8 Common Roof Specification Risks

Mistakes made in a specification can be very costly. If the specification is not absolutely right at the start then the remediation work required to make the roof good will be borne by the person whom undertook the specification.

Worse still, if health and safety issues have not been explored properly, then the cost could be far greater than just money.

No-one can be an expert in everything, so the key to getting a roof specification perfect is to work with the right partners whose expertise can ensure that the proposed solution is right for the roof structure, the type of building and its occupants.

In our experience, there are at least eight “high risk” areas where specifications can go badly wrong.

8 Common Roof Specification Risks

1. Construction Design and Management (CDM) Regulations 2015

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.

2. Falls and Drainage

The incorrect design of falls and drainage can lead to water pooling and, eventually, to the failure of the roof. Given the typical building design with large areas of flat roofing, schools, hospitals and care homes can be particularly vulnerable and the consequences of leaks caused by roof failure particularly serious. Drainage calculations and condensation risk analysis can help to minimise these risks pre-installation.

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.

3. Thermal Performance

All new buildings and large scale refurbishment projects must meet the thermal requirements of Approved Document L of the Building Regulations.

Incorrect or inadequate specification of insulation and incorrect detailing to avoid thermal bridging, particularly at the wall/roof junction, will lead to an under-performing roof.This can result not only in poor thermal insulation, but thermal bridging can also lead to condensation and damp. If the project is required to be signed off by the building control then these types of issues may lead to future work being required.

Thermal Performance

The thermal performance of a building is critical to meet both building regulations on new builds and refurbishments.

4. 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 also mean that a fascia board is required for the first time in order to protect the perimeter edges of the roof system.

5. Edge Protection

The combination of safety and access is a tricky balance that is achieved by specifying the right perimeter systems for the design of roof and its intended use. Both aspects must be considered.

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 will not be a “nice to have”: it will be a necessity. A safe and secure route to gain access to the roof should also be considered as part of the risk management for maintenance workers.

6. Rooflights and Glazing

Old glass rooflights are always risky as they may not be made of safety glass and should never be assumed to be weight bearing.

Roof specifications should pay particular attention to the health and safety risks associated with any hole in the roof.  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.

Rooflights may well be a requirement for a flat roof in order to get the required volume of light into the building below:  in a refurbishment project rooflights may need to be raised to accommodate additional insulation – as with sills and thresholds outlined above. 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.

7. Roof Condition and Refurbishment

Always check the deck of a roof before setting foot on it.  HSG33 provides guidance on the risk associated with working at height, so when planning the refurbishment of an existing roof, the condition must be thoroughly examined – don’t take anything for granted or assume that the existing roof is able to bear the weight of a person, plant, machinery or even of a new roofing system.

At the other end of the scale, a detailed condition review may reveal areas of the existing roof structure that can be salvaged to avoid unnecessary costs.

8. Guarantee Term

Guarantees vary in length and complexity depending on the products and system being installed: it is extremely important to be very clear as to what cover you or your client require 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.

Note: Always read the small print and be careful what you are signing as it may not be as comprehensive as you think!

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