The purchase of a commercial building with a flat roof may be surrounded by numerous tasks and activities, with most of the attention going toward moving in and getting open for business. Prior to finalizing the purchase, however, you should dedicate some time to conduct an inspection of the roof to ensure that there aren’t any existing issues or problems that will crop up shortly after escrow closes.
1) Inspect the interior of the structure – Take a look at each room in the structure, focusing on any evidence of leaks, including dark water stains and bubbling paint. With flat roofs, water from a leak can travel across structural elements such as beams and framing before dripping through the ceiling, so keep in mind that water may not be entering the building directly above the stain. Bubbled paint on walls may also be indicative of a roof leak where water is running down the interior sides of the structure rather than pooling in areas above the ceiling.
2) Check the roof – The absence of water stains and/or bubbled paint in the structure does not guarantee a fully functional roof, as leaks can go on for months without damaging the interior. When checking the roof, look for any physical issues such as blisters, cracks, or pooled water. When you’re walking on the roof be aware of any areas that feel soft or spongy, as they may be rotting due to exposure to moisture that has found its way past the outer layers of protection. Be sure to inspect the flashing around structures that penetrate the roof deck, such as vents and pipes, as these areas are commonly associated with leaks. Look for any signs that flashing and/or seals are cracking or are pulling away from vents, fan housings, and pipes.
3) Drainage – One of the biggest challenges with flat roofs is maintaining adequate and efficient drainage, which minimizes stress from bearing the weight of standing water as well as the potential for leaks. If you see standing water or evidence of pools that have evaporated, check gutters and drains for blockage. Downspouts may not lend themselves to visual inspections, so do a test by running water into each one and check the drainage flow at the other end. If water is draining slowly, you may be able to use a machine similar to those used by plumbers that runs a snake through the drainage pipe to break up the debris that has caused the clog.
These inspections are relatively easy to do, especially checking the interior of the structure for signs of problems. There are, however, many subtle signs of potential problems with flat roofs that may only be detected by a trained eye. In these situations, the money spent on a professional inspection is often a solid investment that catches trouble earlier rather than later.
If you live in an area where the daily temperature range in winter runs above and below freezing, there is a good chance that one or more forms of the freeze/thaw cycle is at work on your roof. Here are 3 examples.
- The cause – Ice dams form through uneven heating of a roof that is holding an accumulation of snow. In most cases, uneven heating is the result of heat radiating through the attic of the structure while the area over the eaves stays much cooler. If the difference between these two areas is great enough, snow over the attic will melt and drain toward the eaves where it refreezes; forming a ledge that subsequently collects runoff that is trapped over the warmer part of the roof.
- Potential damage – Trapped water can back up under shingles and saturate roofing materials, which speeds the deterioration process. If the process is far enough along, trapped water can start leaking into the structure. If an ice dam and the amount of water trapped behind it become large enough, roof damage may also result from bearing the excess weight of ice and water.
- Solution – If you see evidence of the formation of an ice dam, such as a preponderance of icicles, call a professional for immediate removal. To prevent ice dams, add insulation to your attic to reduce the heating of the roof.
Small spaces between roofing materials:
- The cause – Water finds its way in to spaces between roofing materials, which can occur when it pools behind an ice dam. If this water freezes in these spaces, its expansion can push roofing materials apart by microscopically small distances at first.
- Potential damage – Given enough time, these tiny movements can allow increasing amounts of water into the space to freeze, expand, melt, and repeat. This can ultimately lead to a significant weakening of the roofing system.
- Solution – Handle ice dams as quickly as possible and conduct regular inspections to address issues as quickly as possible.
The gradual separation of flashing from the chimney, vents and other structures that penetrate the roof deck:
- The cause – Flashing, which is purposed for channeling water away from roof penetrations, can start cracking and or separating from vents, chimneys, ducts, etc., which provides the opportunity for water to enter.
- Potential damage – Much like the freeze/thaw cycle in spaces between roofing materials, frozen water gradually makes these deficiencies larger, thus allowing more water to enter, which facilitates more damage.
- Solution – Inspect flashing regularly and seal any cracks that appear. If flashing is damaged, call for immediate repairs.
The damage of a freeze/thaw cycle on a roof can be subtle at first, but significant later. If you live in an area that regularly experiences freezes and thaws, the best courses are to take preventative actions where possible and inspect your roof regularly.