Sags on flat roofs are a sign that your roof has a problem. These roofs should be level and even. If you notice dips and hollows on the surface, then you should have the roof checked. Why do flat roofs sometimes sag?
1. Water Drainage Problems
If water can't drain off your roof, then it will sit on the surface. This can be down to problems in your drainage system, such as clogs.
Or, it can be a sign of a long-term ponding problem. If a lot of water sits on a flat roof regularly, then it can create dipped areas. It might seep into the roof's underlying materials and supports and cause sagging and rot problems. This is a sign that the roof no longer has the support it needs to stay level.
2. Weight Problems
Flat roofs can sag if they have to deal with too much weight. For example, if heavy snow sits on your roof every winter, then its weight can cause some structural damage. Or, if you have solar panels or HVAC units on the roof that don't have adequate weight support, then they can damage the part of the roof they sit on. They can compress and break support materials creating dips on the surface.
3. Foundation Problems
Over time, buildings shift and change position. Their foundations don't always stay in exactly the same place. While this can be a sign of a serious structural problem in a building, sometimes these shifts are normal movements.
However, any movement in a structure can affect a flat roof. When the roof was installed, it was made level and even. If its core structural support changes position, then the roof might start to dip in some areas. Even a small foundation movement can affect the position of the roof.
If your foundation movements are not a problem in themselves, then you might need to tweak the roof to make it even again. This might involve building the roof up in some areas or adding additional supports.
4. Age Problems
While flat roofs are designed to last for years, they will lose some of their working efficiency as they get older. Their supports, insulation, and surface materials might wear and break. They might develop cracks or gaps which allow leaks into their structure that affect their support.
Age and its related damage can affect the level of a flat roof. The roof might look sound; however, it develops underlying problems that make it sag out of position.
In some cases, you can fix sags on flat roofs; however, sometimes a full roof replacement is a better solution. To find out more about your problem and the best fix for it, contact a local roofer. For more information, contact a roofer near you.