Comparison
Unit Price vs Assemblies Estimating Methods
Use assemblies for speed on repetitive scopes and known building types; use unit price when the owner bids by item, the scope is irregular, or you need to defend the number line by line. Most winning NJ bids blend both.
| Factor | Unit price | Assemblies |
|---|---|---|
| What it prices | Individual items: LF of pipe, each outlet, CY of concrete | Pre-built packages: a wall, a room, a lighting circuit |
| Speed | Slower — every quantity counted individually | Fast — one assembly covers many components |
| Accuracy on unusual scope | High — reflects the actual drawings | Weak — assemblies assume standard configurations |
| Best bid format fit | Owner-unit-price contracts, public works | Stipulated lump-sum, design-build budgets |
| Revision handling | Surgical — change one line item | Rebuild the affected assemblies |
| Defensibility | Every line traceable to a drawing | Requires assembly library transparency |
| Learning requirement | Lower — count and multiply | Higher — assemblies must be maintained |
| Risk profile | Quantity risk on your count | Configuration risk inside the assembly |
Choose unit price when…
- Public unit-price or prevailing wage bid documents
- Irregular buildings, renovations, and unknown conditions
- The owner will audit quantities line by line
- Change orders priced after award
Choose assemblies when…
- Repetitive scopes: apartment units, hotel rooms, office floors
- Early budget estimates before final drawings
- Competitive lump-sum bids where speed matters
- Trade packages you bid every month
Common questions
Which method is more accurate?
Neither is inherently more accurate. Unit price is more transparent; assemblies are more consistent when the library is maintained well. Accuracy comes from matching the method to the scope — most NJ bids we prepare mix assemblies for repetitive areas with unit prices for everything irregular.
Do owners accept assemblies-based estimates?
Yes, for lump-sum bids the format does not matter as long as the total is defensible. For public unit-price contracts, the bid document dictates unit pricing — assemblies can still speed up the internal build before you map quantities to the owner’s schedule.
How do you handle addenda with each method?
Unit price addenda are surgical: adjust the affected lines. Assembly addenda require swapping or scaling the impacted assemblies. We track both in the revision log so your bid team sees exactly what moved and why.
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