> For the complete documentation index, see [llms.txt](https://docs.enercalc.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.enercalc.com/sel-faq/using-the-software/calculation-modules/foundations2/point-load-on-slab/background-on-updates-to-the-p.md).

# Factor of Safety in the Point Load on Slab (PLoS) Module

What the Factor of Safety represents in the Point Load on Slab module and how it relates to ASD and LRFD.

## What does the Factor of Safety represent in this module?

The Point Load on Slab module calculates a nominal load-carrying capacity (Pn) for a slab-on-grade subjected to a concentrated load.

The Factor of Safety (FS) is applied to reduce this nominal capacity for design use.

Users should select a Factor of Safety consistent with their intended performance objectives and applicable engineering judgment.

## What Factor of Safety values are commonly referenced in published research?

Azzi & Laird (2008) commonly applied a Factor of Safety of approximately 3.

Experimental investigations reported by Jlilati, Brown, and Tang (2019) indicate that higher safety margins, on the order of 6, may be appropriate for certain applications.

## How does the Factor of Safety relate to ASD and LRFD?

The referenced values (approximately 3 and 6) are most directly applicable when the method is used in an allowable-stress (ASD) framework.

When LRFD is selected, users should ensure that the combined effect of the strength reduction factor (ϕ) and the Factor of Safety (FS) reflects their intended design assumptions and does not unintentionally result in double-counting of safety margins.


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