Oil stains in parkades: a difficult subject. 

Parkade cleanings are a common type of work we doIMG_9601 (1) in the summer months. The drier weather allow us to both power sweeping and pressure washing to get underground areas looking as best as we can. A difficult issue we commonly face are oil stains. While we always want leave a parkade looking as clean as the day it was built, oil stains are a nearly insurmountable challenge for our crews. The key  problem is that concrete’s porous nature, which the oil molecules are able to penetrate the surface and get locked in.
Our two primary cleaning methods have difficulty removing oil stains. Power sweeping really only cleans the surface layer, so it can’t get at the oil. Pressure washing can have substantially more effect, but its still unable to penetrate deeply enough to remove oil. Usually it leaves a stain looking much much better, but we frequently find that a feint outline of the stain remains. That’s partly because oil is insoluble in water, and the pressure washer only removes the discolourations on the uppermost layers. The deeper layers remain, which are almost impossible to remove. It is possible to improve this situation, but it requires several hours per stain applying different chemical treatment methods. Its uneconomical for the building to pay for such a service, and we usually recommend that it is the responsibility of a resident (it usually is for most buildings).