When dealing with a foundation lifting repair there are many available options and researching the best solution can be head spinning. Because of this, we are writing this article to hopefully provide you with an unbiased evaluation of two concrete lifting technologies, foam concrete lifting, and foundation piering. We hope after reading this, you’ll be a bit more educated and confident in deciding which technology, or combination of, will be best for your foundation repair project.
Basics of Polyurethane Concrete Lifting
To start, let’s make sure you have a basic understanding of each technology, starting with Polyurethane Concrete Lifting.
Concrete lifting with polyurethane injection is a process that has quickly become one of the most popular options for foundation repair because of its quick, cost-effective, and relatively clean process. It works by injecting a polyurethane through specialized mixing equipment underneath the concrete slab through a hole that has been either drilled through or adjacent to the concrete slab.
Though it administration may seem complex, Polyurethane Injection is quite simple. The three basic steps of concrete raising are:
- Injection: The concrete raising process beings with the polyurethane being injected through a 5/8 inch hole that is drilled through or adjacent to the concrete. Once injected, the polyurethane begins to expand throughout the void space and loose soils.
- Packing: As the polyurethane reacts in the gap, it expands and “packs” in soil and the area around the void. This process is very quick, only taking around 10-15 seconds to complete.
- Raising: Once the polyurethane has filled the void areas, it begins to become confined in the injection zone.During confinement, the polyurethane becomes highly dense until it begins to create lifting pressure in the weakest area, which is your concrete slab. With enough material, the polyurethane can create enough compressive strength and density to lift your slab back to level and grade.
Basics of Foundation Piering
Foundation piers are comprised of two types of piers: Helical and Push Piers. Both of these systems use the same basic principle of using deep soils that are highly dense to create enough torque or tension to create an upward lift.
With Helical Piers, the contractor anchors the helical pier to the building foundation and then spins the pier downward using an auger to twist the system into the ground. Once the helical reaches soil depths that can provide enough torque resistance against the pier, the torque will provide tension against the pier and help lift the foundation upward.
With Push Piers, the piers are driven down hydraulically to depths with highly dense soils or bedrock. Once the Piers are driven to the appropriate depth, the pier can be seated against a bracket on the foundation slab and can be pushed down hydraulically to lift the slab upward.
COSTS: Polyurethane Concrete Lifting vs. Foundation Piering
When it comes to costs, the Polyurethane Concrete Lifting is hands down the cheapest when it comes to small to moderate repairs. The caveat here is that Polyurethane is not a silver bullet and is not always the solution. If your building is experiencing severe settlement then polyurethane concrete lifting may not be an option.
Piering is for heavy-duty work and is designed to provide long-term stability and results. Piering systems tend to come with longer warranties, and they provide more direct measurable results when it comes to lifting pressures and stability than polyurethane systems. But this goes hand in hand when it comes to costs. Polyurethane injection is very reliable when it comes to lifting garages, interior footers, sidewalks, and driveways, or significantly strengthening loose and unconsolidated soils. So the best situation here is to evaluate the complexity of your project to see what solution works best.
LIFTING CAPACITY: Polyurethane Concrete Lifting vs. Foundation Piering
On a standard foundation, piering is going to provide you with the most reliable and the greatest lifting capacity. Piering has the capability of reaching highly dense soils or bedrock at significant depths to leverage your foundation upward. The density is significant and the strength of the piers can be quite robust. However, there are situations where piers are not necessarily the best option. Many large buildings have difficulty with using piers on the interior slabs. These include buildings that do not have interior footers or buildings which are very difficult to install piers on the interior supports. Polyurethane can be a very reliable option for raising or stabilizing these interior slabs. There are many cases in fact where piers have been used to lift the exterior footers, while polyurethane injection is used in conjunction to lift the interior portions.
TIME: Polyurethane Concrete Lifting vs. Foundation Piering
Time is an important consideration when it comes to evaluating these two solutions. Polyurethane injection is a very fast solution. It requires minimal setup, installation, and breakdown, and often can be completed within a day depending on the scope or size of the project. Many polyurethane manufacturers claim you can drive over lifted slabs within 25 minutes after injection.
Piering is a time-intensive and relatively invasive process. To install the piers, the perimeter of the foundation must be excavated to expose the footer so the pier bracket can be installed underneath. The piers are then hydraulically pushed to the appropriate depth. After all of the piers have been installed, they are then each hydraulically lifted to get the foundation up to grade. Afterward, the equipment must be removed, the excavation areas filled, and the landscaping replaced. Now the timing is relative in this instance, because polyurethane may not be able to achieve the lifting capacity that piering is capable of, and so timing may be irrelevant if piering is your only option.
FOOTPRINT: Polyurethane Concrete Lifting vs. Foundation Piering
Foundation piering requires a very large footprint, from excavation equipment to equipment storage to truck access and hydraulic equipment. This takes up a lot of space, takes time, and requires close access.
Polyurethane injection is a self-contained system that can operate out of a box truck. As long as the truck can reach within 250ft of the injection location, the application can be applied. This allows for a small footprint with minimal setup and access to very remote locations.
CAN THEY WORK TOGETHER?
The short answer is yes. When piers lift a building, voids form immediately underneath the slab and those voids must be filled. Polyurethane is an excellent void fill solution and is often used in concert with piers for this reason.
There are additional ways polyurethane and piers are used in concrete lifting:
- Lifting Interior Slabs: There have been many documented projects whereby piers were used to lift outside footers slowly and incrementally. After the exterior is lifted an inch or so, then polyurethane foam is used to evenly lift the interior slabs to match the exterior footer levels. After they are even, the contractor would then dial up the outside and then repeat the polyurethane concrete lift process on the interior. The contractor would continue this process until the interior and exterior are lifted to the goal levels.
- Using Polyurethane to Reduce the Project Cost: Sometimes contractors can reduce the overall project cost by decreasing the number of piers required on the project by increasing the pier spacing and using polyurethane to supplement the lifting process in between the piers. *This should only be done by a foundation lifting contractor with significant experience with both geotechnical polyurethanes and foundation piers.
Both piering and polyurethane have their advantages and disadvantages. The right solution is really dependent on the needs and particular circumstances of your project. In assessing this, you should consult with an experienced foundation contractor or an engineer to help you determine what is the right solution for your needs.