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.
Foundation Repair 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.
Cost Comparison:
Polyurethane injection typically reduces total project cost by 40%–60% compared to steel underpinning, while also completing in a fraction of the time and with minimal disruption to a building owner. In many cases, projects that take days with polyurethane can take weeks with underpinning due to excavation, access, and structural installation requirements.
FOAM FOUNDATION REPAIR COST VS. PIERING COST
The two repairs sit at different price points because they are different amounts of work.
Polyurethane foam foundation repair is priced by the material used and the access required. There is no excavation, the crew is smaller and the work is usually completed in a day.
Piering is priced per pier, and the number of piers is set by the length of foundation needing support and the load it carries. Excavation, ground restoration afterward and a longer schedule add to the cost.
What changes the comparison is depth. Polyurethane cost scales with the volume of void being filled — if the void is large or the settlement deep, the material cost climbs. Piering cost scales with the depth to load-bearing soil. On a shallow problem, polyurethane is markedly cheaper. On a deep one, the gap narrows, and piering may be the only lasting repair.
Any contractor quoting either repair should be able to explain whether your problem is shallow or deep, and why.
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.
WHICH REPAIR DO YOU NEED?
Choose polyurethane foam foundation repair when the settlement is shallow, the void beneath the slab is the main problem, the structure itself is sound, the work needs to be completed quickly, or excavation around the property is impractical.
Choose piering when the load-bearing soil is deeper than injection can reach, the movement is ongoing rather than historical, the structure is heavy, or an engineer has specified a deep foundation solution.
Consider both when the foundation needs stabilizing at depth and the slab inside also needs lifting. The two are not mutually exclusive, and on larger projects they are often used together — piers to stop the movement, polyurethane to fill the voids the movement left behind.
CONCLUSION
Both piering and polyurethane have their advantages and disadvantages. The right foundation repair 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.
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