The short answer: A good commercial window cleaning specification removes guesswork by defining exactly what’s included, so every contractor prices the same job and you can compare bids fairly. It should cover the full scope of works, cleaning frequency, the access methods to be used (water-fed pole, rope access, cradle or BMU, and MEWP), all safety and compliance requirements, and the reporting standard you expect. A vague spec is how FMs end up “paying more and getting less”, because they compared prices that were never for the same thing.
Here’s a scenario every facilities manager and managing agent knows. You put your window cleaning out to tender, three quotes come back, and one is noticeably cheaper than the others. It looks like the obvious choice, so it wins.
Six months later you’re chasing missed cleans, fielding resident complaints, and realising the cheaper quote quietly left out half of what you assumed was included. The saving has vanished, and then some.
We call this the tender trap, and it’s rarely the FM’s fault. It happens because of one thing, a specification that wasn’t tight enough to compare bids properly. When the spec is vague, contractors are free to interpret it however keeps their number low, and you end up comparing prices that were never for the same job.
The good news is that a clear specification fixes this completely, and writing one is more straightforward than it looks.
Why a cheap tender usually costs more
A low quote isn’t automatically a bad one, but on a vague spec it almost always hides gaps. Maybe the frequency is lower than you expected, maybe the internal atrium glass isn’t included, maybe the safety testing has been assumed rather than priced, maybe the reporting simply doesn’t exist.
None of that shows up on the quote. It shows up later, as extra costs, missed work, and workload landing back on your desk. So the cheapest number on paper frequently becomes the most expensive relationship in practice, which is the opposite of the value for money you were trying to protect for your residents and the service charge.
What a vague specification actually does to your comparison
The whole point of a tender is to compare like for like. A weak spec destroys that before you’ve started, because every contractor is effectively quoting for a slightly different job.
One prices four cleans a year, another prices two. One includes the difficult atrium access, another skips it. One builds in anchor testing and reporting, another leaves it out to sharpen the price. You’re no longer comparing suppliers, you’re comparing assumptions, and the lowest assumption usually wins for the wrong reasons.
Tighten the spec, and suddenly the comparison becomes honest. Everyone’s pricing the same scope, and the differences between bids tell you something real.
What a proper window cleaning specification should include
You don’t need to be technical to write a strong spec, you just need to be clear on each of these areas.
Scope of works. Exactly which glass and surfaces are included, external and internal, along with any atria, balconies, cladding, or solar panels. Name the exclusions too, so nothing is left to interpretation.
Frequency. How many cleans per year, and whether different areas are cleaned at different intervals. This is one of the most common places a cheap quote quietly drops below what you need.
Access methods. State the methods appropriate to your building, whether that’s water-fed pole for the lower levels, rope access for the high-rise elevations, or cradle, BMU and MEWP where they’re required. This matters because access is where cost and safety live, and it’s where corners get cut.
Safety and compliance. Require a job-specific RAMS, current anchor and mansafe certification, and evidence of competence for work at height under the Work at Height Regulations 2005. Make documentation a condition of the contract, not an afterthought.
Reporting and standards. Define the reporting you expect, ideally same-day completion reports with before-and-after photos, and set clear SLAs and KPIs for quality and response times. This is what turns a service from invisible into accountable.
Resident communication. On residential developments, specify how and when residents will be notified before each visit. It’s the single biggest lever on complaint volume, so it belongs in the spec.
Put those six areas in writing and you’ve removed almost all the wriggle room. Every bid now answers the same questions, and the contractor who was planning to win on a thin, vague number no longer can.
How to compare the bids fairly
Once the spec is tight, judge the responses on more than price. Look at how completely each contractor answered the spec, how clearly they explained their access and safety approach, and how confident they were on reporting and resident communication. A partner who engages properly with a detailed spec is showing you how they’ll run the contract. A contractor who skims it and sends a headline number is showing you that too.
The aim isn’t to pick the cheapest or the dearest, it’s to pick the one who gives you genuine confidence that the job will be done to standard, safely, and without you having to chase. That’s the difference between a contractor and a service partner, and a good specification is how you find them.
Write the spec properly once, and it protects you for the entire length of the contract.
Frequently asked questions
What should a commercial window cleaning specification include?
A strong specification covers six areas: the full scope of works and exclusions, cleaning frequency, access methods (water-fed pole, rope access, cradle/BMU, MEWP), safety and compliance requirements (RAMS, anchor and mansafe certification), reporting standards (completion reports, SLAs, KPIs), and resident communication.
Why is the cheapest window cleaning quote often more expensive?
On a vague specification, a low quote usually hides gaps, lower frequency, excluded areas, unpriced safety testing, or no reporting. Those gaps surface later as extra costs and workload, so the cheapest bid frequently becomes the most expensive contract.
How do I compare window cleaning tenders fairly?
Write a detailed specification so every contractor prices the same scope, then compare responses on completeness, clarity of access and safety approach, and reporting, not just the headline price.
How often should commercial windows be cleaned in London?
Frequency depends on the building, its exposure, and its use, but many London residential and commercial developments run between two and four external cleans a year, with internal and specialist areas often on a separate schedule. Define your required frequency in the specification.
What safety documentation should a window cleaning contractor provide?
Expect a job-specific RAMS, current anchor and mansafe certification (inspected within the last twelve months on high-rise buildings), and evidence of competence for work at height under the Work at Height Regulations 2005.
