Flat roofs are relatively inexpensive and very efficient to keep your buildings and your internal assets covered and protected from the weather. What can you do to identify flat roof defects?
Defects for flat roofs
Whilst their relatively low cost for a good protection plays to their advantage, this type of roof is also notorious for defects that often remain unnoticed until it is too late. As with any part of a building, they will be subject to wear and tear and will receive copious amounts of water. Regular inspection of the roof is essential to make sure that this essential element is in tip top condition and kept free of defects.
One of the most common defects is water ingress which then leads to a leak inside the building. When water ingress does occur on a flat roof, damage often goes unnoticed for considerable time as water slowly penetrates and soaks the decking, insulation and/or structure beneath. This can lead to extensive damage. If left unattended and no leak detection surveying takes place, it can weaken the whole structure and have catastrophic operational and financial consequences for you.
Other defects can occur too. You can read our most popular blog post about the five common flat roof defects here.
There are several methods of detection of flat roof defects. We have already discussed the merits of three surveying methods: ELD, Nuclear and Infrared. Here we look at core sampling.
Flat roofs core sampling to detect water ingress
Core sampling allows the surveyor to figure out how the roof was built and locate where water penetration may be. In the thermal images above you can notice a small white area that looks a little like a bowling pin. This is a small torch safely placed on a flat roof to mark the location of a core sample.
You will also note that on the left image the core sample was taken in what is showing thermally as a red area. On the right the core sample was taken in what is showing thermally as a blue area.
On the left, the red area highlights that where the core sample was taken, insulation was wet. On the right, the blue area highlights that where the core sample was taken insulation was dry.
You can find out more about the meaning of infrared colours in our Understanding Colours post.
These two images tell you everything you need to know about the accuracy of core samples. By relying solely on core sampling, your surveyor could mistakenly concludes that the entire roof needs replaced or on the opposite, that the roof is sound. How can you know for sure?
If your surveyor is employed by a roofing company, the impartiality of the advice could well be put into question. It is a matter of trust and reputation.
Flat roofs core sampling technique
The method and process of core sampling is therefore important. The core sample technique should be as follows:
- take one core sample at a high point,
- take one core sample at a low point and
- take one core sample mid-way.
Critically this should be at random locations on the roof, not in a straight line. That way the surveyor can find out if water is coming in at parapets and tracking it down, if the area around the outlet is wet as water loves gravity and then try to ascertain the extent of the damage at the mid-point.
The surveyor will take appropriate notes and photographs. Then of course, they must patch the core sampling holes by resiting the sample and sealing the edges. Often this is made using blow torches.
This technique carries high risks for you and for the surveyor:
For you risk of fire from blow torches. Smouldering the flat roof away and causing extensive damage which could cripple your business,
Again for you invalidating roof construction guarantees by cutting holes through potentially perfect waterproofing.
For the surveyor, the risks are inherent to health and safety: slipping on a wet surface, working at height, stand alone working, fire protection, etc.
It is therefore easy to conclude that core sampling should be a last resort surveying technique, just before the nuclear surveying method.
Flat roof defects: infrared is the detection solution
If you are an asset manager, estate manager, building surveyor and are being asked to make a budget go as far as possible, then it is essential you get and give impartial advice to the building owner. By investing in an infrared thermographic (IRT) survey, you mitigate risk from a third party advising whichever solution meets their commercial needs and wants.
Infrared can’t tell the difference between polyurethane and fibreboard. Wet is wet and that effects the temperature on the surface. Why? Simply put, wet insulation doesn’t insulate as well as dry insulation – so heat escapes the fabric. Also because water has a high emissivity. This means that water radiates its energy particularly well when it has finished absorbing it from the sun and from the building itself. This high emissivity makes the wet area appear warm to the infrared thermal camera.
With drones now extensively used to take the thermal pictures, thus eliminating most if not all health and safety risks for the surveyor as well as improving the accuracy of the surveying results, there is little not to like about infrared.
IRT may help you save hundreds of thousands of pounds by turning what you had assumed would be a complete “strip and re-new” into a partial strip and overlay. Conversely however the opposite may be true.
The point being: you will get the truth and if you are interested in delivering value to your clients and managing a sustainable portfolio, that’s an invaluable weapon in your armoury.
Core samples have their place of course. We will always advise you hand your infrared survey reports to your roofing company who may then core and confirm the infrared survey findings. More importantly the core sampling will allow them to establish what the roof is actually made of so that they can propose the appropriate solution for your roof refurbishment.
Do you own or manage buildings with flat roofs? We would like to know what surveying method you favour and why. Drop us a line, give us a call, let’s talk all things flat roof surveying.