Key points
- Material, workmanship and insurance-backed guarantees are three separate documents from three different people.
- A BBA certificate assesses a product; it is not a guarantee and gives you no right to a repair.
- Unregistered guarantees, fixings through the membrane, incompatible repairs and lack of maintenance are common reasons cover fails.
- Get every guarantee's issuer, length, cover, conditions and transferability in writing before you sign.
What guarantees can you get on a flat roof?
There are three main types, and they are separate documents. A material guarantee comes from the membrane manufacturer and covers the product. A workmanship guarantee comes from the roofing contractor and covers how it was installed. An insurance-backed guarantee is an insurance policy that protects the workmanship guarantee if the contractor can no longer honour it.
| Material guarantee | Workmanship guarantee | Insurance-backed guarantee | |
|---|---|---|---|
| Who issues it | The manufacturer | The roofing contractor | An insurer, arranged through the contractor |
| What it covers | Defects in the product itself | Faults in how the roof was installed | Usually the workmanship guarantee if the contractor stops trading |
| Typical conditions | Registration, a specified build-up, sometimes an approved installer | The terms set out in the contractor's quote | Policy terms, a premium, and registration of the job |
| Main limit | Rarely covers installation errors | Only as strong as the contractor behind it | Cover limited to what the policy says |
Lengths vary by product, specification and contractor, and should be set out in writing for each document.
What does a manufacturer's material guarantee cover?
It covers failure of the product, such as a membrane that degrades early because of a manufacturing defect, provided it was installed and maintained as the manufacturer requires. It does not normally cover a lap that was badly bonded or an upstand that was too short, because those are workmanship faults.
Some manufacturers offer more than one level of guarantee. The basic level covers materials only. Higher levels, often called system guarantees, may also cover the labour to put a defect right, but usually only where the full system was used, the build-up matches their specification, the installer is approved by them and the job was registered, sometimes with an inspection.
Manufacturer material guarantees are available on many of the systems we install, including EPDM, GRP and single-ply, and we register them for you where the system allows.
What does a workmanship guarantee cover?
It covers faults caused by how the roof was put on: poor bonding, laps, upstands, trims and outlet details, and the contractor's promise to come back and put them right. It is the guarantee that matters most in practice, because most flat roof leaks start at details formed on site rather than in the membrane itself.
We give a written workmanship guarantee on every re-roof, with its length set out in the quote. Whoever you use, check what the guarantee covers, whether it includes making good any internal damage, how to report a fault, and what happens if the roof is altered later.
A workmanship guarantee is only as strong as the business behind it. If the contractor stops trading, the guarantee usually stops with it, which is where insurance-backed cover comes in.
What is an insurance-backed guarantee?
It is an insurance policy that steps in to honour the contractor's workmanship guarantee if the contractor has ceased trading and can no longer do so. It does not usually pay out simply because the roof has a defect while the contractor is still around and able to fix it.
Policies are normally bought for a single job with a one-off premium, and the cover, length and exclusions are set by the insurer, not the contractor. Before relying on one, ask:
- who the insurer is, and whether the policy is issued in your name;
- whether it covers the full workmanship guarantee or only part of it;
- whether it transfers to a new owner if you sell;
- what the premium is, shown as a separate line on the quote.
Ask us about insurance-backed guarantee options when you book a survey.
Is a BBA certificate a guarantee?
No. A BBA certificate is an independent assessment of a product, not a promise to you. It records how the product performed under assessment, including an expected service life where installed and maintained as described, and some certificates also cover fire performance or wind resistance.
That is useful when comparing systems: one BBA assessment of an EPDM membrane, for example, puts its life at 35 years or more. But a certificate gives a homeowner no right to a repair if the roof fails, and it says nothing about how well a particular roof was installed.
Treat a certificate as evidence that the product is sound, and a guarantee as the document that says who fixes it. The flat roof lifespan guide covers service lives for each system.
What can void a flat roof guarantee?
Breaking the guarantee's conditions, most often through something done to the roof after it was finished, can void it. Typical exclusions and conditions include:
- Not registering it. Many manufacturer guarantees must be registered within a set time after completion.
- Alterations by others. A satellite dish, aerial, solar bracket or cable fixed through the membrane by someone else.
- Repairs with the wrong materials. Sealant, bitumen paint or a coating that is not compatible with the system.
- Using the roof for something it was not designed for. Foot traffic, furniture or plant pots on a roof not built as a terrace.
- Lack of maintenance. Blocked outlets or gutters that cause ponding and overflow.
- Damage from outside events. Storm damage, fallen branches, fire and structural movement of the building are usually excluded.
- Unpaid accounts. Some guarantees only take effect once the final invoice is paid.
Our flat roof maintenance guide covers the routine care most guarantees expect.
What should you ask for in writing?
Ask for the guarantee terms before you sign, not after the roof is finished, so you can compare quotes on the same footing. A checklist:
- Which guarantees are included: material, workmanship, insurance-backed, or a combination.
- Who issues each one, and how long each one runs from completion.
- What each covers: materials only, labour to put defects right, internal damage.
- The system and build-up being installed, and confirmation that it meets the manufacturer's requirements for the guarantee offered.
- Who registers the guarantee, and when you will receive the certificate or reference.
- Conditions you must meet, such as maintenance or inspections.
- Whether the guarantees transfer to a new owner.
- How to report a fault and what response to expect.
Keep the paperwork with your house documents, along with any building control completion certificate. When you sell, the buyer's solicitor will usually ask for both.
Does a better guarantee cost more?
Sometimes, because guarantee conditions shape the specification. A system guarantee may require the manufacturer's full build-up, its own trims and adhesives and an inspection, which can cost more than a basic specification, and an insurance-backed policy carries a premium.
Guide prices, including VAT, for a 20 m² extension roof with a new deck and warm-roof insulation:
| System | Guide price |
|---|---|
| Torch-on felt | £2,700–£4,700 |
| EPDM rubber | £2,800–£4,900 |
| GRP fibreglass | £3,000–£5,400 |
These are guide prices; the fixed price comes after a free survey and the written quote sets out which guarantees apply. See the EPDM vs GRP vs felt guide, the cost guide, or start with the guide-price tool.
Does a guarantee help if the roof is already leaking?
Only if the guarantee is still in date, the fault is the kind it covers and its conditions have been met. Start with the contractor who installed the roof, give them the guarantee reference and dates of the leak, and let them inspect before anyone else works on it, because a repair by another firm can end the cover.
If the original contractor has stopped trading, check whether an insurance-backed policy exists. If there is no usable guarantee, a survey and leak trace will find the cause before you decide on a repair or a replacement. The flat roof leaks guide explains what to do meanwhile.
More questions
Is a manufacturer's guarantee enough on its own?
Rarely. It covers the product, while most problems come from how the roof was installed, so you also want a written workmanship guarantee from the contractor.
Can I transfer a flat roof guarantee when I sell my house?
Some guarantees transfer automatically, some need the new owner to be registered and some do not transfer at all. Check the wording and keep the certificates for the buyer's solicitor.
Does a BBA certificate mean the roof is guaranteed?
No. It is an assessment of the product's performance and expected life, not a guarantee, and it gives you no right to a repair if the roof fails.
Will fixing a satellite dish to my flat roof affect the guarantee?
It can. Fixings through the membrane by anyone other than the roofer are a common exclusion, so ask the roofer to form a proper detail or use a non-penetrating mount.