Avoiding Ponding Water on Industrial Flat Roofs
If you have a warehouse management position in any area within the Cotswolds, there is a chance your building was constructed with a flat roof. Flat roofs have the advantage of saving money during installation and allow for additional storage space due to the increase in height. With flat roofing, there is a trade-off. Unlike most sloped roofs, flat roofing has a tendency to collect and retain water. If flat roofs are not designed and built to drain, water can cause damage to the roof and the structure itself. It can also cause costly downtime.
What Causes Ponding Water?
Ponding is the accumulation of rainwater that is present on the roof surface due to poor drainage after a rain event. Ponding occurs to some extent on all flat roofs. However, significant, deep or widespread ponding indicates a design issue or defect in your roof. These issues may include a poorly designed roof deck with reversed slopes or insufficient grading of the roof deck to drain water, obstructed drain outlets or drain outlets that are too small, a sagging roof membrane, and roof outlets and drains that are misaligned with the low spots of the roof.
The Risks of Ignoring Ponding Water
Ignoring ponding water on a commercial or industrial roof creates a lot of problems. Ponding water, in addition to excess weight on the roof, can accelerate deck deflection. Most roofing membranes, especially older bitumen felt systems, are susceptible to UV damage and blistering due to lack of evaporation. Water ponding will also provide a lot of silt and debris around and under the drains which encourages ponding water and algae, moss, and other bacterial growth. In addition, ponding water also increases the risk of leaks for businesses below by forming ice in the winter and water leaks at an unfortunate time by either flooding or ruining the machinery and IT equipment that the business relies on.
A Long-Term Fix: Tapered Insulation
Luckily, ponding water can be engineered out. One long-term, reliable solution is to use tapered insulation during a major roof replacement or a re-roof. Tapered insulation uses varying thickness boards which are designed to create a roof deck that is sloped and helps to guide rainwater to the drain. This method is more cost effective on larger commercial roofs, as an unresolved design flaw will allow water to be trapped on a large surface area.
Maintenance Steps That Help Right Now
Not every roof requires a full renewal. There are routine tasks that can be handled while a roof is not yet due for complete renewal. A scheduled maintenance visit should be used to clear out outlet and gully blockages. Depending on the slope of the roof, some outlets or scuppers can be added to flat and low slope areas. In addition, tapered insulation inserts or firring pieces can be added to a flat roof to direct water and improve drainage. If there is an area of a roof that is sagging, the firring pieces can be added. A full roof survey would be beneficial, especially after a heavy rainfall to help identify which areas would be best to implement the recommended corrective measures.
Don’t Wait for a Leak
Ponding water is an indication of a greater issue on your property, and it will continue to deteriorate. Structural or drainage issues are likely causing ponding water on your property. Waiting to address the issue will cause the cost and catastrophic damage to your property to increase as the issues worsen. Addressing the standing water issue promptly saves a roof, the stock, and equipment it protects, and the business it houses. It is less costly and more preventative to schedule an evaluation once water starts standing instead of waiting for a leak.
