The three measurements that decide a commercial skylight robot project are total glazing area, the tallest kerb or mullion, and the steepest pitch. Get those wrong and the machine fails on the first clean regardless of brand.
Facilities teams usually run this survey after they have chosen a supplier, which is backwards. Suppliers quote to the number you give them, so the survey determines whether the quote is real.
What should the survey measure?
| Item | How to measure | Why it matters |
|---|---|---|
| Total glazing area | Width × length per bay, sum | Decides pole vs crawler vs rail |
| Steepest pitch | Smartphone inclinometer, worst bay | Above 35° most crawlers lose grip on wet glass |
| Tallest kerb / mullion | Tape measure, across all bays | Over 30 mm stops most chassis |
| Smallest pane | Tape measure | Under 600 mm, repositioning dominates |
| Tether anchor points | Count structural points | Two anchors needed on wind-exposed roofs |
| Water source distance | Metres from nearest tap | Beyond 30 m, tank refills dominate the day |
| Power availability | Check for outdoor socket | Cable runs over 25 m need care |
| Wind exposure | Prevailing direction, adjacent buildings | Funnelling between buildings adds 20-30% |
| Access route | Door width, stair or hoist | A 40 kg case will not go up a ladder hatch |
How does pitch affect machine choice on real buildings?
Most commercial roof glazing in Europe sits between 5 and 30 degrees, which is comfortable for a suction crawler. The awkward ones are the older factory lanterns and the steep saw-tooth roofs, which regularly run 40-55 degrees.
On those, a crawler works only with a top-mounted winch and a crew that accepts slower coverage. Some projects are better served by a pole-fed brush from a walkway, even though it is low-tech. Nobody sells “keep it simple” as a product, so it rarely appears in proposals.
What does wind exposure do to the plan?
Two buildings twenty metres apart create a wind funnel above the gap. Roof edge wind speeds in that zone can run 1.5 times the local weather forecast. That changes the machine’s effective safety margin and the tether design.
Practical rule: on an exposed commercial roof, stop work at 10 m/s forecast wind, and use two anchors whenever the glazing is above occupied space. A 4 kg machine landing on a shop floor is a claim; landing on a car park is an incident report.
Does anyone actually check the anchor point?
Rarely, and it is the biggest gap in commercial skylight cleaning projects. A tether is only as good as the point you clip it to. Fixings into a purlin or a structural rail are fine; a clip around a vent pipe is not. Have the installing contractor confirm the anchor’s rated load, and get it in writing.
The same question applies to the glazing itself. A frameless bonded panel designed for 1.5 kPa snow load has not been assessed for a machine’s point loading at the edge. Ask the glazier, not the robot salesperson.
How do water and power access change the schedule?
A 20-30 litre tank covers roughly 60-90 m² on pitched glass. On a 600 m² roof, that is seven refills. If the nearest tap is 80 metres away and on a different level, refills become the day’s critical path rather than cleaning.
Two fixes: a 200-litre wheeled bowser parked on the roof (rental cost is trivial against labour savings), or deionised water delivered in IBC containers. The second also solves the spotting problem on tilted glass, where mineral residue pools at the frame edge as it dries.
What does the total first-year cost look like?
A 600 m² commercial skylight, cleaned quarterly, in a mid-wage European market.
- Manual with rope access: €9,600-19,200 per year at €4-8 per m².
- Crawler purchase: €2,500-4,000, plus €350-600 consumables in year one.
- Two-person crew time: roughly 40 hours a year across four cleans.
- Anchor installation and certification: €600-1,200 one-off.
The crawler pays back in under two years on that number, which is why the commercial case is usually clean. The domestic case is not, and that distinction gets lost when people read commercial comparisons.
Which machines are worth shortlisting?
For large shallow-framed commercial glazing, the Lingkong K3 review covers a chassis aimed at this duty cycle. For roofs where raised kerbs split the glass into bays, the Lingfeng S1 review covers obstacle crossing. Full comparisons across tested units are in the robot review archive.
One last item to put on the survey sheet: who operates it. A machine bought without a named, trained operator tends to sit in a plant room after month three. Training is a line item, not a courtesy.
Key Takeaways
- Measure glazing area, steepest pitch and tallest kerb first — those three rule machines in or out.
- Any kerb over 30 mm eliminates most suction chassis; measure across all bays, not one.
- Wind funnelling between adjacent buildings can raise roof-edge wind 50% above the forecast.
- Confirm the tether anchor’s rated load in writing before the first clean.
- Water refill distance routinely costs more hours than cleaning on large roofs.