Drone surveys are fast becoming a highly sought after method for building condition surveys. And rightly so! They are found in an array of different sectors and range from beginner level to extremely advanced capabilities. Not only are they versatile, extremely cost effective and efficient, they also offer zero carbon footprint.
This case study is in no way intended to invalidate the benefits of drone surveys or deter anyone from using them (after all, SAT utilize drones as part of our inspection services), but rather to illustrate that drones do have their drawbacks. Something that must be taken into account when choosing them for inspections. Specifically the type of inspection required.
A Bit About Drone Surveys
The use of drone technology for undertaking drone surveys is not new, in fact it can be traced as far back as the 1950’s, with typical uses being drone mapping within the military and defence sectors. However, as technology progressed, so have the drones and with that their operational capacities.
Including some pretty advanced Ultra 4K recording capabilities, thermal imaging features, detection systems and audio recording (to name a few). However, they do lack one thing. Hands! Afterall, a drone is a UAV (unmanned aerial vehicle), so therein lies the difference. Let us explain a little more.
No Hands! Is This Really an Issue?
In a nutshell no. However, the difference is important when it comes to the requirements of the drone survey and the subsequent reportable information expected. Depending on the requirements, it is important to note that if you are looking for a structural/building condition survey, then utilizing a drone as a means of inspection is only ever going to be visual in nature.
With older buildings, such as listed ones, where stonework deterioration is a high probability, then consideration should be given to physical checks as part of the inspection.
Of course, a drone survey can be accompanied by a physical inspection. But this would incur additional costs, as two surveys are being conducted. Something that should be taken into consideration.
Referencing Standards
In an online publication by RICS on Tenement Maintenance Working Group: Inspections Sub-Group, they touch on the British Standard Survey (BS7913:2013, B5 Inspection Reports).
The “Scheme Property” as defined in the Tenements (Scotland) Act 2004, covers all areas that require inspection. British Standard (BS7913:2013, B5 Inspection Reports) was deemed as adequate in covering all these areas under this Act.
Below is an extract from one of the lists of specifics pertaining to Roofs:
“The roof has to be inspected through physical/clear sight of full roof. Drones, at present, are problematical”
So is a Physical Inspection Better?
This would really come down to the type of inspection required. With physical inspections being significantly more thorough, they don’t always have to be used for all inspections/surveys.
General surveys, where an overall understanding of the property/building is required, then undertaking a drone survey would be more beneficial.
Perhaps key areas need to be surveyed on a building where conventional access (without specialist requirements) is not possible, then drones would be the preferable option.
But if there is a possibility of loose material or defective sections that require closer checks, then physical inspections should be considered as a preferred option.
Drone Surveys vs Physical Inspections
Determining Factor
Setup Requirements
Inspection Duration
Inspection Capabilities
Exclusion Zone Requirements
Simultaneous Operations
Budget & Costing
Drones (UAV)
30 - 45mins
20-30mins flight time
Visual and Thermographic Cameras
30m radius from drone
Increased risks with multiple UAV deployments
More cost effective
Rope Access
1 hour
7 hours
Visual | Physical | Thermographic | Endoscopic
Around 5m radius
Only limited to number of anchor points
Dependent on technician requirements
The Importance of this Drone Survey Case Study
As an inspection and maintenance company, we feel it is important to highlight the key differences between drone surveys and physical inspections and how they can and should work in tandem with one another.
We remain steadfast in our approach to 100% transparency with our clients and always ensure our recommendations are in line with their individual requirements. Therefore providing them with real life examples of these key differences allows them to make informed decisions regarding their building condition survey requirements.
So let’s take a closer look at the project and what the initial requirements were from the client.
About The Building Repair Project
The property is an A listed tenement building in Edinburgh. The client (a property owner within the building) had requested and sourced a company to undertake a building condition survey on the property. This survey was conducted via drone, with an accompanying condition survey report submitted afterwards.
As a result of this survey and the subsequent observations identified within the report, Specialist Access Technicians were requested to provide a quote to undertake the repairs to certain items within the report that were of the highest priority.
The observations were graded with a “traffic light” system for levels of priority. The priority levels were as follows:
- Red – Intervention within 0-12 months
- Yellow – Intervention within 1-2 years
- Green – Intervention within 3-5 years
Overall, there were 245 observations/recommendations listed in the survey report. SAT however, were only tasked with closing out the red and yellow items that required work at height methods. In total, SAT closed out 63 items which was the majority of the “red” items, as well as a number of “yellow” items.
Examples of Observations That Required Further Intervention
Below are some examples of observations identified during the drone survey that SAT were requested to quote on rectifying. While the initial observations were correct, only once the technicians were up close, did they observe further associated observations.
Example 1 - Defective Cornice Stone
An extract from the survey report. “Failed stone cornice – deterioration to bottom edge causing falling masonry. Replacement cornice section required”. This was accurate, however it was not just the one section that was defective.
Once the technicians were underside the stone cornice, they observed the deterioration was present on the cornice sections either side of the affected one. Cracks and missing pieces were also observed on sections to the left.
Example 2 - Fractured Stone
In this example the observation was a fractured stone, with a yellow priority rating. There are instances in which fractured stone can be rebuilt in situ, therefore as the rating was intermediate, it appeared a localised repair would be possible.
However, once the technicians were in front of the affected stone, the observed the stone was cracked right down the height.
Extract from the survey report. “Fractured stone evident. Potential for water ingress which will cause further deterioration of stone”. This is an accurate assessment from the field of view of the drone. However, when it comes to costing off the report itself, it is open to interpretation.
The technicians positioned themselves in front of the stone to assess the condition and found the stone was cracked right through and down into the underlying stone. Additionally, the section to the left of the crack had shifted towards the inside of the property.
Example 3 - Defective Gutter
In this example, the drone observed a missing gutter stop end with a red priority rating. Based off the report itself, this repair would have been quick with extremely low material cost. The stop end was purchased before hand and the technicians proceeded to install the missing piece.
It was only once the technicians touched the gutter itself, did the more pertinent defect become apparent. The problem didn’t just lie with the missing stop end, but the entire gutter configuration itself.
The drone identified three different observations in this photo.
- Poor decoration to top section of cast rainwater pipe
- Missing stop end to cast gutter
- Gutter filled with debris (lower gutter section)
The missing stop end was labelled with a red priority rating, while the others were labelled green. Therefore SAT were requested to only close out the stop end.
When the technicians were in position in front of the gutter, they observed the gutter had sagged away from the downpipe outlet. This was due to missing and defective hangers. As the picture of the gutter end illustrates, the original stop end had cracked, with the majority of it falling down. Significant movement was also occurring on the gutter itself due to the defective fastenings.
Additionally the cast itself had deteriorated to a point where any attempt to remove the corroded stop end fastening bolt, would result in the cast itself cracking due to how brittle it had got.
Due to the additional observations identified once the work had begun, this resulted in a new gutters and hangers being installed. What would of been a simple stop end installation, turned into a full replacement.
Example 4 - Missed Window Sills
In this example, there are two cracked window sills on two different levels that were not identified during the drone survey. There could be varying factors as to why they were missed, but it does highlight the difference with being up close to the building as opposed to from a distance.
Typically with physical inspections (by utilizing Rope Access), the technician is right against the property. Therefore making it easier to identify any observations that require rectification.
In this case, SAT were not undertaking any work at these two levels, but rather just underside the stone cornice at the top. Whilst the technician was slowly descending (checking the building during descent), the cracked window sills were observed.
Project Costing and Planning After Drone Surveys
Accurate costing of projects is not only beneficial to a business, but to the consumer as well. It should always be a priority and having the necessary information to make informed calculations is crucial.
Naturally there are unforeseen costs associated with various works, so processes will be in place to account for this. There is no way to clearly define all costs associated with repairs to historical buildings for example. Given the age, it can not be guaranteed that underlying areas will be acceptable.
However, the majority of costs associated with repairs to a property after a building condition survey can be taken into account if everything has been thoroughly checked.
The Missing Gutter Stop End
Taking this example, the costs of this could have been mitigated. For the project, the stop end was the only item that required rectification pertaining to the rainwater system. Therefore, SAT had sourced the piece, collected it and brought it to site.
Once the work had begun, and the technicians observed the actual issues with the gutter, further materials had to be sourced. This meant going back to the supplier to collect the remaining materials. These additional costs incurred will inevitably fall back onto the client.
While this example may appear insignificant, it does illustrate how easily costing can be overlooked without the correct information.
Conclusion
To summarize this drone survey case study, it is clear drones do have their advantages in terms of cost, time and resources. They are more agile and can quickly access normally inaccessible areas.
However, when it comes to building condition surveys for instance, they do have their limitations in regards to levels of detail. Something that should be taken into account when thinking of having such a survey conducted.
Especially on listed buildings, where the stonework is old and potentially deteriorated. In cases such as these, the risk of loose stonework and rendering is much higher. A drone will not be able to determine whether something is loose. Unless of course it is painfully obvious, such as the stone has shifted and no longer in its intended position.
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SAT are the leading Building Maintenance and Inspection company in Edinburgh. We offer our clients cost effective solutions to their work at height requirements. Our ability to complete demanding projects on time and within budget, is something we are proud of. It is our mission to support our clients in all aspects of their building maintenance, servicing and inspection requirements. 
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