Most commercial cladding gets cleaned when somebody senior finally notices it. A director visits the site, sees streaking down the elevation, and the job goes on a list. That is usually years later than it should have been, and by then the question is no longer whether the building looks tired. It is whether the coating is still doing its job.
Dirt that sits on the panel, and dirt that eats it
Cladding soiling falls into two broad groups, and they behave very differently. The first is atmospheric deposit: traffic film, general particulates, dust thrown up from yards and access roads. It is unsightly, it dulls colour, and it washes off. Left alone for a decade it will hold moisture against the surface, but on its own it is not destroying anything.
The second group is the one that matters. Organic growth such as algae, lichen and moss does not simply rest on the surface. It holds water permanently against the coating and, in the case of lichen, actively bonds into it. Add run-off staining from oxidising fixings, sealant bleed, or bird fouling with its acidic content, and you have soiling that is chemically working on the finish rather than sitting on top of it.
The practical test is simple. If a wet cloth wiped down a low panel lifts most of the discolouration, you are dealing with deposit. If the marking stays, or the panel underneath has visibly lost its sheen compared with a sheltered area, the coating is already being affected.
Why the north elevation always looks worst
On almost every industrial unit in the UK, the north and north-east elevations are visibly dirtier than the rest of the building. That is not coincidence. Those faces get the least direct sun, stay damp longest after rain, and therefore give algae the conditions it needs. Prevailing south-westerly weather also drives rain and airborne matter onto specific faces.
This is worth knowing because it changes how a clean should be specified. Treating all four elevations identically is usually the wrong call: the sheltered faces may need little more than a rinse, while the shaded faces need a biocidal treatment with proper dwell time. A contractor quoting a single blanket rate per square metre across the whole envelope has not looked at the building properly.
Pressure is the least important part of the specification
There is a persistent assumption that cladding cleaning means high pressure. On coated steel and aluminium composite it usually means the opposite. Excessive pressure will drive water behind panel joints and through sealant lines, force it into insulation, and on older or already-degraded coatings it will strip the finish entirely. Once the coating is broken, the substrate corrodes and the panel is on a much shorter clock than it was before it was cleaned.
A competent specification leads with chemistry and contact time, not force. A suitable detergent or biocide is applied, given time to work, agitated where needed, and then rinsed at controlled pressure. The cleaning is done by the product; the water removes what the product has released. Where a manufacturer's warranty is still live on the cladding system, the permitted cleaning method is very often written into it, and using the wrong approach can void it.
The sequence also matters. Working top-down keeps dirty run-off from re-soiling cleaned areas, and it means the rinse of an upper section becomes part of the pre-wet of the section below.
- Establish the panel type and coating before anything else
- Check whether a system warranty is still in force and what it permits
- Test a discreet area and inspect it once dry, not while wet
- Lead with dwell time and appropriate chemistry, not pressure
- Work top-down and control where the run-off goes
Access is usually what drives the programme
On a single-storey unit with hard standing all round, access is straightforward and the job is largely about method. On a live retail or distribution site it is rarely that simple. Elevations back onto service yards that need to stay operational, loading doors cannot be blocked, and the areas that most need cleaning are frequently the ones hardest to reach.
The realistic options are powered access, telescopic pole systems, or rope access, and each has a different cost and disruption profile. Pole systems reach useful heights without a machine footprint, which suits tight yards. Powered access gives better control and inspection at height but needs ground conditions that will take it and a footprint that does not strand a delivery bay.
This is the single biggest reason two quotes for the same building can differ enormously. They are often not pricing the same access strategy, and the cheaper one may be assuming a level of site closure the client will never agree to.
Run-off, drainage and the part that gets sites into trouble
Cleaning a large elevation produces a lot of contaminated water carrying detergent, biocide, and everything that was on the panel. Where that water goes is a regulatory question, not a housekeeping one. Discharging it to a surface water drain can constitute a pollution offence, and on industrial estates surface water frequently runs straight to a watercourse.
A properly planned job establishes the drainage layout before a hose is connected, identifies which gullies are foul and which are surface water, and protects or bunds accordingly. On sensitive sites that can extend to interceptor mats or vacuum recovery of wash water. It is unglamorous, it adds cost, and it is the difference between a routine maintenance job and an incident that involves the client's environmental team.
What a sensible cleaning interval looks like
There is no universal figure, because exposure varies so widely. A unit on an exposed rural estate surrounded by trees will grow algae far faster than a sheltered urban building. What is consistent is that planned, lighter cleans preserve coatings better and cost less over the life of the building than occasional heavy interventions after years of neglect.
The economics are straightforward. Removing light soiling is a wash. Removing established lichen from a degraded coating is a restoration job, and once the coating has actually failed the only remaining options are overpainting the envelope or replacing panels, both of which are an order of magnitude more expensive than maintenance.
If a building has never been cleaned, the useful first step is not a quote. It is an assessment of what condition the coating is genuinely in, because that determines whether the job ahead is cleaning or restoration.
Common Questions
Will cleaning damage the cladding?
Not if the method matches the panel and coating. Damage comes from excessive pressure, aggressive chemistry, or cleaning a coating that has already failed. Establishing panel type and coating condition before starting is what prevents it.
Can cladding be cleaned while the site stays open?
In most cases yes. Work is usually phased elevation by elevation, and where an area cannot be taken out of use during the day it is scheduled out of hours or at weekends.
Does cleaning restore faded colour?
It restores colour that is hidden under soiling. It cannot restore pigment lost to UV degradation. If a panel is genuinely faded rather than dirty, cleaning will improve uniformity but the underlying fade will remain, and coating is the next option.
How long does an industrial unit take?
It depends far more on access and elevation area than on floor area. Access method, working height and whether the site stays operational are the factors that move the programme most.
