Types of Slab-on Grade Repair Piers

There are multiple types of piering systems for repairing slabs. Most companies will tell you theirs is best. The truth is, most systems installed correctly have a very successful track record. Most engineers understand that some systems work better in certain areas than others, but will agree that pressed concrete cylinders work great, so do steel piers and drilled piers. Dig a little deeper into the subject of different pier systems and you will find out that of all of them, pressed concrete cylinders are more universal in their application. They are the least expensive and have 10’s of 1,000’s of successful applications in homes over the last 20 years. Engineers like the fact that they are placed under the foundation beams where most other systems are placed outside of the beams and have hangers on the foundation.

Pressed Steel Piers

This type of pier works well in areas where bedrock can be reached. It is more expensive than pressed concrete cylinders, so many firms sell fewer piers than your home might need, spreading them too far apart so the bid can be accepted. If you ever see a home with a scalloped look to the fascia, that home probably has pressed steel piers.

Installers use the house’s weight as resistance to press interlocking steel segments into the ground on the outside edge of the foundation. Steel piers can reach much deeper depths than other systems. This makes sense because they are less than ½ the width of concrete cylinders and have smooth surfaces. They need to hit bedrock to be successful. Once the pier is driven to refusal, the top segment of the pier is attached to the foundation with a bracket.

The advantages of steel piers are that they are less invasive to the property to install. They go deeper than other systems and they are installed in a minimal amount of time.

The disadvantages of steel piers is that they are expensive. So often they are spaced too far apart. They need to hit bedrock so they are not appropriate for all areas. They are not installed under the foundation, but on the side of it and they are corrosive.

Drilled Bell Bottom Piers

Bell bottom piers are the most thoroughly tested foundation repair method. They have the longest track record of all the systems on the market today. If installed correctly and at the right depth, they have an excellent track record. Bell bottom piers get their name because in profile, they look like a bell at the bottom. Basically they are a drilled hole with a widened foot at the bottom. Rebar is placed inside the hole and concrete is poured to the top with a widened cap. The belled foot is the part of the pier that does all the work. When this type of pier is not correctly installed and there is failure, it can be an intensive and expensive repair problem. Installing this type of pier correctly requires many steps and procedures. This is one of the biggest downfalls because this all takes time and has a greater cost. Bell bottom piers are the most expensive type of system. The process requires soil testing. Heavy equipment drills holes that create a lot of soil that must be hauled away. Installation requires more time than any other system. Drilled bell bottom piers should only be installed as a required solution as an engineers recommendation.

Bell bottom pier advantages include: no damaging forces exerted on the home, with proper engineering and installation, the correct depths will achieve long term results.

Bell bottom disadvantages include: Expensive, several weeks of down time, very invasive to your property and poor engineering or depths of piers will cause seriously expensive problems.

Pressed Concrete Piers

We like concrete piers made of pressed segments of concrete cylinders. This type of repair system is the most widely installed in Texas. The concrete cylinders can be solid or have 5/8” holes in the middle. Some firms that use the hole style cylinders say that they use the hole to install a cable or a piece of steel to keep the cylinder aligned as they press them in. This is mostly a marketing idea to differentiate themselves from other firms as most engineers will explain that the hole in the cylinder actually weakens the cylinder and the tensile strength that these firms say their piers have is not required and not proven. The hole can actually provide a highway for surface water to penetrate to the bottom of the pressed cylinder causing failure. We only use solid concrete piles and install these very accurately with great success.

Concrete piers are pressed into the soil using the weight of the structure as resistance. As they are pressed down, another cylinder is placed on top of the first. These piers are pressed to absolute refusal, by either hitting bedrock or when the weight of the structure cannot push them any further. This type of pier does not require being on contact with bedrock, they work by surface friction on the soil that they have penetrated. Concrete cylinders are placed under the foundation beams and can be installed under the interior portion of the structure as well. Because these piers are less expensive to install, more piers per job can be afforded. Remember, your home is a slab-on-grade foundation. When it is raised by foundation repair, it is now an elevated slab. The more point loads you provide, the less the span deflection, which is a good thing. Each pier is pressed bearing many times the weight it will actually carry as multiple piers will share the load simultaneously when all the piers used are in place and supporting the load. This is why this system is applicable to so many different situations.

Pressed pier advantages include: Being very reliable, the most cost effective system, are installed relatively quickly, they are installed beneath the foundation, not next to it and can be installed under the interior of structures to create “as-built” level condition to the slab. Pressed cylinders install with minimal damage to the landscape.

Some of the disadvantages of pressed concrete piles include: They do not provide up lift resistance similar to bell bottom piers and they can be a slightly more invasive installation than steel piers.

Douglas Foundation Repair - 12510 Edwards Hollow Run - Austin, Texas 78739