Sealing is the most misunderstood line on an exterior cleaning quote. People assume it is priced like painting a fence: so many square metres, so much product, done. In practice the sealer itself is often the smallest part of the bill. What you are paying for is the preparation, the drying window, the number of coats and the risk the contractor carries if the surface is not ready.
This guide explains what sits behind a sealing price so you can read a quote properly. We do not publish a fixed rate per square metre here, because an honest sealing price cannot be given without knowing the material, the joint condition and how wet the surface currently is. What we can do is show you exactly which variables move the figure, and which ones a low quote has quietly removed.
Preparation is most of the cost
A sealer locks in whatever is underneath it. That means the surface has to be genuinely clean before anything is applied — not brushed over, but washed, treated with a biocide so the algae roots are dead rather than stripped, rinsed, and left to dry through. If organic growth survives under a sealed surface it will continue to feed on moisture in the joints and push the coating off in patches within a season or two.
On block paving there is an extra stage: the joints must be re-sanded with kiln-dried sand and the sand must be dry and settled before sealing. Sealing over damp or partially filled joints is one of the most common causes of a milky, blotchy finish. When a sealing quote looks unusually cheap, the prep stage is almost always where the money has been taken out.
What actually changes the price
- Area in square metres — measured properly, including any paths, aprons and bin standing that you want to match.
- Material — block paving, imprinted concrete, sandstone and porcelain all absorb differently, so coverage per litre varies widely.
- Porosity and age — a dry, thirsty older surface can drink noticeably more product than a recently laid one.
- Sealer type — water-based versus solvent-based, and matt versus satin versus wet-look, all sit at different product costs.
- Number of coats — most surfaces need two; deeply porous concrete sometimes needs a third to avoid a patchy sheen.
- Return visits — sealing usually happens on a separate day to cleaning, because the surface must be fully dry.
- Weather risk — a booked sealing day lost to rain is time the contractor still has to carry.
Why sealing is quoted separately from cleaning
We quote cleaning and sealing as two lines because they are two decisions. Cleaning restores the surface. Sealing is a maintenance and appearance choice on top of it, and it is not right for every drive. A surface that is failing structurally, sinking at one edge or losing its sub-base does not need a coating — it needs the underlying problem dealt with first, otherwise you are sealing a fault in place.
Splitting the quote also protects you. If the clean reveals something unexpected — a large area of spalled concrete, badly cracked pointing, or a drive that turns out to be far more porous than it looked — you can make a decision about sealing with that information in hand, rather than having already committed to it.
Cheap sealing quotes: where the money went
- One coat instead of two, which typically shortens the useful life considerably and often looks uneven in raking light.
- Sealing over a same-day clean, before the surface has dried through — the classic cause of a cloudy white bloom.
- No biocide stage, so growth continues under the coating.
- No re-sanding, so the sealer runs into open joints instead of binding the sand at the surface.
- Thinned product to stretch coverage, which reduces the film left behind.
- No masking of walls, kerbs, borders and drainage, which leaves overspray marks you then live with.
When sealing is worth paying for — and when it is not
Sealing earns its keep on block paving that you want to keep looking freshly laid, on imprinted concrete where the colour has started to wash out, and on any surface where the joints keep losing sand and letting weeds through. It slows colour fade, makes spills easier to lift before they soak in, and keeps the surface easier to wash next time.
It is a weaker case if you are selling within a few months, if the drive is heavily shaded and permanently damp with no drainage fix planned, or if the surface is already near the end of its life. In those situations a thorough clean, a biocide treatment and a proper re-sand deliver most of the visual result at a fraction of the cost.
Be sceptical of anyone who tells you sealing is permanent. Every sealer is a consumable. It wears fastest where tyres turn, at the entrance, and anywhere water sits, and it will need refreshing on a cycle rather than once in a lifetime.
Questions to ask before you accept a sealing quote
- Is the clean, biocide treatment and re-sand included, or quoted separately?
- How many coats, and what is the plan if the surface drinks the first coat unevenly?
- Is it water-based or solvent-based, and what finish will it leave — matt, satin or wet-look?
- How long must the drive stay clear of vehicles and foot traffic afterwards?
- What happens if the weather turns on the booked day?
- Is the price fixed, or an estimate that can move once work starts?