What's on the roof?

Simple maintenance can prolong the life of roofs on educational establishments. For instance, by clearing leaves and other debris from outlets and gutters. Protective chippings (if they were present) that have been moved by wind scour should be replaced too and any loose trims or flashings refixed.

It’s also important that close consideration is paid to energy efficiency aspects of roofing and the reduction of carbon emissions, which can lead to lower running costs and a positive return on investment.

Regular inspection by a roofing contractor is paramount, as is first-class, qualified advice on a roof’s weatherproofing qualities, performance and longevity.

Understanding roof technology
Where repair and maintenance are concerned, it is essential to have an understanding of the construction and technology of our roofs. For instance, post-war built schools generally have a number of flat roof areas as opposed to traditional pitched roofs. This article primarily concerns these types.

Flat roofs are not really ‘flat’. They may be curved and have a pitch of 1 to 10 degrees, and originally have had a bituminous-based waterproofing – that’s asphalt or felt laid over a supporting deck. The deck is likely to be of concrete but could also be woodwool slabs, timber or profiled metal.

When they were built, energy efficiency was not considered too important so the inclusion of insulation would have been minimal – perhaps no more than a layer of fibreboard. Over the years the waterproof coverings may have been overlaid or replaced with another bituminous system, or with a polymeric or rubber single ply waterproofing or a GRP based liquid applied coating.

It is probable that some attempt at increasing the thermal efficiency of the roof would have been made during this time. This means that even individual flat roofs could include various waterproofing systems, build-ups and structures that may require differing approaches to close investigation and refurbishment.

Pitched roofs, that is roofs in excess of 10 degrees (usually 25 to 45) consist of a support structure of timber, steel or concrete, with the waterproof elements being tiles or, occasionally, metal sheets. A number of metal roof systems were developed post war by aircraft manufacturers, specifically for schools and consisted of flat aluminium sheets riveted to aluminum spars. This technology may still be in use though it may have received various attempts at re-waterproofing.

Common problems
There may be several common flat roof problems. One, for example, is leakage caused by the failure of the waterproof covering. This may be due to several factors such as bad design, poor detailing, bad installation and inappropriate materials. Other causes can be an inability to withstand movement, thermal shock, impact or other damage, the deterioration of seams, trims or flashings, failure of previous repairs, lack of maintenance or simply the waterproofing material reaching the end of its service life.

Ponding of rainwater can occur but is not necessarily a problem though it may be an indication of the degradation of the supporting deck due to water ingress or condensation. It may also indicate the lack of fall to the roof, which may be addressed when refurbishing. Blistering may also be present but, once again, is not problematic though it should be monitored periodically.

Pitched roof coverings can last for over 100 years. However, these roofs should be examined for loose and broken tiles, flashings and other problems. Metal sheeted roofs can be inspected for corrosion, loose or missing fixings, and trims.

Refurbishment & energy efficiency
If the roof is to be simply refurbished by recovering then the Building Regulations will come into play, particularly with regard to energy efficiency. They state that if more than 50 per cent of the existing waterproofing is being stripped, if it’s technically and economically feasible the whole roof must be brought up to the standard of the current energy related regulations. This means that a roof will require substantially more insulation than is currently present.

For example, a school roof installed in 1995 will, possibly, have about 40mm of rigid polyurethane insulation meeting the then current regulations. In 2012 that thickness will need to increase to 140mm.

When a roof is refurbished rather, than simply repaired, it may have other potential roles, in addition to ‘keeping out the weather’. For instance it may lend itself to a vegetated or ‘green roof’. Or perhaps it could be the location for important microgeneration equipment such as solar thermal or photovoltaic panels. In this case the entire roof design including the structure will need to be taken into account.

Government and local authorities are encouraging the take up of micro generation where roof areas can provide the basis for mounting solar photovoltaic collectors. The electrical energy they can produce may be used to power a building’s interior. Any extra electricity generated can be fed into the National Grid.

Many solar systems are available for retrofitting to both flat and pitched roofs. The key considerations, however, are that the roof structure is capable of accepting the increased load, that the roof members are substantial enough to take the additional mounting brackets and fixings and, of course, the waterproofing effectiveness of the roof covering is maintained.

No existing roofs were designed to take solar equipment and, therefore, expert advice will need to be obtained from a qualified engineer. While solar equipment is likely to be commissioned by a supplier it will be the roofing contractor’s responsibility to ensure its effectiveness and the roof’s integrity.

Greening your roof

Green or vegetated roofs are growing in popularity – especially in the new-build arena. In some instances they can be retro-fitted to existing roofs. The benefits of a green roof include sustainable drainage, increased bio diversity, countering of solar gain and increased thermal efficiency.

In a school a green roof can provide interest and the feeling of well-being. They are installed as a complete system comprising the waterproofing, root resistant layer, moisture retention layer, drainage layer, filter layer and, finally, the growing medium.

Green roofs are heavy – even the simplest sedum based covering adds an extra 100kg per square meter and the more intensive systems will be a tonne or more, plus the extra weight of retained rainwater. The existing roof structure must be able to accommodate significantly heavier loads.

Green roofs are highly engineered and should not be fitted and forgotten. They need careful design, maintenance and consideration for irrigation. Further information can be obtained from www.livingroofs.org

Inspecting and assessing roofs
Flat roofs are relatively easy to access for inspection, basic maintenance and to reclaim balls and other items that have been lost up there. Also, they are easy to fall off. In fact 50 per cent of fatalities in the construction industry are the result of falls from height and therefore the basic requirements of the Work at Height Regulations must be applied. This involves, even when simply inspecting a roof, that the work should be planned, supervised and carried out in a reasonably safe manner.

A trained and competent roofing contractor is totally conversant with these regulations as well as seriously regarding other potential risks, such as from asbestos-containing materials.

Competent roofer scheme brings savings
The NFRC government-approved CompetentRoofer scheme is extremely important and can bring significant cost savings to every educational establishment that needs repairs, maintenance or re-roofing work.

The CompetentRoofer scheme ensures total satisfaction, involving special self-certification by the roofing company that totally eliminates costly and time-consuming local authority building control procedures. It presents all-round cost reductions, whilst maintaining performance and legality.

Roofers’ self-certification through CompetentRoofer means that their clients get an ‘all-in-one’ service that does not need building control officer approval. The building owner receives a Building Regulations Control Completion and the roofing work is automatically registered with the relevant local authority.

CompetentRoofers receive random site inspections checks so their work is always first rate. Special training courses have been developed to increase operative awareness of the scheme and its implications. Also there is a ‘hot-line’ to anonymously report errant companies. For more information: www.competentroofer.co.uk

Special heritage roofers
Many older schools and educational establishments are listed buildings and require very special attention to detail and consideration. So the NFRC has a unique register of Heritage Roofing Contractors.

All old roofs must be covered or renewed precisely and in line with the strictest energy efficiency rules. This is because certain government parameters have been set to which roofs must comply in order to meet the common goals of zero carbon emissions. All NFRC Heritage Register roofers have the specialist knowledge, skills and workmanship to carry out this exacting work.

About the NFRC
Through its members, the National Federation of Roofing Contractors (NFRC) leads the way in possible cost-saving solutions while encouraging first class workmanship, maximum performance, plus the installation of cutting-edge materials.

For more information about the NFRC and its members see its website for more details www.nfrc.co.uk