouting, relatively small holes (ex., 1 inch in diameter) are drilled in the foundation and a soil-cement grout beneath the foundation. As the material is pumped, this can result in lifting of the foundation.
: relatively inexpensive
: difficulty in controlling the grout results in a difficulty in controlling the lift; grouting generally does not improve the stability of the foundation, but can only improve the levelness
With any foundation repair work or repairs where the foundation is lifted, there are a couple of things that should be considered:
Lifting of the foundation can damage the plumbing of the home. Parts of the plumbing are buried in the ground and when the foundation is lifted, this can cause stress on the plumbing, water supply lines, and plumbing drain lines. For this reason, it is prudent to have the plumbing tested following any foundation repair work. It is also good practice to have the plumbing tested prior to the foundation lifting. It is not uncommon for plumbing issues to cause or contribute to foundation problems. If a plumbing leak is contributing to the movement, the repair scheme may need to be altered or delayed.
With the lifting of the foundation, it is good practice to have an elevation survey completed. The elevation survey can serve as a benchmark or reference survey in the event that movement occurs in the future. Foundation contractors will typically provide a warranty for the foundation repair work; however, it is difficult to determine whether the repairs have been affected without a reference survey. Contrary to most people’s perception that with foundation repairs, the foundation is not brought to full level or completely leveled. Usually, the foundation contractor improves the floor surface levelness, but low areas will typically still be lower than most of the other areas of the residence. For this reason, without a reference survey, it is difficult to determine whether the installed piers had failed or whether another area of the house may have shifted, thereby contributing to damage.
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