Should Your Flat Roof Be Sloped?

That is a question that comes up from time to time. Building owners often find water pooling on the roof, or it is draining in the wrong direction. This is not caused by poor workmanship when the roof was installed; instead it happens with some roofs. A flat roof, over time, can develop sagging in the middle areas or the building itself may settle and cause the roof to be more sloped towards an area where there are no drains. The effects of this settling are ponding of water, and leaks around structures and equipment that protrude from the roof. Water naturally ponds on a roof but if the water lasts more than three days after a rainstorm, you may have a potential problem forming. If you have a smaller, residential roof, ponding water should not last for more than a day.

Flat roofs, due to the poor accessibility and low visibility, tend to be overlooked for routine maintenance. The roofing material that is used on a flat roof is designed to last 10 years or more, but if water sits on it for long periods of time, it slowly deteriorates the waterproof membrane that keeps water out of the building. By the time a leak is noticed, damage has already occurred to the roofing material and worst-case scenario, the roof framing may have started to decay. When this happens, a major and costly repair is required.

What are some things you can do to prevent this from happening?

The least-expensive option for most building owners is to schedule regular, routine maintenance by a qualified roofing expert. They will come and inspect your roof for problem areas and can make suggestions to increase the life of the roof. This simple task can save the building owner a lot of money down the road. More often than not, this task is overlooked until a problem arises.

Worst-case scenario

So, you have taken the latter suggestion, and now you have a major leak in your roof or have noticed a large area where water is ponding on the surface of the roof. What can you do to save your roof?

Unfortunately, you may have ignored your flat roof too long. In situations where there is problematic ponding or the slope of the roof has changed, due to settling, and is now creating a drainage issue, there is no cheap alternative. This is seen in quite a few instances each year. Patching the problem area is not feasible as the leak will just reoccur down the road. What you need now is a roof makeover. You need the help of a flat roofing expert who can fix the problem and prevent it from happening again.

Some may think all is lost, and your building is going to have to be torn down and rebuilt. This is not the case, unless there is major damage to the structure but that is an extreme case and usually only occurs in abandoned buildings. What you have now is a problem, but one that can be fixed.

Buildings naturally settle, and due to the large span of most commercial flat roofs, the middle areas can buckle under the weight of snow, ice, and simply time. What solution will work for your roof may not work for the neighbouring roof so you really need an expert opinion before you jump to any conclusions.

What are your options?

If the ponding is not too bad or the water is draining in the wrong direction, oftentimes a new drain will be installed to take away the excess water. This drain ties in with the other drains on the roof and usually solves the problem of ponding or poor drainage. This solution is relatively inexpensive compared to others.

If a new drain does not solve your problems, then you have to get more radical in your solutions. This is where a roof will often require a partial or total rebuild. The roofing contractor can advise you on what is best for your roof. If the recommendation calls for a partial rebuild, oftentimes the contractor will build up the area which has sunk and is causing the ponding. A slight incline, going each direction can be used to drain the water from the lower areas of the roof. This is kind of like putting an umbrella on your roof to shed the water. This works when there is good drainage elsewhere, and the problem is situated to one area of the roof.

A more drastic option requires the roof to be rebuilt and a slight slope be incorporated into the roof. This is a major undertaking and is rather expensive so it is generally only done with extreme cases.

In this situation, the roofing contractor will build up the roof using a combination of materials like wood, foam, or specialized materials designed for flat and low sloped roofs. The entire roof must be sloped and proper flashing installed around vents and mechanical structures. Before doing any work on the roof, the structure must be inspected to ensure that it can hold the additional weight of the new materials being introduced.

When building the new slope, the roofing contractor will install new drains to shed water from the roof quickly. Mechanical equipment on the roof can sometimes contribute to the ponding water. Condenser units from air conditioners can create large volumes of water, so they must have proper drains installed nearby to prevent further ponding.

In both situations, where a portion of the roof is sloped or the entire roof is sloped; a new waterproof membrane must be installed just as it would a regular flat roof. It is installed in the same manner and seals the roof from further damage.

As you can see, owning a flat or low-sloped roof requires you make an investment in preventative maintenance to avoid costly repairs. For every dollar you spend on maintaining and inspecting your roof, you will save you countless dollars in needless repairs. Just because you can’t see what is going on over your head doesn’t mean that you can ignore it. Spend a little money and have a professional roofing expert come and inspect your roof before there is a leak or something major goes wrong.