Flat Roof Drainage and Leaks: It May Be Plumbing and NOT the Roof

General Roofing Systems Canada provides Flat Roof Repairs throughout Canada. Repairs are completed in the following cities: Calgary, Red Deer, Edmonton, Fort McMurray, Lloydminster, Saskatoon, Regina, Medicine Hat, Lethbridge, Canmore, Banff, Cranbrook, Kelowna, Vancouver, Whistler, Winnipeg, Toronto and points between. British Columbia. Alberta. Saskatchewan. Manitoba. Ontario.

Below you will find a simple account of a service call inquiry. Oftentimes, there are multiple contracting parties involved in a roof repair. This includes plumbers, the roofers themselves, other construction services in the area, and obviously the stakeholders themselves.

In this case, a simple misunderstanding concerning the purpose of water testing culminated in repeated requests for service calls outside of the ongoing work we had been performing for the client. Finally, our client’s property manager provided us with the implements to deal with the problem. As suspected, it was the plumbing – not the roofing system itself – which was causing major leaks.

We have included a comprehensive explanation from our national project manager as well as a follow-up correspondence by a third-party plumbing contractor concerning this matter.

Water Source Needed to Test Drainage System

As you know, for about a year and a half, GRS has been requesting a water source at the building to be able to test your drains. On each occasion, we have been told that a water source is being to be made available. As well, our crews have been told that it is likely the water source has been covered up in construction, but that we may be able to use a neighbour’s water source until a proper solution could be found. Up until today, no water source has been offered.

The Reasons Drains Need to be Tested

a. The source of the leaks were previously at the drain system. We requested the drain assembly (the connection to a new drain and U-Flow, and the connection to the drain) be redone with a plumber – we would provide the roofing services and the plumber would provide the connection services. This was not done at that time. My understanding is that the plumber only cleared the drain system. So, we requested a water source so that we could test the drains/plumbing ourselves to eliminate them as the main issue, or conclude that they are the suspected cause of your leaks.

b. The plumbing system and assemblies are old. It is common for drainage during times of heavy rain (which is when your building is having issues) to back up and leak at the drain bowl assembly connection to the drain pipes. As the water rises and then meets the bowl assembly, if there is not a U-Flow expander and/or proper drain bowl, the water will then get between the pipe and the connection to the bowl. What occurs is the water that is backing up will then get into the roof assembly and begin to run along various areas and manifest themselves through the ceiling. At the time of your roof replacement, there was no work order for the plumbing and drainage to be modernized, and normally this is not an issue. This this does become one, it is typically solved with a quick water test and simple remediation work (such as bowl replacement, U-Flow backup expander installations, and/or repairs to the drain pipes).

Discussion with the Site Manager

Water testing only works when it is not raining and is intended to isolate the drainage system from the roof membrane that we replaced. This is the reason for the need of an external/outside water source. We test the drainage system with a hose, which allows us to isolate the drainage system on its own. If that test does not show that it is the drainage system, then we go on to retest the membrane. We also test various other penetrations, such as rooftop units and/or vents, pipe boots, etc. Finally, we move onto testing various other components of the building envelope, such as the connection of the roof to the wall and the flashing areas.

Your site manager also asked that an emergency be done (such as pumping water off the roof), to which I replied that we could, if requested, dispatch an emergency crew for that, but we would have to charge extra because we have requested on numerous occasions for the water test to be done to the drainage system, and that has not been done. The site manager did not seem to want the emergency service under those terms.

I should also note that on the other occasions that we did respond in this fashion, that we did not charge for the emergency service. We did this despite finding that it was a drainage problem by the plumbers at that time. Furthermore, I will also note that on each occasion we did recoat the roof and did not charge for that either.

The only reason we are now saying that we have no choice but to charge a service fee is because we have requested number times to have water access. Part of our servicing parameters included that should the water test not to be done, that we would charge a fee for the emergency service.

You also asked us about why water was pooling on the roof. I explained to the site manager that at the time of the roof replacement, an engineered sloped insulation package and rebuild of the building exterior (parapet wall construction, sheet metal, siding, etc.). We were only approved to go ahead with the roof membrane replacement only. He asked why that was so, and I said that it is an option and that not all (in fact, less than 50%) of the buildings we service have a sloped insulation package installed. I directed him to all the neighbouring buildings as examples of those that do not have such sloped systems.

Discussion with the Property Manager

I explained to the general property manager that we needed to test the various components of plumbing, membrane, units, vents, plumbing boots, and possibly the building envelope at the roof to wall connections. Finally, we have been promised an external water source to isolate the issue based on our tests.

Plumbing Contractor’s Follow-up with the Property Manager

August 21, 2015:

I was sent out to have a look at water leaking in the building. I found that the roof was full of water and it is what was pouring into the suites. The one drain was working, but very slowly. I called in the drain cleaners and went through it with them.

The snake was getting caught up on something, so I had them use the camera and we found there is something stuck in the piping. We traced it to the piping in the ceiling of a first floor room. We will need to return when the water is all gone and open the ceiling, remove the piping, and then get the cause of the blocking out. As it stands, the system is draining as much as it can with whatever is causing the blockage.

Also, the building has some piping up to the roof drains. These are not ran well and are back-graded for parts of the system. I have left it disconnected for the drain that has the problem.

General Roofing Systems Canada (GRS)
24 Hour Emergency Roof Repair: Call +1.877.497.3528 toll-free.


Calgary, Red Deer, Edmonton, Fort McMurray, Lloydminster, Saskatoon, Regina, Medicine Hat, Lethbridge, Canmore, Banff, Cranbrook, Kelowna, Vancouver, Whistler, Winnipeg, Toronto and points between. British Columbia. Alberta. Saskatchewan. Manitoba. Ontario.

Flat Roof Sagging | Re-Roofing Residential Flat Roof

General Roofing Systems Canada Repairs Flat Roofs throughout Canada. Flat Roof Repair; Calgary, Red Deer, Edmonton, Fort McMurray, Lloydminster, Saskatoon, Regina, Medicine Hat, Lethbridge, Canmore, Banff, Cranbrook, Kelowna, Vancouver, Whistler, Winnipeg, Toronto and points between. British Columbia. Alberta. Saskatchewan. Manitoba. Ontario.

Note to reader:
We have begun posting common roofing questions that we receive to our website, blogs, and on phone lines to assist those researching answers to their roofing problems. We edit out any personal information (denoted by ‘—‘) for obvious confidentiality reasons prior to posting. If you have a roofing question, email us at info@grscanadainc.com and we will do our best to help you with your inquiry.

The inquiry came from a residential flat roof owner from Red Deer, Alberta that is considering preventative flat roof maintenance or flat roof re-roofing, as her flat roof is beginning to show signs of fatigue. Water is pooling or ponding and not vacating through the gutter system. The flat roof’s age is nearing 30 years, which is very near the end-of-life for a tar and gravel system. The flat roof is now very likely beginning to sag.

This particular inquiry is common. During the period that this residential roof was installed, flat systems were popular. Common residence types included revenue properties and duplexes, as well as high-end homes. The architects during that period specified many flat roof homes and many of those systems are now in the process of re-roofing or roof recovery retrofits.

Client Inquiry:

Hello; I presently own a house in Red Deer where the house is presently 25 to 30 yrs old. It has a tar and gravel roof which has given me no problems whatsoever. However, I am looking at preventative measures. The neighbours in the crescent are all starting to re-roof their homes, now I am most likely considering the same.

I found this year that the water is not going into the eaves & it is becoming a concern, so I have decided to look at what could be causing this & the option of putting a roof over the existing one.

Do you re-roof in Red Deer, and if so, could you please come by and give me an estimate & advice? If you do not work in Red Deer, do you know of a reputable company who has experience in this type of roof?

Our Response:

I am the fellow on-call tonight (we run a 24 hour emergency roof repair service) so I thought I may as well respond while I have a few minutes – I’m your Regional Project Manager in Alberta.

To answer your questions:

We do work on roofs in Red Deer regularly. We do not have a physical office in Red Deer but it doesn’t make any difference as our trucks are going from Lethbridge to Calgary to Red Deer to Edmonton and Fort McMurray all the time. We regularly have roofing crews available in and/or through Red Deer.

That makes me wonder if the Calgary to Edmonton corridor will ever get a light rail high speed train system – not likely, but it sure would help me transport our roofers efficiently….

Sorry, yes – we do work in Red Deer and we do re-roof residential flat roofs on homes and we also do flat roof recovery systems as well.
My suspicion is that your tar and gravel flat roof, being that the roof is almost 30 years old, even though it isn’t giving you any trouble now, will be trouble soon. Of course, without a roof inspection and flat roof assessment performed on site, it is impossible to say, but your roofing system “symptoms” (it sounds like the flat roof system is sagging) are typically a precursor to roof system failure of some sort (leaks or even complete failure).

As the flat roof membrane begins to sag over the years water begins to pond and the process of degradation of the roofing layers – tar paper and bitumen occurs relatively quickly from there on. Also, the layers of roofing will typically begin to tear, become brittle from the sagging of the roof and exposure from the UV. Nonetheless, in saying that, there are ways to delay the re-roofing of your flat system or performing a flat roof recovery by exercising roof repair options.

So yes, we should take a look at your roof. Roofers are in “that season” now and roof assessment scheduling is tight. I am thinking I will have an opportunity some time —- as I am between Edmonton and Calgary 3 or 4 times between —– . So I will call you when it looks most feasible and give you ample notice – I am thinking —– will likely work for the inspection.

In the meantime, if you have any questions, feel free to call us anytime 877.497.3528 toll free or on my direct line(s).

Thanks for your inquiry and we will see you soon!


Until next time,

The Team at GRS

General Roofing Systems Canada (GRS)

24 Hour Emergency Roof Repair: Call +1.877.497.3528 toll-free.


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