A lot of paving and path enquiries start the same way: "it's looking pretty rough, does it just need a pressure wash?" Sometimes the answer is yes — grime, moss and general weathering are cosmetic problems that clean up well. But sometimes what looks like a dirty path is actually a path with a failing base underneath, and a pressure wash on that kind of problem just makes it look temporarily better while the underlying issue keeps getting worse. Here's how to tell the difference before you spend money on the wrong fix.
Cosmetic issues — a clean or reseal usually sorts these out
Surface staining, grime and general dullness. Built-up dirt, algae and general weathering that hasn't changed the shape or level of the paving is almost always cosmetic. If the surface is flat, stable and even under the grime, a proper clean (and a reseal if it's due) will usually bring it back.
Moss and mould in shaded or damp areas. Common on south-facing paths and anywhere water sits after rain. Unsightly, but not structural on its own — though it's worth checking why that area stays damp, since ongoing moisture is also a contributor to base problems over time.
Faded or patchy colour. UV exposure and weathering fade pavers unevenly over years. This is a purely visual issue and doesn't indicate anything wrong underneath.
Signs of an actual base failure — these need more than a clean
Sinking, dipping or uneven sections. If you can see or feel a section of the path that's noticeably lower than the pavers around it, that's the base underneath moving or eroding — usually from poor compaction when it was originally laid, water washing out the bedding material, or tree roots disturbing the ground. Cleaning the surface won't touch this.
Individual pavers rocking or shifting underfoot. A paver that moves when you step on it has lost its support from below. Left alone, the movement accelerates — it works the joints open, lets more water in underneath, and the problem spreads to neighbouring pavers.
Widening gaps or cracking joints. Some joint movement is normal, but gaps that are clearly widening over time, or cracks running through multiple pavers in a line, usually point to ground movement underneath rather than a surface problem.
Pooling water that wasn't there before. If water is now sitting in a spot it never used to, the grading or base has shifted. Standing water sitting on paving also accelerates base erosion, so this tends to get worse the longer it's left.
A path or patio that's visibly separating from a step, slab or the house. A gap opening up where paving meets a fixed structure is one of the clearer signs of base settlement, since the paving is moving independently of something that isn't.
Why the distinction matters
Pressure washing a cosmetically dirty path is a quick, low-cost job. Pressure washing paving that's actually suffering from base failure doesn't fix anything — it can even make sinking or shifting pavers more obviously loose, and in some cases the water used in the clean adds to the moisture problem that caused the base issue in the first place. Getting the diagnosis right up front saves paying for a clean that doesn't hold, and then paying again for the repair that was actually needed.
What to do if you're not sure
If your paving is just dirty and stable, a clean is a straightforward job. If you're seeing any sinking, rocking pavers, widening gaps or new pooling, it's worth having it looked at properly rather than guessing — a base issue caught early is a much smaller repair than one left to spread across a larger section of the path.