Oil Stain Removal Cardiff

Why pressure washing spreads an oil stain

Concrete and concrete block are porous. Oil wicks in and sits below the surface, held in the pore structure. Water at pressure hits the top of that, mobilises some of it and pushes it sideways and deeper. The stain gets paler in the middle, wider at the edges, and harder to remove than it was before.

The surface around it also gets cleaned at the same time, so the contrast often looks worse afterwards even where the oil itself has not moved much.

Drawing it out instead of pushing it in

The method that works is the opposite of washing. A degreaser is applied neat and worked in to break the oil down, then a poultice, an absorbent paste, is spread over the area and left to dry. As it dries it pulls the dissolved oil up out of the pores and holds it. Then the poultice is removed with the oil in it and the area is rinsed.

Deep or old stains take more than one cycle. We say that up front, because a single application on a stain that has been there five years will lighten it rather than clear it.

What we can and cannot promise

Fresh oil, days or weeks old, usually comes out completely. Months old on concrete usually comes out to the point where you have to know it was there to see it. Years old, especially where the vehicle has dripped in the same spot repeatedly, often leaves a shadow. Hydraulic fluid and gearbox oil are worse than engine oil, and diesel spreads further before it sets.

We will tell you which of those your stain is at the quote, from a photograph if you send one. Nobody benefits from us promising a clear slab and delivering a faint one.

Block paving has an option concrete does not

On block paving, individual blocks can be lifted and turned over, or swapped for spares from an inconspicuous area such as under a car or behind a bin. Where a stain is heavy and localised this is often the better answer than chemistry, and it is permanent. If there are no spares, blocks can sometimes be lifted, cleaned face down and relaid.

Stopping the next one

Once the surface is clean, a breathable sealer makes the next drip a surface problem rather than a pore problem, which means it wipes up. It is worth doing on a driveway where a vehicle parks in the same place, and we can seal at the same visit once the area is fully dry.