Interior selective demolition shifts generator planning from one large feed to a set of small, varied loads spread across a building that is still standing. A full teardown usually has its utilities cut off and needs one or two large units placed in the open. A selective job often keeps part of the building live, so the generator has to serve many rooms, avoid exhaust and dust problems indoors, and stay within noise and hours limits. The planning questions move from “how big” to “where, how many circuits, and for how long each day.”
OSHA addresses utilities before demolition in 29 CFR 1926.850(c), which states that electric, water, steam, sewer and other service lines shall be shut off, capped, or otherwise controlled, outside the building line, before demolition work is started. That wording sets the baseline for a full teardown. When part of a structure stays in service, what is shut off and what stays live depends on the scope, the contract and the competent person’s survey, so confirm the plan with your safety lead before sizing anything. Stag Power Rentals supplies diesel generators from its Dickinson, TX yard in a fleet that runs from 20 kW to 2000 kW, which covers both ends of this comparison.
Full teardown and interior selective demolition side by side
The table below sets the two job types against the factors that drive generator planning. It describes typical patterns, and any single project can differ, so treat each row as a prompt to check against your own scope. The point is that the same demolition crew can face very different power questions depending on whether the building comes down or stays.
| Planning factor | Full teardown | Interior selective demolition |
|---|---|---|
| Building status | Comes down, usually vacant | Partly or fully stays standing, sometimes occupied |
| Utilities | Typically controlled or shut off before work starts | Some systems often stay live, depends on scope |
| Load profile | Fewer, larger loads such as pumps, lighting towers and heavy tools | Many small, varied loads such as hand tools, dust collection, lighting and temporary power |
| Work areas | One site, often open | Many rooms and floors, sometimes separated by containment |
| Generator placement | Outdoors, near the work | Outdoors by default, with cables run inside |
| Dust and exhaust | Managed with site layout | Managed with containment, ventilation and exhaust routing |
| Noise and hours | Depends on site and local rules | Often tighter, especially next to occupants |
What changes when utilities stay live
In a full teardown, the generator is usually the main power source for everything that remains. In a selective job the building supply may still feed occupied or protected areas, so the rental unit becomes a second system that has to stay clearly separate from it. If the plan is for the generator to back up a live part of the building, a transfer switch keeps the two sources from connecting to each other. Who installs and approves that connection depends on the electrical contractor, the building owner and local requirements.
Smaller loads, more of them
Selective demolition leans on cutting, drilling and handheld tools, plus dust collection and work lighting, instead of a few heavy machines. Each load is modest, but they start and stop in no steady pattern, and several areas may draw power at once. Building the load list room by room, as covered in the construction site generator sizing guide, gives a clearer picture than a single total. Motor-driven equipment may need starting capacity above its running figure, so check nameplate data instead of assuming.
Placement: indoors versus outdoors
Diesel exhaust and heat are the main reasons generators are normally kept outside an occupied or enclosed building. Selective demolition adds dust, and a unit pulling in dusty air or exhausting near an air intake can create problems for both the machine and the people nearby. Where an interior location is proposed, ventilation, exhaust routing and carbon monoxide controls are matters for your safety lead and the project’s requirements, not for a rental quote. A common approach is to place the unit outdoors, away from doors, windows and air intakes, and run feeder cable to the work area.
Distribution to many small work areas
One generator rarely serves ten rooms through a single cable. Distribution equipment splits the feed into branch circuits, so each area gets its own protected outlets, and a fault in one room does not shut down the rest. Stag’s power distribution equipment is the starting point for that layout. Planning cable paths early also keeps cords out of egress routes and away from the debris stream.
Noise and hours
If occupants are nearby, work hours may be limited by the lease, the owner or local ordinance, and generator noise counts against those limits. Shorter permitted hours change the rental picture as well, because Stag bills by single, double or triple shift. A job restricted to one daytime shift may fit single-shift billing, while a job running extended hours would not, so confirm the shift pattern with Stag before the unit is scheduled. How shift pattern and duration enter a bid is covered in how a demolition bid should account for temporary power.
Questions to settle before ordering
The list below turns the comparison into a pre-order checklist. Answers will differ by project, and some depend on documents you do not control, such as the lease or the owner’s rules. Work through them with the project manager, the electrical contractor and your safety lead. The pre-demolition power checklist covers a related set of items, from the utility disconnect record to the exit plan.
- Which building systems stay live, and which are shut off or controlled?
- Does the generator back up any live area, which would call for a transfer switch?
- What loads run in each work area, and which start at the same time?
- Where can the unit sit outdoors, clear of intakes, doors and occupied space?
- How many branch circuits and cable runs does the distribution layout need?
- What noise and hours limits apply, and how many shifts will the unit run?
For a full-teardown comparison, see Stag’s demolition site generator rental guide. For work inside an occupied structure, the renovation and remodel guide covers related ground.
Planning the rental with Stag
Selective demolition rewards a short planning conversation before the generator is delivered, because the building decides most of the answers. Stag Power Rentals can discuss unit size from 20 kW to 2000 kW, distribution and shift billing against your load list and site limits. Our construction overview shows how we support jobs like this, and you can send your scope through the quote request form when the load list is ready.
Frequently Asked Questions
Is a generator for selective demolition sized differently than for a full teardown?
Often, yes. Selective jobs tend to have many smaller loads across several rooms, so a room-by-room load list matters more than a single large figure. Starting capacity for motors still needs checking.
Can a diesel generator run inside the building during selective demolition?
That depends on the site, the ventilation and your safety requirements. Diesel exhaust is a concern in enclosed spaces, so many projects place the unit outdoors. Confirm with your safety lead.
Do I need a transfer switch for selective demolition?
Only if the generator will back up or connect to a live part of the building. Confirm the design with the electrical contractor and building owner.
How does shift billing affect a selective demolition rental?
Stag bills by single, double or triple shift, so the hours you are allowed to work influence which shift pattern fits. Confirm the pattern with Stag when you request a quote.
Does OSHA require utilities to be shut off before demolition?
OSHA 1926.850(c) says service lines shall be shut off, capped or otherwise controlled outside the building line before demolition starts. How that applies when part of a building stays in service depends on the project, so confirm with your safety lead.