Pipe Pile Allowable Stress in Florida
Why the pipe pile allowable stress in Florida is 0.35 Fy and not 0.5 Fy, what it takes to use the higher number, and how much capacity the difference is actually worth on a real section.
The Short Answer
The default pipe pile allowable stress in Florida is 0.35 Fy, capped at 24,000 psi, for a steel pipe or tube used as a deep foundation element. That is Table 1810.3.2.6 of the 2023 Florida Building Code.
The familiar 0.5 Fy figure, capped at 32,000 psi, applies only where the higher stress is justified under Section 1810.3.2.8. That justification is a filed package: a geotechnical investigation, load tests regardless of the load supported, and a report to the building official from the registered design professional supervising the work.
Pipe pile allowable stress in Table 1810.3.2.6
Item 3 of the table is steel in compression. It gives several conditions, and two of them are routinely confused.
| Condition | Maximum allowable stress |
|---|---|
| Cores within concrete-filled pipes or tubes | 0.5 Fy, capped at 32,000 psi |
| Pipes, tubes or H-piles where justified per 1810.3.2.8 | 0.5 Fy, capped at 32,000 psi |
| Pipes or tubes for micropiles | 0.4 Fy, capped at 32,000 psi |
| Other pipes, tubes or H-piles | 0.35 Fy, capped at 24,000 psi |
| Helical piles | 0.6 Fy, capped at 0.5 Fu |
If a capacity table or a product sheet quotes a structural limit without saying which line it used, it has almost certainly used 0.5 Fy.
What the pipe pile allowable stress difference is worth
On an 8.40 square inch section, which is an 8-5/8 inch outside diameter schedule 40 pipe, the two routes give very different numbers.
| Steel | Default 0.35 Fy | Justified 0.5 Fy |
|---|---|---|
| ASTM A53 Grade B, 35 ksi | about 51 tons | about 73 tons |
| ASTM A252 Grade 3 or A500, 50 ksi | about 73 tons | about 105 tons |
Neither case reaches its psi cap on this section, so the stress ratio governs rather than the cap. On smaller sections in high yield steel the 24,000 and 32,000 psi caps start to bind, and both have to be checked.
What Section 1810.3.2.8 actually asks for
Higher stresses are permitted where supporting data justifying them is filed with the building official. The section lists what that data has to include, and none of it is a formality.
A geotechnical investigation
Under Section 1803. Not a desk study of nearby borings.
Load tests for a higher pipe pile allowable stress
Under Section 1810.3.3.1.2, and the section says regardless of the load supported by the element. There is no small-project exemption.
Direct supervision
Design and installation under the direct supervision of a registered design professional knowledgeable in the field of soil mechanics and deep foundations, who submits a report to the building official stating that the elements as installed satisfy the design criteria.
When the higher pipe pile allowable stress is worth it
When the design load genuinely needs the upper range of the section. If it does not, the filing buys nothing.
Worth deciding at the start of design rather than at plan review. The testing and the supervision both carry cost and schedule.
A simpler way around the pipe pile allowable stress limit
The structural limit only governs if the design load is close to it. Where the working load sits comfortably below the default 0.35 Fy figure, the question never arises and nothing has to be filed.
That is the argument for specifying a larger section at a moderate rating rather than a smaller section run hard. A 32.5 ton allowable working load on an 8.40 square inch section sits below the default limit in every permitted steel grade, so the 1810.3.2.8 package is simply not needed.
The other ceiling on pipe pile allowable stress
Allowable stress is not the only cap on a driven pile. Section 1810.3.3.1.1 states that an allowable compressive load determined by an approved driving formula shall not exceed 40 tons, and that above 40 tons the wave equation method shall be used and loads verified by load test.
A design can clear the structural stress check and still trip that sentence. Both have to be looked at, and they are independent of each other.
Pipe Pile Allowable Stress Questions
Is the allowable stress on a pipe pile 0.35 Fy or 0.5 Fy?
0.35 Fy capped at 24,000 psi is the default in Table 1810.3.2.6 of the 2023 Florida Building Code. 0.5 Fy capped at 32,000 psi applies only to pipes, tubes or H-piles where the higher stress is justified in accordance with Section 1810.3.2.8.
What does Section 1810.3.2.8 require?
Supporting data filed with the building official: a geotechnical investigation under Section 1803, load tests under Section 1810.3.3.1.2 regardless of the load supported by the element, and design and installation under the direct supervision of a registered design professional knowledgeable in soil mechanics and deep foundations who submits a report to the building official.
How much capacity does the higher stress add?
On an 8.40 square inch section it is the difference between about 51 tons and about 73 tons in a 35 ksi steel, and between about 73 tons and about 105 tons in a 50 ksi steel. Whether that is worth the filing depends on how close the design load sits to the default limit.
Do the psi caps ever govern?
Yes. The 24,000 psi and 32,000 psi caps bind on smaller sections in higher yield steels, where the stress ratio alone would otherwise permit more. Both the ratio and the cap have to be checked.
What allowable stress applies to micropiles?
Table 1810.3.2.6 gives pipes or tubes for micropiles 0.4 Fy, capped at 32,000 psi. Micropiles are a separate element type under Section 1810.3.10 and the code requires that they be grouted.
Need the Capacity Check Done Properly?
Send us the loads and the geotechnical report. We will tell you which side of the 0.35 Fy line your design sits on, and whether the 1810.3.2.8 route is worth filing on your project.
(813) 614-1718