Collateral Warranties: Why You Keep Getting Asked to Sign Them

‍‌‌‌​​‌‌​​​​​​​‌‌‌​​‌‌‌​​‌​‌‌​​‌‌‍On a typical job, you have a contract with the employer or main contractor. The funder, future buyer or tenant is not a party to that contract, so under the old privity of contract rule they can't sue you on it.

Collateral warranties (and third-party rights under the Contracts (Rights of Third Parties) Act 1999) are the bolt-ons that create a direct link so those third parties can come after you if something is wrong with the building.

1. What a collateral warranty actually is

A collateral warranty is a separate contract, "collateral" to your main contract or appointment.

In practice:

• You (contractor, consultant, or design subbie) are the warrantor.

• A funder, purchaser, tenant, or sometimes the client themselves is the beneficiary.

• You warrant to that beneficiary that you have carried out / will carry out your services or works in accordance with your underlying contract, often with an explicit duty of reasonable skill and care (or sometimes higher).

• The warranty gives the beneficiary a direct contractual right to sue you if defective design/work in your package causes them loss.

Without that warranty (or express third-party rights), they'd have to try their luck in negligence, which is harder and often gives a narrower range of recoverable losses.

2. How third-party rights fit in (and how they differ)

The Contracts (Rights of Third Parties) Act 1999 lets parties to a contract give enforcement rights to named third parties without a separate warranty.

So instead of:

• main contract + 20 separate warranties to funders/tenants/buyers,

you can have:

• main contract with a third-party rights schedule saying "X funder / tenants can enforce clauses A, B, C of this contract".

Key differences in feel:

• Collateral warranties = separate contracts to sign, often mirroring the main contract obligations.
• Third-party rights = rights built into the main contract, often seen as lighter admin.

On a lot of projects, contracts exclude the 1999 Act by default to avoid random third-party rights; if rights are wanted, they're carved out specifically in a schedule.

From your perspective, both mechanisms do the same thing: they create extra people who can sue you. The debate is more about paperwork preference than substance.

3. What a warranty usually commits you to

Standard forms vary, but most collateral warranties for contractors and consultants include things like:

• A warranty of skill and care -- that you've performed your works/services with reasonable skill and care or in line with the main contract/appointment. Sometimes this is tightened in ways that edge towards strict "fitness for purpose" -- watch for that.

• An obligation to maintain professional indemnity insurance at a stated level for a set period (for designers/consultants, and D&B contractors).

• Step-in rights for funders -- they can "step into" the employer's shoes if the employer defaults or the contract is terminated, to keep the project alive.

• Limitations on liability -- often mirroring caps, exclusions and net contribution clauses in your main contract, but sometimes those are missing or watered down in the draft warranty.

• Restrictions on assignment -- how many times and to whom the beneficiary can transfer the warranty (e.g. to a purchaser/tenant).

You want the warranty to match your main contract risk profile, not secretly extend it.

4. Why clients and funders push so hard for them

From their side, warranties and third-party rights are project security:

• They give funders/end purchasers/tenants a direct route to recover if there are serious defects -- especially if the employer/SPV or main contractor goes bust.

• They help with funding and exit: lenders and investors often won't fund a scheme or buy a building unless they have a full "warranty package" from the main contractor, key subs and designers.

For you, that means: no warranties, no deal, on a lot of commercial projects. The trick is to manage what you promise, not refuse the whole idea.

5. How to protect yourself when you're asked to sign

You won't get away from collateral warranties on serious jobs, but you can sign them with your eyes open.

Check and push for:

• Consistency with your main contract/appointment -- the warranty should not impose higher duties than your original deal (for example, no surprise "fitness for purpose" when your base appointment is skill and care only).

• Same caps and time limits -- liability caps, PI levels, limitation periods and exclusions in the main contract should flow through into the warranty. You don't want uncapped exposure to a beneficiary when you're capped to the employer.

• Reasonable PI obligations -- if they want you to maintain PI at a level that's unrealistic or unavailable in the market, you're setting yourself up to breach.

• Who gets warranties / rights and how many -- list the categories (funder, first purchaser, first tenant) and any limit on the number of assignments, so you don't have an endless queue of potential claimants.

• Third-party rights vs separate warranties -- if you're drowning in paperwork, consider pushing for a single third-party rights schedule instead of dozens of near-identical warranties -- but still check the risk profile is the same.

In short: a collateral warranty is not "just a formality". It's another contract that can come back to bite you years later. Treat it like that when you're negotiating and signing.

Collateral warranty / third-party rights quick-check

Before you sign, ask yourself:

• Who's getting rights? Funder, buyer, tenant -- and how many separate beneficiaries/assignments are allowed?
• Does it match your main contract/appointment? Duties, caps, exclusions and law should line up -- no "upgrade" to your liability.
• Skill and care or fitness for purpose? Check the wording -- anything that smells like "guarantee" or "fit for purpose" needs careful thought (and usually pushing back).
• PI obligations realistic? Required level and duration match what you can actually buy and keep in place.
• Term and limitation clear? Warranty shouldn't keep you on the hook longer than the main contract, unless you've priced and agreed that.
• Rights created via warranty or third-party rights schedule? Either is fine -- you just want clarity and consistency, not a surprise second set of harsher terms.

If you can't tick most of that, hit pause and get it re-drafted -- you're signing a fresh contract, not a harmless side letter.

Disclaimer: SiteKiln gives you plain-English information, not legal advice. Talk to a solicitor before making big decisions on live disputes.

What to do next

• Before signing any collateral warranty, check whether the duties match your main contract -- no surprise upgrades to fitness for purpose if your appointment is skill and care only.
• Make sure liability caps, PI levels, limitation periods and exclusions from your main contract flow through into the warranty.
• Check that the PI insurance level and duration they want you to maintain is realistic and actually available in the market.
• Find out who gets warranties, how many beneficiaries there are, and how many times the warranty can be assigned.
• If you are drowning in near-identical warranties, suggest a single third-party rights schedule under the Contracts (Rights of Third Parties) Act 1999 instead.

Sources

• Contracts (Rights of Third Parties) Act 1999 -- https://www.legislation.gov.uk/ukpga/1999/31/contents
• Limitation Act 1980 -- https://www.legislation.gov.uk/ukpga/1980/58/contents

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