Two quotes for the same roof cleaning land on the table. One is half the price of the other. The first reflex is to look for where the difference in margin is hiding. Most of the time, it is hiding nowhere: the two companies are simply not offering the same service. One covers the roof alone, the other the roof and facades. One applies a biocide diluted to the minimum, the other at the dose on the technical data sheet. One has included the flight authorisation and the safety perimeter, the other has not. One provides a residual treatment, the other a simple bleaching. A drone cleaning quote can only be compared once both offers are put on the same scope.
Comparing drone cleaning quotes means, first of all, bringing two offers back to the same scope. This article proposes a method and a grid for doing so, recalls the information the law requires, and flags the elements that should raise concern.
Cleaning quotes: what the regulations require
In France, breakdown, repair and maintenance services in the building sector are subject to price information rules. The order of 24 January 2017 (in French), a French ministerial regulation, notably requires a detailed quote to be provided before work is carried out above a certain amount, or at the customer’s request. This quote must include, among other things, the date, the name and address of the company, the detailed breakdown of each service and product by quantity and unit price, travel costs where applicable, and the total amount excluding and including taxes.
The VAT rate also deserves checking. For maintenance work on dwellings completed more than two years ago, the intermediate rate of 10% may apply under certain conditions, instead of the standard rate of 20%. The detailed rules are set out on impots.gouv.fr (in French), the French tax administration’s website, and in the official tax documentation (in French). Two quotes that are identical excluding tax can therefore show a gap of nearly 10% including tax if one applies the wrong rate. For commercial buildings, the standard rate applies.
These rules set a minimum of transparency. They do not guarantee that two quotes are comparable.
The eight items of a drone cleaning quote
A complete quote breaks down into eight items. They do not always appear as separate lines, but each must be covered, either explicitly or by a clear statement.
1. The scope: surfaces and substrates
The quote must detail each surface treated, with its approximate area and its substrate: clay tile roof, north facade in render, gable in cladding. It must state what is excluded, such as balconies, joinery, gutters or outbuildings. A quote that merely says ‘roof and facade cleaning, 250 m²’ allows no comparison. Our article on roof cleaning by material explains why identifying the substrate determines everything else.
2. The preliminary survey
An inspection flight or site visit before the quote makes it possible to spot the defects that make cleaning a bad idea: broken tiles, cracked render, failed joints. Some companies include it free of charge, others charge for it, and others skip it and price from satellite images. For a fibre cement roof dating from before 1997, the asbestos survey is a mandatory prerequisite, which must appear on the quote or be explicitly excluded with a statement of who is responsible for it.
3. The product, the dilution and the consumption
The trade name of the product, its active substance, its dilution and the planned quantity per square metre must appear on the quote or in an appendix. This is the item where price differences are easiest to manufacture: halving the concentration halves the cost of the product, but also reduces the effectiveness and the duration of the effect. Compare the proposed dilution with the one on the manufacturer’s technical data sheet. A serious data sheet states the compatible substrates, the application method and the dilution: the one for SCALP ANTI-M, for example, specifies that it is used ready to use, without rinsing, and that it can be sprayed by drone. A product presented as ‘ready to use’ should not be diluted by the company.
Use biocides safely. Always read the label and product information before use.
4. The application method and rinsing
Application alone, application followed by rinsing, prior mechanical removal of moss cushions: these are not the same services. A quote that promises an immediately visible result with a residual biocide should raise concern, because the two are rarely compatible. Our comparison hypochlorite or quaternary ammonium explains why.
5. The finishing treatment
A residual anti-moss treatment or a water repellent is sometimes included, sometimes offered as an option, sometimes omitted. It often represents a significant share of the price. Our article on water-repellent and anti-moss treatments helps judge whether it is worth its price.
6. Aviation compliance
Site visit, risk assessment, operational authorisation, airspace check, local permits for occupying the public highway: these costs are largely fixed. Our article on drone regulations estimates that they generally represent 0.1–0.3× the reference unit, one drone cleaning pass on a reference house. A quote that makes no mention of them may mean that the company holds a standing authorisation whose cost it spreads, or that this work has been skipped.
7. Protection of surroundings and water
Safety perimeter, protection of vehicles and plants, blocking of downpipes and road gullies, management of collected water. These measures have a modest but real cost, detailed in our article on runoff water.
8. Conditions: weather, acceptance, guarantees
What happens if the weather prevents the work on the scheduled day? When and how is the result assessed? Is there a commitment on the duration of the effect, and on what conditions? These clauses cannot be priced, but they often make the difference in the event of a dispute.
The comparison grid
To bring two quotes back to the same scope, fill in a grid like this one. Each line must receive a precise answer, or the entry ‘not specified’, which is itself a piece of information.
| Item | Quote A | Quote B |
|---|---|---|
| Surfaces treated and substrates identified | ||
| Explicit exclusions | ||
| Preliminary survey or inspection | ||
| Product, active substance and dilution | ||
| Application method and rinsing | ||
| Finishing treatment included or optional | ||
| Operational authorisation and site plan | ||
| Protection of surroundings and water | ||
| Postponement in case of bad weather | ||
| Acceptance criterion and date | ||
| Insurance certificate attached | ||
| VAT rate applied |
Once the grid is filled in, adjust the amounts. If quote A includes a residual treatment that quote B offers as an option, add the option to quote B. If quote B covers four facades and quote A two, scale the amounts to the common surfaces. You will often get a much smaller gap than at first glance, and sometimes a reversed one.
An example: two quotes brought back to the same scope
Let us take a common case. A detached house, with a 140 m² concrete tile roof and 180 m² of rendered facades, receives two quotes. The amounts are expressed in the reference unit used in our articles.
Quote A shows 0.8×. It covers the roof and the north and west facades, with an ‘anti-moss treatment’ whose product is not named. It mentions neither flight authorisation, nor protection of the surroundings, nor finishing treatment.
Quote B shows 1.4×. It covers the roof and all four facades, names a quaternary ammonium-based biocide at the dilution on the technical data sheet, includes a residual treatment on the roof and the diversion of the two downpipes connected to the stormwater system, and attaches the operational authorisation.
At first sight, the gap is 75%. Let us bring the two back to the same scope:
- South and east facades, missing from quote A: adding them pro rata to the surface areas, quote A rises to about 1.0×.
- Residual treatment, missing from quote A: company A offers it as an option at 0.25×, bringing its total to 1.25×.
- Protection of downpipes and surroundings: company A, when asked, adds it for 0.05×. Total: 1.3×.
- Dilution: quote A applies half the recommended concentration. Nothing guarantees that the effect will last as long.
The real gap is no longer 75% but less than 10%, and the cheaper quote is still the one whose product is under-dosed and whose aviation compliance is not documented. This scenario is constructed for the example, but its logic is found in most real comparisons.
Clauses to add to the contract
An accepted quote constitutes a contract. Before signing it, it is useful to have a few points specified in writing that do not always appear in standard templates:
- the acceptance date for the result, set several weeks after the work for a biocide treatment, since dead biomass takes time to disappear,
- the acceptance criterion, for example the absence of visible regrowth on the treated surfaces at a given date, established from photos taken from the same viewpoints,
- the procedure in the event of damage, with the company’s commitment to report the claim to its insurer within a given period,
- the handover of the images documenting the condition before and after the work.
Orders of magnitude to place a quote
The following ranges, expressed in the reference unit used in our articles, help spot an abnormally low or high quote. They are indicative and vary by region, access and the condition of the building.
| Service | Indicative cost (× reference unit) |
|---|---|
| Reference house, roof and facades | 1.0 |
| Reference house, roof only | 0.5–0.7× |
| Residual or water-repellent treatment as an extra | 0.3–0.6× of the cleaning |
| 5-storey building, roof and facades | 4–7× |
| Fixed compliance costs | 0.1–0.3× |
A quote well below these ranges is not necessarily suspicious, but it calls for a simple question: what is missing from it? A quote well above them may reflect real constraints, such as a difficult site, complex water management or an asbestos roof.
Warning signs
Certain elements should give you pause before signing.
No authorisation document available. A company operating legally in the Specific category holds its authorisation or its declaration, and can provide the reference within minutes. Our article on European drone regulations explains why no spraying flight can fall within the Open category.
No insurance certificate covering spraying. The certificate must mention aerial work by drone and spraying, and must not exclude damage to the property being treated. Our article on drone insurance details the points to check.
An unnamed product. ‘Professional anti-moss treatment’ is not a product name. Without a reference, it is impossible to check the authorisation, the compatibility with the substrate or the environmental precautions.
An unconditional promise of duration. A ‘10 years moss-free’ guarantee does not take account of exposure, climate and biology. Our article on facade moss removal explains where duration figures come from and what they really measure.
A large deposit before any work. A reasonable deposit is common, but near-full payment before the job, especially for a service whose result is gradual, leaves little recourse.
High-pressure canvassing. Moss removal offers made through cold calling or door-to-door selling are regularly the subject of warnings from consumer associations. For a contract concluded off-premises, the consumer in principle has a withdrawal period, and no payment can be demanded before a period of seven days has expired, except in the cases provided for by the French Consumer Code.
Beyond price: three questions that decide
When two quotes are comparable and close in price, three questions often settle the matter.
Who actually flies? If the signatory company subcontracts the aerial part, the relevant authorisation and insurance are those of the subcontractor. Ask for its name and its documents.
How is the initial condition documented? A company that films the roof and facades before the work and gives you these images protects you as much as it protects itself.
What happens afterwards? A follow-up after a few months, a check that dead biomass has been removed, advice on gutters that need clearing: these services cost the company almost nothing and often reveal how it works.
Drone cleaning quote: the essentials
A drone cleaning quote is compared item by item, not on the total amount. Bring the two offers back to the same scope, check the dilutions, the finishing treatments, the compliance costs and the protection of the surroundings, and check the VAT rate. The cheapest quote is often not the cheapest for the same service, and the most expensive is not always the most complete. For a copropriété, the French system of co-ownership of a building, this rigorous comparison is also what allows a quote to pass the vote at the general meeting.
