Bid alternates are several estimates wearing one cover sheet
In short
An alternate is a separately priced scope branch the owner may buy at award: an add alternate prices scope beyond the base, a deduct alternate prices scope removed from it. Each branch changes quantities, subcontractor scope, duration and time-related general conditions simultaneously, so representing one as a single number typed under the base bid is where the errors begin.
Key takeaways
- A deduct alternate is not the negative of an add: mobilisation, minimum orders and coordination do not come back.
- One alternate moves 6 things at once — quantities, sub scope, duration, general conditions, markup and sometimes bonding.
- Tag conditions with a branch id at takeoff and you price 3 alternates without measuring anything twice.
- Alternates interact. Two that each extend the programme do not add their durations when both are accepted.
- The alternate has to arrive at award as its own record, or the job budget starts from a scope nobody priced.
An alternate is a separately priced scope branch that the owner may or may not buy when the job is awarded. An add alternate prices scope beyond the base bid — the roof terrace, the second lift, the upgraded glazing to Division 08. A deduct alternate prices scope removed from it. On the bid form each one occupies a single blank, and that blank is why alternates go wrong: it looks like a number, and it is an estimate.
Accepting an alternate changes quantities, subcontractor scope, programme duration and every time-related general condition at the same moment. Any one of those, missed, is comfortably larger than the margin carried on the branch. The instructions to bidders normally also state how long the whole bid — alternates included — must remain open, and 30, 60 or 90 days are the usual choices, which means an alternate accepted late is priced on quotes that have already expired.
A deduct is not an add with a minus sign
The most common alternate error is pricing the deduct by flipping the sign on the add. Costs are not symmetric in either direction, and the asymmetry runs one way.
- Mobilisation does not come back. The crew still arrives, the plant is still delivered, the site is still established.
- Design, coordination and shop drawing effort already spent is not recovered by removing the work later.
- Minimum order quantities and restocking terms mean the material saving is smaller than the material quantity implies.
- Removing scope rarely shortens the programme by the time it added, because the removed work was usually running alongside something else.
- An add alternate can extend the programme and push time-related general conditions up, and it can cross a contract-value threshold that changes bonding or insurance.
The working rule: price every branch forward from the base, independently. Never derive ALT-2 from ALT-1 by arithmetic, and never derive a deduct by negating an add.
Six layers one alternate moves at once
| Layer | What changes | The error when it is one number |
|---|---|---|
| Quantities | Conditions are added, and some base conditions are suppressed | Scope the base already carried gets counted twice |
| Subcontractor scope | Some subs price the alternate inside their base, others exclude it | You accept a base quote that already included the work, then add it again |
| Duration | The programme moves by days, not by a percentage | Time-related costs are unpriced on the branch |
| General conditions | Supervision, facilities and temporary works scale with duration | Either omitted entirely or applied twice at the total |
| Markup | Applied per branch or once at the total | Different effective margin depending on which alternates are taken |
| Bonds and insurance | Thresholds are set by contract value | A threshold is crossed and nobody prices it |
Pricing three alternates without taking the set off three times
The structure that makes alternates cheap is a branch tag on every measured condition. The takeoff happens once; the branches are queries over it.
- Take the set off once, tagging every condition as base or as belonging to a named alternate — ALT-1, ALT-2, ALT-3. Conditions that are replaced rather than added carry both tags: the base version and the alternate version.
- Price the base from base-tagged conditions only, so the base total is reproducible without mental arithmetic.
- Compute each alternate as its tag set: quantities added, quantities suppressed, and any condition whose measurement rule itself changes because the condition record carries the unit and waste rules, not the marks on the sheet.
- Re-tag or re-request subcontractor quotes against the same branch names, so a quote line, a MasterFormat cost code and a branch line share one identifier.
- Recalculate duration and time-related general conditions per branch from the programme, never as a percentage uplift.
- Apply markup at the same point in every branch, and record the pairs of alternates whose combination is not additive.
That last step is the one people discover late. Alternates interact: if ALT-2 and ALT-4 each extend the roofing programme by 5 days, accepting both does not add 10 days of general conditions, and accepting both may also move the package from 1 supplier to 2. Only a handful of pairs ever interact on a given job — on a bid form carrying 6 alternates there are 15 possible pairs and usually fewer than 3 that matter — but they have to be written down as combination rules before the bid goes in, because the owner's selection arrives as a combination.
The owner does not buy an alternate. The owner buys a combination of them, and the combination is the thing nobody priced.
Two quantity risks carry into every branch equally and are worth eliminating before branching begins. A scale problem corrupts base and alternate quantities identically, which is why lengths wrong by a consistent percentage is a calibration job first. And a count that behaves differently across sheets will behave differently across branches too, since branches usually live on different sheets — the diagnostic for that is the automated count that finds devices on some sheets and none on others.
Carrying the alternate into award as an object
An alternate does not stop existing when the bid is submitted. It needs to arrive at award carrying its own record: reference and direction (ALT-3, deduct), scope description, the conditions and sub packages it affects, its duration delta in days, its general conditions treatment, its markup rule, a price expiry date, and a state that moves through bid, accepted, rejected or lapsed.
Skip that and the job budget gets built from the base estimate plus a remembered number, which is one of the reliable ways that the awarded budget and the winning estimate stop agreeing on day one. An alternate that spans two trades needs one more field — the interface note saying which package owns which side of it, drawn the way a bid package boundary is drawn — because an accepted alternate with an undefined interface is a scope gap with a price attached.
Keeping several versions of one plan in agreement is an operations-data problem rather than a spreadsheet problem, which is the argument we make about AI in logistics operations and the reason branch tagging is worth automating in AI agents and automation work. The rest of this silo sits under preconstruction, takeoff and estimating, within our wider construction and contracting work.
Frequently asked questions
Short answers to the follow-ups this page tends to raise.
What is an alternate bid item in construction?
It is scope priced separately from the base bid so the owner can decide at award whether to buy it. Alternates let an owner test the market for a wish-list item, or protect a budget by having a deduct ready if bids come in high. For the bidder it means pricing two versions of part of the job under the same deadline, which is why the structure of the estimate matters more on jobs with alternates than on jobs without.
What is the difference between an add alternate and a deduct alternate?
An add alternate prices work beyond the base scope; a deduct alternate prices work taken out of it. The important consequence is that they are not mirror images: removing scope does not return mobilisation, coordination effort or minimum order quantities, so a deduct is almost always worth less than the equivalent add. Price each one forward from the base rather than by reversing the other.
Should general conditions be adjusted for an alternate?
Yes, whenever the alternate changes duration, and that adjustment should come from the programme rather than from a percentage. Time-related general conditions — supervision, site facilities, temporary power, fencing — track weeks on site, so an alternate adding 3 weeks of roofing carries 3 weeks of them. Alternates that change scope without changing duration usually carry no general conditions adjustment at all, and applying a blanket percentage to those overstates the price and loses the branch.
How should alternates be tracked after the bid goes in?
As individual records with a state and an expiry date, not as rows in a submitted spreadsheet. Owners frequently accept alternates weeks after the base award, by which time subcontractor quotes have expired and material prices have moved, so the record needs to say when its price stops being good. Tracking also matters for the budget: the accepted combination, not the base estimate, is what the job budget must be built from.
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The work behind this page
Builds from our portfolio that this page draws on.
GroundUp
A construction project-management command centre for general contractors that keeps schedule, RFIs, budget and the field log in one place — and maps the critical-path recovery the moment a job slips.
Real EstateQuoteForge
An AI CPQ and proposal platform that builds enterprise quotes from your catalog, guards every discount against the margin floor, routes approvals, and generates the proposal.
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