Flat residential roofs can suffer from puddling, which is when water collects on the roof surface instead of draining off. There are a few reasons puddling occurs, and they can all be repaired and prevented. 

1. Pitch Junctures

For roofs that use a combination of flat roofing adjoined to a pitched roof, there can be a slight dip at the junction between these two roof planes. This results in puddling water and a weak junction that is more prone to leaks. A roofer will either install a mid-roof drain or they will alter the roof structure to get rid of the dip. In some cases, both a new drain and a slope repair are needed.

2. Tree Debris 

Trees overhanging your home may provide some nice shade, but they can also cause problems on a flat roof. Dropped leaves or branches can collect on the roof surface, creating obstructions that trap pooling water on the roof. Not only can this lead to leaks but the excess weight of water and debris can also lead to roof collapses. Trimming back trees, cleaning the roof, and repairing small damages as they occur are necessary tasks. 

3. Inadequate Drains

Residential flat roofs typically have drains around the roof perimeter, which may simply flow off the roof or they may feed into a gutter and downspout system. Some roof designs also have internal drains at low points on the main roof surface. Damaged or blocked drains may fail to work properly, leading to puddling until they are repaired. In some cases, there may be too few drains and your roofer will need to install more.

4. HVAC Problems

Many homes with flat roofs have the HVAC unit installed on top of the roof instead of next to the house. This saves space in your yard, but it can cause issues on the roof. Puddling can occur around an HVAC unit due to leaks from the unit itself, which will require an HVAC repair to solve the problem. The unit may also block water flow off the roof, which can be fixed by installing a shuttle to route water around the HVAC unit.

5. Penetration Dips

Penetrations through the roof structure, such as where a skylight sits or a plumbing vent protrudes, may pose an obstruction to water making its way toward a roof drain. The puddling will occur behind the penetration, on the slightly upslope side. Your roofer can install a shuttle in this location, which will route any water around the penetration so that drainage isn't impeded. 

Contact a residential flat roofing contractor to learn more.