Greenfield norms describe a clean site with good access and no one else working. Almost nothing about a tie-in into a running facility looks like that. The productivity factor is the honest, quantified admission of the difference.
It is also where brownfield estimates go to die. Equipment and materials price much the same whether the plant is running or not. Labour does not, and on a tie-in job the direct labour hours carry most of the risk. An estimator who prices a live plant at greenfield productivity has not produced an optimistic estimate. They have priced a different project.
What eats the hours
The losses are not mysterious. Walk a live plant with a stopwatch and you can name every one of them.
- Permits: hot work, confined space, isolation. Each permit is time the crew stands still, every shift, and the permit office does not work to your schedule.
- Congestion: working around live pipe, cable tray and other trades in a space that was never meant for construction. Two crews in one pipe rack do not each work at half speed; they work at less than that.
- Shutdown windows: the critical work compressed into a few days, priced at overtime, with standby before the window opens and demobilisation after it closes.
- Escorts and inductions: every visitor, every delivery and every new worker slower than on an open site.
- Rework risk: as-builts that do not match what is found once the insulation comes off, and the redesign happening while the crew waits.
None of these show up on a drawing. All of them show up on the timesheets.
How we set the factor
Not one number across the estimate. Each area gets its own factor, built from the specific constraints above, typically landing between 1.3 and 2.2 on direct labour hours, with the reasoning written next to it.
The build-up is additive and boring, which is what makes it defensible. Start from the greenfield norm. Layer on the named losses for that area: so much for permit time per shift, so much for congestion given who else is working there, so much for access and escort. Cross-check the result against actuals from previous work in similar plants, and write the whole derivation in the basis of estimate where a reviewer can challenge it line by line.
A worked example
Take one tie-in area, and call the greenfield content 1,000 direct labour hours of piping work. The area is congested but the plant keeps running: permits cost the crew about ten percent of each shift, congestion with one other trade takes fifteen percent, and escorts and material movement take another ten. The factor comes out at 1.35, so 1,350 hours. At a loaded rate of, call it, 120 dollars per hour, the constraint costs 42,000 dollars on this area alone, and every dollar of it can be explained.
Now take the second area, where the final tie-ins happen inside a ten-day shutdown. The same kind of work runs compressed shifts at premium time, with tighter permits and no room to resequence around a problem. That area carries a factor of 2.0, and it is priced as its own block of work with its own schedule. Blending the two areas into one average factor would hide exactly the thing the owner most needs to see: where the money is exposed.
The shutdown scope deserves more than a factor, in fact. It needs its own estimate, schedule and risk model, which is a subject of its own: see Treat the shutdown as its own project.
A single global factor hides the one area that will actually break the budget.
Where this goes wrong
The global factor. One multiplier across the whole estimate, usually inherited from the last job. It over-prices the easy areas, under-prices the hard ones, and the total looks plausible right up until the shutdown area consumes the margin the open areas never needed.
The factor on everything. The productivity factor belongs on direct labour hours. Applied across materials and equipment too, it silently inflates half the estimate and hands the bid to a competitor who priced the constraint where it actually lives.
The double count. The norms already carried some allowance for site conditions, and the factor gets stacked on top. Know what is inside the norm before multiplying it, or the estimate carries the same caution twice.
The trusted as-built. The factor assumes the drawings describe the plant. In a forty-year-old facility they describe an intention. Survey the tie-in points before pricing them, or carry a named allowance for what the insulation is hiding.
The owner’s part
The biggest lever is not in the estimate at all. It is how much of the scope can be moved out of the congested areas and the shutdown window: pre-fabrication, modular assemblies, early tie-in points installed during earlier outages, temporary bypasses that let work proceed with the plant running. Every hour relocated from a factor-2.0 area to a fabrication shop is bought at a fraction of its site cost. Those decisions, made early, are worth more than any amount of estimating precision applied late.
A brownfield estimate is really a statement about how the work will coexist with the plant. Price the coexistence honestly, area by area, and the number can be defended. Price it with one hopeful multiplier and the plant will issue its own correction, one permit at a time.
Emerald Group prices brownfield and live-plant work for owners, engineering firms and contractors, with the productivity basis documented area by area. If your next estimate has a running facility in the middle of it, get in touch.