Mending the roof of an occupied building is a balancing act between the needs of the building and the needs of those doing their jobs inside. John McMullan considers the FM's role.
20 August 2015 | By John McMullan
There are some environments where big maintenance projects can be put off until the summer recess or the annual shutdown - but for most commercial environments there is never a good time.
When it comes to roof refurbishments, however, once the existing waterproofing membrane starts to fail, replacing it as quickly as possible is both time and business-critical because water ingress can affect not only the integrity of the roof - including insulation and internal finishes - it can also damage equipment inside and disrupt normal working patterns.
It's not all bad news, though. It is possible to carry out a roof refurbishment with little disruption to the building's occupiers.
1. Assess the roof surface
In an ideal world a roof will be refurbished before the signs of wear and tear become signs of water ingress. In the real world, however, budgets, maintenance schedules and a host of other factors mean that this is not always the case.
For most occupied buildings, the decision to refurbish the roof will be taken before the existing membrane has perished to such an extent that it needs to be stripped out. If it can be cleaned and prepared to enable a roof overlay this should be the preferred option as it will prevent the noise, dust and environmental impact of a strip-out.
But if the roof is in a bad state of repair - perhaps the insulation board under the membrane has begun to deteriorate - there may be no option other than to strip out the existing system before beginning the refurbishment.
2. Select a compatible system
Where an overlay approach has been decided it's essential that the materials used, including any primers or adhesives, are compatible with the existing roof substrate. If this is not the case it could compromise the performance of the new waterproofing membrane.
If the roof surface is in a very poor state of disrepair or the chosen system is not compatible with the substrate it may be advisable to install a cover board, which will overcome any compatibility issues and create a solid and even substrate for a more robust installation.
3. Use the right fixing method
When using a single-ply waterproofing membrane, including EPDM, TPO, or PVC the membrane can either be fixed in place using an appropriate adhesive or by mechanical fixings. Often the contractor will have a preferred approach. It's essential, however, to ensure that the chosen method is compatible with the building. For example, using mechanical fixings on a concrete deck roof will require drilling, creating noise for workers inside the building. Conversely, some adhesives may create nuisance odours and solvent-free LVOC products may therefore be necessary.
4. Choose a qualified contractor
Many roof failures are down to poor workmanship, so whichever system you select it will only deliver the manufacturer's stated performance if it has been correctly installed. Check that the installation company has been approved by the manufacturer; Firestone, for instance, trains all its authorised and licensed contractors and visit installations on site to ensure that membranes are installed to the highest standards.
5. Avoid hot works if possible
Traditional bituminous roofing systems are cost-effective but involve hot works that can cause smells and present a health and safety risk because of the use of a naked flame on site, which can also result in insurance issues. While thermoplastic single-ply TPO systems involve hot-air welding, this does not require a flame; the only consideration is whether the installation team will have access to a suitable power source for the weld equipment. An EPDM single-ply system does not require either flame or a suitable power supply.
6. Avoid bad smells
Bituminous roofing systems and solvent-based resins create nuisance odours that can disturb the building's occupants. An EPDM or TPO system, on the other hand, can provide an odour-free, low VOC (volatile organic compound) solution that is ideal for schools and hospitals.
7. Keep it waterproof
To avoid the risk of leaks it's important to select a system that can be installed quickly and provide temporary waterproofing while installation is carried out. An EPDM system, for example, is installed using large sheets of single-ply membrane, which means fewer joints and faster laying so that the roof can be re-sealed more quickly. This type of system can also be used as temporary waterproofing during the project to ensure that effective 'night seal' details can be maintained during the contract period.
8. Life span and maintenance
To reduce both cost and disruption it's essential to select a system that will offer robust performance for a long time. It's also a good idea to select a system that can adapt to changes, such as the introduction of new plant on the roof. EPDM has a service life of about 50 years, is an inert material that retains its properties and may be adapted to create new details without the need for intensive preparation.
John McMullan is commercial manager of single-ply roofing specialist Firestone Building Products