At its most basic, the role of roofing and enveloping is to protect the integrity of the building. Waterproofing systems keep the internal structure protected for decades to come through all sorts of weather conditions. The materials and fastenings chosen depend on multiple factors including budget and quality, but wind load calculation should also feature high on the list of priorities for every building project and roofing contract.
Wind calculation software has made life easier for wind loading and roofing design. The software is designed to make the calculations for simple rectangular buildings. In reality, few buildings are as boxy as the software anticipates. To compute the wind load system accurately, engineers take multiple factors into account. These include the building’s location, surrounding or attached buildings, roof structure, upstands and parapets as well as antennas and any other protrusions. Therefore, there will always be a human factor involved in calculating the requirements.
Wind load calculation: the basics
The basics of wind calculation include the positive force from the wind on the facing wall, the suction on the side and rear walls, and the uplift on the roof. Other factors such as the roughness of the terrain around the building, and positive internal pressure from inside the building are important too. The highest wind load will be at the corner zones of the building where wind creates the highest turbulences. High rise buildings can create higher wind speeds on the surrounding lower buildings, therefore, wind load calculation for buildings in the neighbourhood of high rise buildings are an important part of the design process.
National and International standards
Each country has national standards to implement, which differ slightly throughout Europe. These are calculated based on peak wind speed over a statistically significant period. For example in Belgium the highest wind speed is 25 years or in Ireland is 50 years. Experienced wind calculation engineers sometimes have to make assumptions where detailed data is not available. For particularly challenging designs they may even build a scale model and test its performance in a wind tunnel. However, for the most part, engineers can easily advise on wind loads for a wide range of materials without having to create and test models.
Why guess when you can get expert advice?
Johan Pastuer, one of Soprema’s wind calculation consultants, laments the fact that not every roofing contractor takes advantage of this expert service. All too often roofing contractors only seek wind calculations when using mechanical fasteners rather than glue. This means that they may find out the hard way that the ballast they have used is not enough to withstand high wind speeds. In high wind speeds, even deep layers of gravel can be blown into one corner of the roof, particularly on buildings higher than one storey.
While wind calculation formulas may be complicated, for the contractor it does not need to be. Usually, all the roofing contractor or architect needs to do is return a completed checklist to Soprema. This provides - together with the necessary plans - enough information to carry out all of the calculations.
The familiar carpentry saying, “measure twice, cut once,” also applies to wind load calculations and building enveloping. With expert advice on wind design readily available from Soprema, we recommend that contractors seek it out at the start of a build rather than dealing with the repercussions of unanticipated wind damage at a later date. So while you should always have a wind load calculation for your projects, you don’t need to do the maths. Leave it to the experts and remove the guesswork for your next building project.
Always take into account that it is not the task or responsibility of the manufacturer of the waterproofing materials to perform windload calculations. Those calculations always have to be checked and approved by the responsible designer of the project.
Contact our team of specialists for more information and see how we can support your next project.