The most common symptom of a roof leak is bubbling paint or stains in the ceiling gyproc. Sometimes the leak appears at the ceiling/wall joint, sometimes it is becomes visible at the seam tape between the gyproc panels. At times, it is not subtle at all, with a large amount of water running down the walls or dripping onto your floors. Other times, the leaks are very subtle, and don’t show up as interior damage at all, but do let water into the attic or the cold spaces.
The first thing to figure out is whether this problem is new, or whether it has happened before. If you’ve lived in the same home for more than a few years, and you’ve never seen it before, then chances are excellent that something changed recently, and therefore contributed to the leak. If you’ve been in the house for under two years, then it is possible that the former owner did not disclose the history of prior leaks, and therefore the leak you see for the first time, may in fact be a long-standing issue that was hidden by new gyproc and/or paint.
There are many possible causes of roof leaks. For “new” leaks, common causes are:
- ice dams
- gutter/eavestrough icing
- wind damage to roof cover
- failure of caulking or sealant
- physical damage to the roof surface by falling objects or ice
- failure of a waterproofing layer
- installation of a bathroom, kitchen or drier outlet into the attic
- Installation of pot lights or recessed ceiling lights
Other leaks, especially if they have been present for a while, are often caused by:
- poor installation of waterproofing layers
- poor design and/or installation of flashings
- use of inappropriate products to cover or waterproof the roof
- incorrect amount of ventilation and/or insulation for the roof design
- poor detailing of roof penetrations (air vents, plumbing vents, electrical poles, etc.)
- poor design of roof/wall flashings
- leaks in caulking at window and skylights
- poor placement of vents and other roof openings relative to wind direction
If there were short-cuts taken during the installation of the last roof, then these usually contribute to making the original problem worse. For example, some roofers advocate leaving the old roof on because it gives “extra protection”. When a leak DOES happen, then the layers of old roofing provide an additional path for water to run in different directions. Other times, they “save you the cost of new flashings” and reinstall the old flashing – this works until the water finds the holes. Still other times, the various materials were not installed according to manufacturer directions, and therefore did not provide the appropriate waterproof seals that were expected (this is a common installation failure for waterproofing membranes).
It is common to find that there is not a single point of failure, but a series of weaknesses that contributed to allowing the leak. For example: The primary cause is an ice dam, which allowed water to find a poorly-caulked joint, when then ran onto waterproofing membrane until it found an open seam, and then into the roof. Once it entered the roof, it ran on the underside of a beam until it came across a supporting strut, at which point the water dripped down onto the insulation, and through the insulation onto the vapour barrier. Then it pooled on the vapour barrier until there was enough to direct it to a gap in the vapour barrier, and onto the gyproc. It finally showed up as bubbling of paint on a gyproc seam. Where it came in can be quite far from where the leak actually occured. So when looking at a source of the leak, it is necessary to play detective, and follow the water trail. Sometimes it is quite easy. Usually, it is not.
In the above example, the solution (short-term), would be to remove the ice dam, and to dry out the accumulated water on top of the vapour barrier. However, the long-term solution is to add enough insulation to prevent the melting of snow in the first place, then have enough ventilation to remove any residual heat leaking past the ventilation and any moisture that may be entering the attic. When the roof gets redone, the membrane needs to be properly applied (right product, right installation method, right location), following by the appropriate flashings, and finally counterflashings and caulking.
In some cases, we’ve seen roof covering deteriorate to the point that water is freely running on the underlayment, and every gap in the underlayment allows entry of water through the nail-holes and other breaks in the underlayment surface. If the decking is made from OSB (Oriented Strand Board) of the Exposure 1 grade, then there is a high probability that the decking will be damaged extensively as well, and will need to be replaced. If the leakage has occured over a period of time longer than one year, then there are also mold issues to consider.
In short, a leak is telling you that there are potentially major issues to be dealt with. Before throwing money at the problem, take the time to figure out what’s actually going on, and what the priorities should be in terms of fixing the problems in both short and medium terms. If you contacted your last roofer and he claims that there’s no problem (that he’s responsible for fixing), maybe it’s time for a second opinion. After this, you will have a better idea of what the problems may be, and what would be a reasonable approach to getting them resolved.
(c) 2013 Paul Grizenko