SIG Design & Technology looks at the importance of getting an accurate picture of the state of a flat roof before carrying out repairs. A good survey will help inform a detailed maintenance, repair and reroofing strategy.
We shall illustrate the article with examples from a primary school in the North of England. We have been working with this particular academy school for over three years, implementing an ongoing strategy to look after their flat roofs. We were originally contacted by one of our partner surveyors to take a look. Several of the flat roofs were leaking and the surveyor needed some expert help to identify the causes.
The work we have managed has been arranged in several phases, discussed in consultation with the school team to enable the school to continue to operate whilst considerable works could be carried out. Funding applications have been carried out for each phase. Phase 1 of the work, which was completed last year, allowed classes to be decanted into repaired areas in preparation for Phase 2, which has just received Condition Improvement Fund (CIF) for 2019-20.
Core Samples for School Roof Repairs
Four core samples were taken during a detailed survey in preparation for Phase 2 of the works. Three were taken from one roof area and one from a second roof. Both roofs were part of the successful CIF funding bid for this work.
What is a Core Sample?
“Taking a core sample” is the process of cutting out a small section of the roof to expose the different layers back to the deck – that is, the timber (wood) or metal surface which supports the roof insulation and waterproofing elements.
Taking a core sample allows us to check what the roof is made of, check for moisture in the construction and inspect the deck and other layers for any faults or alterations. A surveyor will take several core samples across your roofs, in areas which will indicate in his or her experience, the state of the roof as a whole.
After the core is taken out and inspected, the materials are placed back in the hole and the roof finish repaired with a patch of the correct roofing material to seal the hole.
SIG Design & Technology took four core samples. The school was experiencing leaking under each of these areas.
Core Sample 1
The first core sample showed that the roof was a bitumen flat roof laid over insulation onto a chipboard deck. There was a Vapour Control layer however the insulation was saturated and visible water within the roofing system. The chipboard deck was exposed at the bottom, but it appeared to be unaffected by the moisture at this point.
Core Sample 2
The second sample was taken from the same roof but in a different position and showed visible water and saturated insulation, and the deck here is also dry.
Core Sample 3
The third core sample was taken on the same roof but in a different place. The sample showed a complete deck failure – a chipboard deck in this area had completely rotted away and you could see a hole at the bottom of the core sample. The only thing keeping the roof in the air is a wing and a prayer! Quite a sobering thought.
Core Sample 4
The fourth core sample was taken in another roof area, a Single Ply roof membrane over insulation and a plywood deck. Everything here was dry and the deck in good condition. However, there was no Vapour Control Layer in the build up. Whilst water was displaying inside the school in this area, this water was caused by Interstitial Condensation, not by a leak – not all water ingress is caused by leaking roof membranes.
Planning School Roof Repairs
The core samples revealed areas of saturated insulation, areas of failed deck and a single ply roof without a vapour control layer. Carrying out a good number of core samples has made it possible to budget accurately for the school roof repairs in this phase. If we had only cut one or two core samples which showed the deck was unaffected, we may not have allowed for any deck replacement in the budget.
The core samples we took led us to estimate 75% deck had failed. As a result our budget and the successful school funding application allowed for all roofs to be stripped back to deck and a 75% deck replacement.
If we hadn’t made this informed calculation and the bid was successful, the school would have had to find funds from elsewhere to replace any failed deck, or even make a new grant application. The cost a new deck over this whole roof would have been over £20,000.
Our advice about intrusive surveys for school roof repairs
In order to make an accurate application for funding and for a successful project to follow we recommend that a school takes the following steps:
- Use a specialist roofing design company to make the survey and Ensure the surveyor looks at the whole roof, not just one small section. Make sure their proposal includes for the time required.
- Have your surveyor carry out sufficient core samples and inspections to gain an accurate view of the condition of the roof, not just its saturation level. Remember core samples should not be taken if the roof is under warranty.
- Ensure that a specialist roofing contractor carries out the repair and replacement works and that these are inspected by the design team who carried out the survey and made the application.
SIG Design and Technology provide our school roof repairs surveys, advice and support for free to schools and multi academy trusts. Find out more about our free roof survey and what it entails, or get in touch to discuss your project
