What it means
The arrangement involves three parties rather than the usual two. The contractor is the principal, the project owner is the obligee who benefits, and the surety is the company standing behind the promise, which is the reverse of an insurance policy that protects the person paying the premium.
Each of the three bond types covers a different moment. A bid bond guarantees that a winning bidder will actually sign the contract, a performance bond guarantees that the work gets completed, and a payment bond guarantees that subcontractors and suppliers get paid.
Public projects in the United States generally require bonding by statute above a threshold, and large private owners impose the same discipline. Because subcontractors cannot place a lien on public land, the payment bond is often their only route to recovery.
Getting bonded is really a credit approval. Sureties examine the contractor's working capital, net worth, completed project history and the quality of its accounts, and they set an aggregate limit on how much bonded work the contractor can carry at once.
That limit, known as bonding capacity, is what actually constrains growth for many contractors. A firm can win a large job and still be unable to take it, and the cure is usually stronger working capital and cleaner accounts rather than a better bid.
In practice
Real-world examples.
Example
A school district requires a performance bond and a payment bond on a $22,000,000 building. When the contractor fails halfway through, the surety funds a replacement contractor and covers the cost of completion above the remaining contract balance.
Example
An electrical subcontractor is left unpaid for $340,000 after a general contractor becomes insolvent on a federal project. Because the site is public land and cannot be liened, the subcontractor recovers under the payment bond instead.
Example
A growing civils firm wins a $9,000,000 highway contract but is told its bonding capacity tops out at $6,000,000. It brings in a joint venture partner to share the bond and the risk rather than turn the work down.
Formula
Calculation
Premium = contract value x premium rate, normally charged on a sliding scale
Bid bond penal sum = bid amount x the percentage the owner requires
A contractor wins a $5,000,000 project and must post a performance bond and a payment bond, each with a penal sum equal to the full contract value. The surety quotes a tiered rate of 3% on the first $1,000,000 and 2% on the balance, so the premium is (3% x $1,000,000) + (2% x $4,000,000) = $30,000 + $80,000 = $110,000, an effective rate of $110,000 / $5,000,000 = 2.2%.
The bid bond came earlier and cost far less. It was set at 10% of the bid, a penal sum of $500,000, and had the contractor refused to sign after winning at $5,000,000 while the next lowest bid stood at $5,300,000, the owner could have claimed the $5,300,000 - $5,000,000 = $300,000 difference from the surety, comfortably inside that limit.
Whether the bonds could be issued at all came down to capacity. A surety commonly allows work on hand of around ten times working capital, so a contractor with $1,500,000 of working capital may be limited to roughly $15,000,000 of bonded backlog; with $9,000,000 already committed, only $15,000,000 - $9,000,000 = $6,000,000 of room was left, just enough for this job.Case study
Seen in the real world.
The following is an illustrative and entirely fictional example. Thornbury Civils, an invented groundworks contractor, ran a backlog of $9,000,000 against working capital of $1,500,000 and a bonding capacity of about $15,000,000. It then bid, and won, a $5,000,000 drainage scheme that fitted with $1,000,000 of room to spare.
Two months later a client on an unrelated job stopped paying, and $800,000 of receivables aged past ninety days. The surety recalculated working capital, cut the capacity to about $11,000,000, and declined to bond the next contract the fictional firm had already priced and staffed for.
Thornbury's response was to treat the surety as its most important lender. It began sending quarterly accounts unprompted, tightened its retention collection and held a cash buffer purely to protect capacity, on the reasoning that in bonded construction the balance sheet, not the estimate, decides what you are allowed to build.
Watch out
Common mistakes.
- Believing a construction bond protects the contractor, when it protects the owner and subcontractors and leaves the contractor liable to repay every dollar the surety pays out.
- Treating bonding capacity as fixed, when it moves with working capital, receivable quality and the profitability of recent jobs.
- Assuming a performance bond covers defects for years after handover, when its scope is completion of the contract and any maintenance period is usually covered separately.
Questions
People also ask.
What is the difference between a bond and insurance?
Insurance transfers risk to the insurer for a premium, whereas a surety expects no losses and requires the contractor to indemnify it for anything paid on a claim.
How much does bonding cost?
Rates typically run from about 1% to 3% of the contract value on a sliding scale, with the better rates going to contractors with strong balance sheets and long completion records.
Can a newly formed contractor get bonded?
It is difficult without a completion history, though smaller contracts, personal guarantees and assistance programmes for emerging contractors offer a route in.
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