Avoiding common roof specification risks

Martin Fisher, Technical Manager at IKO outlines the main ‘high-risk’ areas that need to be considered when producing a roofing specification to ensure legal compliance and the avoidance of costly remedial works.

Getting the specification right on any roofing project is of paramount importance. If it is not absolutely right at the start then the responsibility for the required remediation work falls to the person who undertook the specification.

Mistakes made in a specification can be very costly, and sometimes the penalty can be far greater than just financial, especially when it comes to safety. It can be difficult to ensure you have accounted for everything but these are the aspects that cannot be overlooked.

Health and Safety

Often the butt of jokes, ‘elf and safety’ is no laughing matter when it comes to roofing projects. Safe working practices for the specific project and its individual circumstances need to be written into the specification right from the start.  It’s a legal requirement to protect the health and safety of every individual working on a construction project and is especially important with roofing projects. This must always be treated as the number one priority.

Falls and Drainage

Failing to accurately calculate drainage calculations at the specification stage can lead to water pooling and eventually roof failure. This is especially important on projects with large areas of flat roofing such as schools, hospitals and care homes where the consequences can be very serious.

Fall calculations must consider the entire roof specification, not just the gradient. The correct gradient will achieve successful run-off but the specification must also consider the direction of the falls and where excess water will flow to ensure the water runoff is directed to the location of the drainage points.

Thermal Performance

All new buildings and large-scale refurbishment projects must meet the thermal requirements of Approved Document Part L of the Building Regulations. Care must be taken to specify appropriate insulation in order to avoid thermal bridging at the wall/roof junction, which can in turn lead to condensation and damp. Immediate remediation works may need to be carried out if the roof fails Building Control inspection, adding extra time and costs to the project.

Sills and Thresholds

These details are a common design challenge in older buildings.  If a roof is being refurbished and additional insulation is required, then the resulting increase in the height of the roof may require window and door thresholds to be raised too.

The newly raised height of the building may mean that a fascia board is required in order to protect the perimeter edges of the roof system. It is far easier to check this at the specification stage rather than having to go back and correct it later.

Edge Protection

Perimeter systems that strike the right balance between safety and access to the roof are essential. If a roof needs regular maintenance, or if it has plant on it that will itself need maintenance, then edge protection to protect workers from falls is required.  A safe and secure route to gain access to the roof should be designed for maintenance workers.

Rooflights and Glazing

Specifications must consider existing rooflights, particularly on older buildings. These buildings may not be as safe as they appear and glass should never be assumed to be weight bearing and considered fragile. Replacing rooflights, or even simply moving around on a roof which has an opening, needs to be carefully planned to avoid the risk of falls.

Depending on the usage of the building, it is possible for rooflights to cause condensation. If access to the roof is achieved with or without the building owners’ consent to try and remedy this, if some were to fall through, prosecution could follow swiftly.

Roof condition and refurbishment

As with existing rooflights, when carrying out the refurbishment of a roof, the roof deck must never be assumed to be weight bearing. Always check the deck of a roof before setting foot on it. A detailed analysis of the roof condition may alternatively reveal areas of the existing roof structure that can be salvaged to avoid unnecessary costs.

Guarantee Term

Finally, check the guarantees of all products and systems you are planning to use. Guarantees vary in length and complexity: it is extremely important to be very clear as to what cover you or your client requires and that it matches the length of the building’s expected lifespan.

Failure to pay enough attention to the guarantee terms may mean that you end up with a guarantee that covers the roof for less years than you need, that does not cover all the eventualities you expect or that the installation does not comply to the guarantee procedures and therefore the guarantee is null and void.

It is important to be aware that these areas of risk are not exhaustive; there may be other hidden dangers that can only be discovered by a full and thorough analysis of the roof. However, these are the most common reasons why roof specifications fail. Working with the right people will ensure a correct specification is produced at the outset, avoiding expensive remedial measures or legal action – and hopefully a happy client!