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Why there's no figure to give you

A service life is a measurement, usually a number of years a coating is expected to keep doing its job before it needs attention. No manufacturer, trade body or independent testing organisation publishes one for these coatings.

A warranty is not that measurement

A warranty term is a commitment to put right a manufacturing defect within a stated period. It is not drawn from testing how long a coating lasts on a patio, a path or a rendered wall. A coating can fail well before its warranty runs out, and a warranty can run out long before the coating actually fails. The two things are answering different questions.

Where the other figures come from

The numbers that do circulate, on tins and in brochures, are a manufacturer's expectation for a product under conditions the manufacturer has chosen. They are not a record of what happened on a specific surface, in a specific garden's weather, under a specific amount of foot traffic.

Before deciding what to coat, it is worth checking what is already on the surface, which the guide on painting paving slabs covers, since an existing coating changes what any new one can be expected to do.

Before you estimate

What decides how long a coating lasts on your surface

No single figure covers this, because each of these changes the answer on its own.

  • Exposure

    A wall or patio facing the prevailing wind and rain takes far more water and UV than a sheltered one, and the two can wear at very different rates even with the same coating.

  • Substrate

    Dense concrete, natural stone, cement render and lime render each take a coating differently, and a lime render in particular can be damaged by the wrong choice.

  • Traffic

    A path used daily by feet, bikes or bins wears a coating faster than a flower bed edge that nobody walks on.

  • Aspect

    North-facing and shaded areas stay damp longer after rain, which changes how a coating behaves compared with a spot that dries out quickly in the sun.

  • Preparation

    How the surface was cleaned, repaired and primed before coating affects how well it grips, regardless of which product went on top.

  • What was already on the surface

    An existing sealant or paint, even one that is not obvious to look at, changes how a new coating bonds and behaves once it is down.

These point to the questions worth asking.

Getting a warranty confirmed in writing

A warranty printed on a tin or a website is a marketing claim until someone at the company has put their name to it in writing. Manufacturers will usually confirm a warranty term by email if you ask them directly, and that email is worth more to you than the wording on the packaging, because it names what the warranty actually covers.

What to ask for

Write to the manufacturer with the specific product name and, if you have it, the batch code. Ask them to confirm the following in their reply:

  • The length of the warranty term, in years
  • Whether it covers materials only, or materials and labour
  • What surface preparation it assumes, and whether a primer or sealer was required for the warranty to apply
  • Whether it's conditional on professional application, or valid for a DIY job
  • What would void it, such as the wrong substrate, standing water, or a missed waiting period between coats
  • Who assesses a claim, and what evidence they'd need from you

Keep the question short and specific. A general question about durability tends to get a general answer back; a question that names each condition tends to get each condition answered.

Reading the reply

Look for conditions rather than for the number of years. A warranty term is only as good as the list of things that can void it, and that list is usually where a manufacturer's letter says more than their packaging does. If the reply mentions a required substrate, a drying window, or a specific primer, compare that against the surface you're actually working on.

A reply that avoids naming the surfaces it covers, or that answers in general terms rather than confirming specific conditions, tells you something too. Where that happens, it's reasonable to ask again, more specifically, or to treat the printed term with more caution.

None of this turns a warranty into a service life. A warranty is a commercial promise about replacement or remedy. The two questions are worth keeping separate, because the second one depends on your exposure, your substrate and what's already on the surface.