How and why flat roofs leak.
Leaks on flat roofs are notoriously difficult to locate. Sometimes the weight of rooftop equipment, such as HVAC units, causes subtle slopes in the roof. Generally, guttering or a drainage system is installed on a roof to control water. Without a true “slope” to follow, the site of a leak may be difficult to find on a flat roof. Often, leak damage goes unnoticed while water continues to penetrate and soak the underlying decking and insulation.
If left unrepaired, this can weaken the roof structure and present other expensive and potentially hazardous problems.
Flat roofs are generally covered with some type of membrane or metal sheets. If water penetrates the covering, the water can travel quite a distance before it causes visible damage or leaks into the building. If the decking and/or insulation is saturated, this can cause puddles of water and additional weight.
A lack of drain maintenance is a common cause of leaks. Gravel, leaves, and other debris can drift with the water to the drain and become lodged. This blocks the water outlets. Water cannot drain away and begins to build up, causing a pressure head of water that can force water into even the smallest hole on the roof. This water can freeze and expand under the roofing surface, causing a new crack or an existing one to grow larger. This freeze and expansion of water can occur if water enters any hole or crack on the roof.
Ponding water is another concern. Similar to a drainage issue, if a portion of the roof has a slightly lower pitch than the rest, water may accumulate there. Especially with EPDM roofs, the water can accelerate membrane degradation. Organic material may also use glue as a food source. Water is said to be ponding if it remains standing on a roof more than 48 hours after a rain ceases.
Seams are another frequent source of leaks. Any point where materials overlap – even metal sheets – has the potential for a leak. Many flat roofs use rolled sheet goods such as EPDM or PVC. These are bonded together to create seams. Many installers weld the seams on the rooftop. The labor and skill of the installer plays a large part in the quality of the roof protection. LaFerney Commercial Roofing uses a single-ply membrane that features a factory heat-welded bond. With the seams sealed under ideal conditions in a controlled environment, the risk of leaks is reduced by 85% before the membrane even arrives to your facility.
Flashing is another common source for leaks. Flashing is generally installed at any roof transition, such as at a pipe, stack, skylight, or a wall. Flashing should overlap the roofing membrane in such a way that water is deflected away from the transition. Flashings should be free of cracks and there should be no lift in the seams. With many roofing systems,the required shape for flashing is made while on the roof. The quality greatly depends on the skill level and training of the installer. LaFerney Commercial Roofing offers flashings pre-fabricated at the manufacturing facility, again under ideal conditions.
The pre-fabricated flashing is made to specifications for each penetration. The flashing is then heat-welded to the membrane by our highly-trained installation crew. This pre-fabrication process further reduces the risk of leaks and expedites the installation process. The risk of error or improper fabrication by an installer is effectively mitigated.
LaFerney Commercial Roofing offers walk pads to reduce potential damage to the membrane from areas of high foot traffic such as access doors and equipment requiring regular maintenance.
If your roof is leaking, or if you are concerned about the possibility, please contact LaFerney Commercial Roofing for an evaluation. In the words of Don LaFerney, Jr., “The leak stops here.”