Three jobs, three days
“Can you seal my patio?” is a request for three separate pieces of work, and collapsing them into one visit is the root of nearly every failure. Clean, re-sand, seal — each with its own gate before the next can start.
| Stage | $/sq ft | Gate before starting |
|---|---|---|
| Clean and strip old sealer | 0.30–0.55 | Dry weather window ahead |
| Re-sand joints | 0.35–0.70 | Surface dry, joints dry |
| Seal, two coats | 0.90–1.90 | 24–48 h fully dry, no rain forecast |
Cleaning without emptying the joints
The joint sand between pavers is what stops them moving. A wand at close range empties a joint in seconds, and a patio with empty joints shifts, gaps and eventually needs lifting. Work at 1,500–2,500 PSI, keep the fan across the pavers rather than down into the joints, and accept that you will lose some sand — which is why re-sanding is a line item and not an optional extra.
If there is an old sealer on the pavers it has to come off before a new one goes on. Sealing over failing sealer traps the failure underneath, and the result is a hazy, peeling patio that has to be stripped chemically. Check by dripping water: if it beads, there is a coating.
Re-sanding is structural
Polymeric sand is the usual choice: it is swept into the joints dry, the surface is blown clean of every grain, and then it is misted with water to activate the binder. All three steps have failure modes.
- Sweep it fully in. Joints filled two-thirds will settle and look sunken within a season.
- Blow the faces completely clean before wetting. Polymeric sand left on a paver face sets there and hazes permanently.
- Mist, do not flood. A hose on full washes the binder straight out of the joint.
- Let it set before anything else touches the patio.
Polymeric haze is the classic callback
Sealing
Two thin coats, not one heavy one. A heavy coat puddles in the low points, dries to different gloss levels across the patio, and peels where it pooled. The second coat goes on after the first has flashed off, in the window the product’s own data sheet gives.
Sealer types differ in what they promise. A penetrating sealer soaks in and changes the look very little while resisting staining. A film-forming sealer sits on top and gives the wet look customers ask for — and it is the one that fails visibly when anything goes wrong. Ask what they actually want before you pick.
Surface damage risk
PSI & nozzle quick reference
- 0 degRed
- Spot jet. Etches most surfaces.4000 PSI
- 15 degYellow
- Stripping bare concrete.4000 PSI
- 25 degGreen
- General concrete and walkways.3500 PSI
- 40 degWhite
- Siding, wood, vehicles.1500 PSI
- ~65 degBlack
- Detergent draw, low pressure.500 PSI
How seal jobs fail
Every one of these is preventable, and every one of them is expensive:
| Failure | Cause | Cost to fix |
|---|---|---|
| Milky white haze | Moisture trapped under the film | Strip and re-seal |
| Gloss banding | One heavy coat, uneven application | Strip and re-seal |
| Peeling within a year | Sealed over an old failing sealer | Strip and re-seal |
| White bloom returning through | Efflorescence not resolved first | Strip, treat, re-seal |
| Pavers shifting | Joints never properly re-sanded | Lift and relay — a landscaper’s job |
Notice that four of the five are fixed by stripping and starting again. Sealing is the highest-risk work in exterior cleaning, which is why it carries the highest rate — and why the gates matter more than the technique.
Put the cure times on the invoice