Converting a Tar-and-Gravel roof to metal or membrane

If you have a tar-and-gravel low-slope roof (typical of constructions in many areas in Montreal), you may consider changing the roofing material to something else.  Two common alternatives to tar-and-gravel are two-ply membrane assembly and standing-seam hidden-fastener metal panels.

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Some myths about roofing

Most people think they have a good grasp of how roofs work – the shingles (usually asphalt) keep the water out, and that they do that by being the waterproof layer that stops water from getting in.  That’s more myth than fact.

Another myth, is that caulking is an acceptable way to achieve waterproofing.

Another myth, is that if you have ice-and-water shield on your roof, you’re good.

What all these myths have in common is that they misunderstand how a sloped roof system works in reality.

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Case study – poor workmanship in an aluminum shingle roof install, investigated in 2008.

We were asked to diagnose a case of roofing materials being damaged by sliding snow and ice.  The covering materials were made from Interlock Finall aluminum shingles.  The company that carried out the installation was “no longer in business”.  While carrying out the inspection, I witnessed many elements that I considered substandard, and workmanship which was quite appalling.  The photograph documents one location where a number of deficiencies were found.

Example of poor detailing on an aluminum roof install.

Example of poor detailing on an aluminum roof install.

The area in the photograph is the lower part of a roof, adjoining a wall.  The correct approach would have been to do this part in the following manner:

  1. The sidewall flashing is removed.
  2. The old roof covering is removed.
  3. A base flashing (about 4”x4”) is installed the length of the roof-wall join, and waterproofed with roofing cement.
  4. Water-proofing membrane (ice-and-water-shield membrane or other peel-and-stick membrane) is installed along the roof/wall joint, running about 4” up the wall, and extending past the eve by about 1-2”.  To ensure adhesion to the metal base flashing and the brick, the area is first primed with roofing cement.
  5. A width of water-proofing membrane is installed along the eave, with about 1-2” of membrane extending past the eave, to protect the upper portion of the fascia board.  The membrane is 36” wide, so the eave is covered by membrane along the eave to a height of about 34-35”.
  6. The rest of the roof surface is covered by synthetic underlayment, to provide cover for the roof until the covering is installed, and to provide a water-proof barrier to any condensation that will occur under the metal surface after installation.
  7. A starter flashing is installed along the base of the eave, to provide an attachment point for the shingles, and to ensure water cannot enter the roof system.  If there is a gutter, the membrane need to be BEHIND the gutter (ie, between the gutter and the fascia board), and the fascia portion of the starter flashing should be OUTSIDE the inner gutter wall, so the water is directed into the gutter.
  8. A side-wall or end-wall flashing is installed along the roof-wall to a) provide a solid attachment point for the shingles, b) to prevent water entry, c) provide a drainage path for any water entering the join at that point, and d) to create an esthetically-pleasing transition detail between the roof and the wall.  The vertical height of the flashing is usually determined by the amount of expected snow accumulation, with the top being ideally at least an inch or two above the expected snow height.
  9. At the join of the endwall flashing to the starter flashing, the endwall flashing is placed OVER the starter flashing so that any water carried by the endwall flashing is directed to the outside.
  10. The shingles are installed, locking into both the starter flashing and the end-wall flashing.
  11. A wall counter-flashing is installed over the top of the end-wall flashing, to ensure that the wall-flashing join is protected from the sun, wind and water.  Depending on the wall material, the counter flashing is positioned into a cut (if brick), or is custom-fitted to follow the contours of the brick or other material.

This photograph documents that many of these steps have not been done.

Step 1 (remove old flashings) – was done.  This can be seen by the residual caulking (greyish in colour) that was left on the brick.  Note that the original counterflashing was fitted to follow the brick grouting.

Step 2 (remove old roof covering) – not done.  We can see the old roof covering (green asphalt shingles) peeking through at “H”.

Step 3 (install base flashing along wall) – not done.  We should have seen the base flashing at the corner of the roof/wall at “H” if it was there.

Step 4 (install waterproofing membrane along roof/wall join) – not done.

Step 5 (protect eave with waterproofing membrane) – not done.

Step 6 (install underlayment) – unknown.

Step 7 (install starter flashing along eave) – done, but poor finishing detail.  The flashing should have extended to the wall, but instead it was cut short leaving the roof/wall/fascia corner completely unprotected (“I”).

Step 8 (install endwall flashing) – done, but poorly.  The endwall flashing (running up the wall under the counterflashing), is cut short at the base (see “G”), and does not overlay the starter flashing.  It also does not go up the wall high enough to prevent water entry if water-saturated snow has accumulated on that roof section, and the flashing itself does not appear to have a internal safety bend that would keep the water in a channel.

Step 9 (lap endwall flashing OVER starter flashing) – not done.

Step 10 (install shingles) – done.

Step 11 (install counterflashing along wall) – done but poor workmanship and detailing.  There was no attempt to “marry” the flashing to the brick.  The counter-flashing was poorly bent (see “C” – edge of bent is not crisp and straight, so it appears this was done by hand), the flashing was effectively glued to the wall with caulking (see “B”), with two fasteners holding it to the wall (see “A” and “E”) causing buckling (see “D”).  The counter flashing should have extended past the end-wall flashing at the eave, but was terminated much earlier (see “F”).

Because of the many short-cuts taken, water entering the gutter can go and enter the fascia board at “J”.  It can be also seen that the gutter is loaded with ice in winter, and has been deflected downwards (see the break in the old caulking at “K”).

The point of this analysis is to show that the pesky little time-consuming details matter in giving a good end-result.  Giving the illusion (appearance) of having metal installed without paying close attention to the details, is not sufficient when protecting the roof and related structures against the elements.

(c) 2014 Paul Grizenko

Roofing materials – what choices do you have? Part 2

Let’s have a look at the typical products available in the Montreal area.

Asphalt shingles in all their various forms, constitute anywhere from 50% to 95% of the installed roofs (for sloped residential roofs) with the proportion depending on the area of the city or region.  They are the cheapest form of roofing, are readily available from any number of sources, and are the easiest to install.  They also are not waterproof, can easily blow off (if not properly installed), and usually last from 10-15 years.  The exact kind of weakness they show depend on the type and brand of shingle, but in general, even with good installation practice and proper preparation, they usually don’t last much beyond 18 years.

Tar and gravel roofs are quite common in certain areas of the city, and are found on flat and lower sloped (2:12 to 3:12) roofs.  They were very inexpensive to install, and generally last 20-30 years.  However, given that they are “built-up roofing” made from successive layers of tar paper embedded in roofing tar, they depend on good installation practice both in the laying down of the basic material, and in the flashing details at the roof perimeter and any penetrations.  At this time, the number of companies that continue to do this work is much less than before, and they tend to be large commercial outfits.

 Membrane roofs are now seen more and more, replacing the tar and gravel coverings on low-slope roofs.  These membranes are of different construction and use different materials, but the most common is a form of modified asphalt sheet (usually two-ply), that is installed in overlapping layers.  There are different installation methods, with some being glued down, and others requiring open flames to melt and seal the layers.  The latter is called “torch-on” membrane, and should be installed only by insured craftsmen.  Durability and effectiveness depends very much on the installation skill and detailing, but a well-installed membrane roof should last about 20-25 years.

 Metal roofs were very common in our region before asphalt shingles became the common material, partly because of our snow loads – they allowed the snow to slide off and reduce the load on the roof.  Since those times, metal roofs evolved in a dramatic fashion, creating products such as standing seam roofs, steel, aluminum and copper shingles, various profiles of metal panels that resemble clay tile, or wood shake, or architectural asphalt shingles.  The roofs range from very cheap (generally thin screw-through panels) to very expensive (hand-made copper or stainless steel coverings).  Most metal roofs come with 50-year (give or take) product warranties, and if properly installed, can be expected to last over 100 years.  On the other hand, the choice of which metal product is most appropriate for a given situation is something that many homeowners just don’t have the knowledge to make, and are very susceptible to the salesperson pitch.  Proper installation also plays a very important role in the actual longevity of the products, and this is also an area where most people just don’t have the experience to ask the right questions.

Wood or cedar shingles used to be very common roofing materials, but with the disappearance of first-growth cedar, the prices have skyrocketed, and these products are available usually only on high-end homes.  Being a natural product, they have a unique appearance, but also require a certain amount of maintenance and care to reach their potential life.  They have to be installed in a manner that allows them to shed water and to drain well, so that there is little chance of trapped water promoting rot.  Installing these is a very skilled trade, and there are only a few contractors in our region that do a proper job.

Slate is a relatively common material for roofing, especially in areas like Westmount and Outremont.  It is a beautiful, historic covering, and properly installed will last well over 100 years.  However, both the material, and the skilled labour needed to install these is quite expensive, so these are now found only on high-end homes that can handle the weight, and whose homeowners can afford to pay for the maintenance.

Clay tile (and its cousin, concrete tile), is a very common material in many parts of the world, and is found also in our region.  However, in addition to the weight, our frequent freeze-thaw cycles wreak havoc on any tile that has a crack forming on it.  In addition, most homes are not designed to hold up the amount of static weight that such a roof will represent.  Maintenance is also an issue, since these are relatively fragile, and should not be walked on.  We find that homeowners often choose to replace these with metal products that have a similar appearance, without the fragility of true clay.

There are newer materials coming onto the market, including fake slate made from recycled plastic and rubber, and fiberglass panels.  Time will tell whether their initial attractiveness will last or whether the UV exposure and temperature extremes will cause damage.  Earlier versions of these products came onto the market and were withdrawn after frequent failure.  Maybe the new generation will finally get the mix right.

One important consideration in choosing a roofing material, is the life-cycle cost.  What IS the actual duration of the “trouble-free” period for each type of material (and the method of installation)?  Since failure usually starts at the weakest part of the system, it is important to know what that part is, and to do the required maintenance so that part can last as long as the rest of the roof system.

An example of the type of problems that can occur is an asphalt shingle installation over an OSB (Exposure Type 1) deck.  Even when properly installed, some shingles will start letting in water (via the nail holes) in as little as eight years.  Once that water starts entering the OSB decking, the glue starts to deteriorate, and the OSB panel starts losing strength and integrity.  The shingles may still look good on surface inspection, but the seepage pattern visible from the attic will tell otherwise.

A very common waterproofing technique is to use caulking in “waterproofing” various roof joints and penetrations.  The more common caulking formulations lose their resiliency and adhesion in as little as five years, even when properly installed.  Is it a coincidence that most installation warranties (on asphalt shingles) only last 5 years?  The way around this is to build the roof system so that the caulking is more or less cosmetic, with the real waterproofing happening behind/below the caulking.  Ah, but THAT takes more expensive materials, and more labour to install, and besides, it can’t be seen, so why bother?  This detail work is the difference between a waterproofing joint that will last 5 years (more or less) compared to a waterproofed joint that will last 20-30 years or more.

Therefore, when looking at the life-cycle cost, it is important to consider both the material AND the way the product is installed.  Certain materials (like asphalt shingles) are more susceptible to other deficiencies in the roofing system, like improper insulation and/or ventilation.  In addition to “pure” life-cycle costs of the roofing system only, you also need to consider the costs associated with the risks of failure.  For example, if the roofing system fails gradually over time, and there is persistent low-level leakage into the roof decking, then this may be a minor issue if the decking is solid wood, but may be a major issue if the decking is OSB( exposure Type 1).  If the house in question also has ice damming issues (due to insufficient insulation and ventilation), then it is almost guaranteed that there will be serious roofing issues and damage UNLESS the proper preparation and waterproofing was done.

Therefore, in order to make an intelligent purchasing decision when choosing among the various roofing materials available, it is important to also understand the current weakness of YOUR specific roof to know what preparation, waterproofing, and additional work such as ventilation and insulation improvement is needed in order to achieve the promise of what the roofing system could deliver.  Since changing a roof is a major expense for most people, shouldn’t you know that you’re getting the best product and installation for the money you will need to invest?

If you’re not sure about the best fit for your situation, contact me.  We’ll examine your current situation,  determine which factors we need to take into account, and review the options you have.  Now you will be in the best position of knowing what needs to be done and how it should be done, without worrying about whether short-cuts have been taken.  No point in wasting your hard-earned money, and putting your most important investment at risk!

(c) 2014 Paul Grizenko

Ice Dams – Cures, fixes and band-aids.

You have  a nice ice dam, or maybe even several.  The overflow is producing big, picturesque icicles on the outside, and leakage on the inside.  If you’re unlucky, the ceiling is showing signs of falling in under the water infiltration.  What to do?

There are actions you can take now, and then there are various methods of preventing the issue, or finding acceptable ways to live with it.  Keep in mind that the nature of the ice dam changes depending on the slope, the roof-line complexity, the roof covering material, and the prevailing climate conditions.  Therefore, the discussion below may, or may not address your specific situation.

The first order of business is to assess whether the ice dam is causing (or is about to cause) damage.  The damage that can get caused includes leakage into the house, overloading the gutters, and forming potentially dangerous icicles.  Leakage can range from a slow leak, to a massive entry of water.

A.    Immediate Action

Obviously, the first thing to do is to get rid of the water accumulating behind the dam, and then remove the dam because more water will accumulated after if allowed.  How you go about this depends on the type of roof cover you have.  If it’s asphalt shingles, you have to be careful not to damage the shingles when you remove the ice.

1.     Asphalt roofs

Asphalt roofs are designed to shed water.  They are not waterproof.  To render at least the edges of the roof able to withstand water infiltration, the common solution is to use ice-and-water shield membrane along the eaves to provide a waterproof layer.  When roofs leak even with this layer in place, it is usually because not enough of the right membrane was used, it was applied incorrectly, and the installers did not verify the seal of the membrane.

Safety is the first concern on any de-icing operation.  If your roof is walkable and only one story high (bungalow, ranch-style), then it is easy to get up onto the roof.  If it is steep or high, then this is better done by people who have the equipment to do this safely.

Having made sure that you (or your hired help) are safe and properly secured against a fall, it’s probably best to first remove the snow above the ice dam, as this is the “fuel” which will continue to add to the ice dam if allowed.  In doing so, remove the snow down to about 1-2 inches of the roof.  Removing more of the snow, down to the shingles themselves risks damaging the shingles.  We use plastic shovels for this purpose to prevent damaging the roof covering in case the shovel does make contact with the roof.

If there is substantial amount of water behind the ice dam, use a plastic pail or bailer to scoop it out, to reduce the amount of water pressure that is being put on the roof system.

How you get rid of the ice depends on how thick it is.  In the worse case we’ve seen, the ice dam was over 1 ft. thick and the water was about 8” deep.  On that one, we bailed the water, then we used hatchets until we were within several inches of the roof covering.  The last few inches of ice we broke up using hammer blows until we got to the roof covering.

If the situation is not so urgent, you can put de-icing solution on the lower part of the ice dam so that the base of the dam is weakened.  (NEVER put the salt or de-icing solution above the ice dam, as all that will do is make the water that’s accumulating behind the dam even more of a mess, now adding salt and other chemicals to the leakage.)  Once the ice is weakened, then hatchets (used down to several inches of the roof) and hammer blows can break up the ice.

We have seen people try to use hot water, or heating cables, or even propane torches to try and melt the ice dams.  Heat can work, as long as it is applied at the base of the ice dam, and not above the ice dam.  Keep in mind, that if you haven’t removed the water first, and you breach the ice dam, then you will get a large gush of icy water rushing out of its new opening.  If you happened to be doing this standing on a ladder and working on the ice in front of you…  you’re probably now going inside for a change of clothing.

A further issue is what to do with the gutters that are filled with ice, and may have contributed to the formation of the ice dam.  This needs to be assessed on an individual basis, depending on how strong the gutters are, how solidly they are attached, and what kind of material they are made from.

2.     Tar and gravel roof

Tar and gravel roofs generally have a slope of 2:12 or less, and are designed to either allow the water to run off over an eave, or to a drain (or several) located somewhere in the interior space of the roof.  The roof surface is designed to be completely waterproof, and generally there is no need to break up the ice dam, unless the central drainage hole is plugged up and the water cannot drain.  If you DO have this situation, then it’s best to call in professional roofers, who will first remove as much water as possible, and then will try to clear the blockage.  If not done properly, there is the danger that the seals around the drain will be broken, or that the roof covering will be damaged.  In either case, you will have turned a “potential” problem into an actual emergency.

3.     Membrane roof.

Membrane roofs are an alternative to tar and gravel roof, and usually are found on slopes of 3:12 or less.  They are quite delicate, and are not designed to put up with any traffic on the surface.  Membrane roofs should be de-iced only by professional roofing companies that install this kind of product.  However, as with tar and gravel roofs, it is usually not necessary to get rid of the ice dams, as the covering (if properly installed) is designed to be water-tight.

4.     Other kinds of roofs

There are many kinds of materials used for roof covering, such as metal, aluminum, zinc, cedar shakes, clay tile, concrete tile, fiberglass panels, slate, and so on.  The ice-dam removal strategy changes with the type of roof covering, and with the underlying structure of the roof system.  It is usually best to refer this issue to companies that specialize in installing the type of roof covering you have, as they will know the potential dangers and weaknesses of this type of roof covering.

B.    Short-term preventive

Of course, the better strategy is to prevent a problem.  Assuming you have not fixed the underlying issues of insulation and ventilation (more on that in a later section), you can at least approach the problem with the goal of minimizing the problems that an ice dam can cause.

1.     Remove the snow

The simplest strategy is to remove the snow from the roof before it can melt and create an ice dam.  If the roof is not too high and not too steep, it is possible to do this using snow rakes (plastic scoops at the end of a very long aluminum pole), or getting onto the roof and using plastic snow shovels.  Of course, you need to do it immediately after each snow fall, because the melting/freezing starts as soon as there is some snow on the roof.

2.     Install de-icing cables

If the roof area is too dangerous to go onto, or too high, then removing the snow becomes impossible, and the second strategy can be used, which is to use de-icing cables or heating tape to melt channels into the forming ice dam.  This has to be done ahead of time, before the snow season starts.  This method CAN work, IF done properly.  However, most installations of de-icing cables do not accomplish their job and end up contributing to the problem.  So what are some of the common failures?

  • The gutters are not included in the de-icing strategy.  The meltwater then runs into the gutter, freezes, and backs up.  The cables need to be placed along the gutter, and down the downspouts.
  • The cables are placed horizontally and not vertically.  The point of melting channels in the snow is to allow the water to use these channels to run off the roof.  Therefore, they should be arranged more vertically than horizontally.  As well the cables should go into the gutter, to intersect the cables running along the gutter base – this way the water has an open channel to escape.
  • The cables are place too low, and the ice dam forms above the cables.
  • The cables are placed too far apart, and the space in between forms many small ice dams.
  • The cables are not secured properly, and snow movement causes them to come off the roof.

When using de-icing cables, you need to arrange them to provide for a water flow path from above the point where the ice dam can form, all the way down to the gutter, and down the downspout.  De-icing cables work, but they are an expensive band-aid.

C.     Fixing the causes

The best way to deal with ice dams is to make sure they don’t form in the first place.  If you’ve read the article “What’s an ‘Ice Dam’?”, you’ll know that the primary issue is that there is insufficient insulation which therefore allows heat loss to the attic, and with insufficient ventilation, the warm attic then melts the snow that accumulates on the roof.  The meltwater runs down the slope to the eaves, and once it is over the roof above the soffits, there is no more warmth to keep the water liquid, and it freezes.  To fix the problem at its source, you need to address both the insulation and the ventilation issues.

1.     Insulation

How much insulation is “good enough”?  The building code minimum depends on many factors, but the general recommendation is to have attic insulation between R40 and R60.  In our own work, we have observed that roofs with real insulation value of R30 or less almost always have serious ice damming issues.  Roofs with real insulation value of R40 or more almost never have ice dams.

Notice I wrote “real” insulation value.  The insulating value of various materials depends primarily on how much air they can hold without movement.  Still air is an excellent insulator.  Moving air, however, is not.  Therefore, to get the maximum value of insulation from any insulating material, it must be installed in a way that prevents movement of air through it.  It is not uncommon to find lots of insulation in an attic, but arranged in such a way that the effective value is less than half of what it should have been.

The insulation value also depends on the insulation being dry.  Wet insulation has effectively no insulating value.  Therefore, if one has had leaks in an attic due to ice dams, and those leaks soaked the insulation underneath, then the attic has even less ability to prevent heat transfer – enabling more heat to escape and melt more snow – a vicious cycle.

One very common source of heat in the attic, is the use of poorly installed and insulated pot lights or ceiling lights.  The boxes containing these lights are normally placed above the ceiling and displace a portion of the insulation that would have normally been there.  These lights generate a lot of heat, which then easily escapes into the attic (due to minimal insulation) where it is then transferred to the roof.

Different materials have differing insulating values.  To get R40+ insulation using fiberglass bats, would take about 13 inches if they were well installed with no air gaps between them, and no possibility of air movement through them.  If, the same bats were poorly installed, you’d need at least 26 inches to get R40.  The same R40 requirement can be achieved by 6” of polyurethane closed-cell foam.  Therefore in some areas of the attic where space is limited, it is worth thinking of mixing different types of insulation to achieve the goal of having at least R40 in the attic.

2.     Ventilation

Once the heat enters the attic, whether due to poor insulation or other cause, it will warm the air in the attic, which then rises to the roof decking, and warms the roof.  The effects of poor insulation can, to a certain extent, be reduced by good ventilation – that is, the movement of air from the soffits along the eaves to the outlets located near the top of the roof at the ridge.  In practice, we have observed that good ventilation reduces the effect of poor insulation, but does not completely prevent the heat transfer.  In addition, due to the complexities of construction of many homes, the ventilation air flow is not very linear and consistent, with many spaces that have no effective ventilation.

For passive ventilation to exist, it needs to enter the attic at a low point (typically the soffits), move through an air channel (minimum 2” according to the building code) into the attic, from where it exits through a ventilation outlet located hopefully near the top of the structure.

Some of the reasons why ventilation is NOT working include:

  • Blocked soffits (vented soffits installed over solid wood, vent holes in soffits covered by paint, insulation blown into the soffit cavities, etc.)
  • Insufficient air channel (insulation is too close to the roof to allow easy air entry from the soffit cavity into the attic).
  • Poor location of both intake and outflow vents, creating ventilation short-circuits,
  • Poor balancing of intake and outflow – too much or too little outlet or intake.
  • Internal attic obstructions that prevent the movement of air.

It is not enough to place a number of outlet vents and consider the ventilation issue to be “solved”.  There is a science behind this, and the amount of ventilation required can be calculated quite easily, if you know what you are doing.

D.    Preventing damage

If you cannot fix the problem at its source (namely by improving the insulation and the ventilation), then there are other things that you can do so that the ice dams don’t cause serious damage.

1.     Ice-and-water shield membrane

The most common solution is to install a width of ice-and-water shield membrane along the eaves, the valleys, the endwalls, and all other places where it can be expected that water from ice-dams could penetrate the roof covering.  For this protection to be effective, the right product needs to be installed in the right way, at the right time, and at the right place.  In another post (Dec. 8, 2013), I discussed some of these issues.

Ice-and-water shield membrane needs to be installed at the time the roof is being constructed, or at the time of re-roof.  It needs to be installed high enough up the slope to ensure that the worst ice dam will not breach the defenses.  It needs to be applied directly to wood, so that it can bond with the wood.  It needs to be properly overlapped to ensure proper sealing of membrane-membrane joints, and be properly primed if the membrane is contacting surfaces like metal or brick.  There are a few more “needs to” or “should” instructions, but it is clear that if not properly installed, the ‘miracle’ stuff won’t work when you really need it to work.  And yet,when we are asked to diagnose a roof failure this is where we find a large number of short-cuts taken .

2.     Ice belts

Ice belts are horizontal bands of smooth metal that are installed along the eaves (usually over the soffit cavities) to allow snow at the roof edges to slide off, and thereby removing one factor that can help the formation of the ice dam.  They work, kinda.  The real problem is that often times the belts are not high enough to ensure that no snow sticks to the roof and contributes to the ice dam formation, and under certain climatic conditions, the ice belt doesn’t prevent the snow from sticking to the roof.  However, being made of continuous metal with few joints, there is much less chance for water to enter through one of the joints.

Using an ice belt is a good way to reduce the chance of ice dams, but it doesn’t prevent them.  Again, an effective ice belt requires proper installation, proper waterproofing, and proper protection of the roof deck below the metal.

3.     Smooth metal roofs

Expanding on the idea of the ice belts, you can cover the entire roof with a smooth metal (in the form of panels or shingles), which will allow the snow to slide off the roof.  This is one reason why historically most roofs in the heavy snow regions usually have some kind of metal covering.  So why not install metal roofs everywhere?  There are several reasons why:

  • Metal roofs typically cost anywhere from double to as much as four times more than the common asphalt roofs.
  • Smooth metal roofs do shed the snow, but not always when you want the snow gone.  Under some circumstances the snow may stick to the roof, accumulate, and form a thick ice crust at the base of the snow, before finally conditions change and the entire mass avalanches off the roof slope.  Depending on where it ends up landing, you could have some serious damage or injury.  Therefore, smooth metal roofs need to be designed to allow snow descent in the right areas, and prevented from doing so in areas where injury or damage can be anticipated.  Not all contractors worry about these kind of niceties.
  • Smooth metals roofs have their own esthetic appearance.  Some love it, some don’t.
  • Metal roofs usually require a different level of expertise to install properly, compared to asphalt roofs.  These skills are not common, and are usually specific to the type and brand of material being installed.  Therefore finding good installers is somewhat more challenging.
  • Not every metal product is appropriate for every situation.  It requires some expertise to ensure that the strong points of a particular product are fully utilized for a specific installation, and that the corresponding weaknesses (and all products have weaknesses of one kind or another) have been adequately covered.

Metal roofs are an excellent roof covering, but they don’t make the ice dam problem go away.  There are many fewer opportunities for ice dams to form on a metal roof, but they still can happen.  And when they do happen, the other protective measures need to be in place.

E.     What NOT to do!

Having seen many attempts at removing ice dams, there are a few words of wisdom that come from such observations:

  • DO NOT put your de-icing solution on the snow or ice above the ice dam.  This will just enlarge the pool of water , and cause the water entering to be carrying the salt or chemical in the de-icing solution.  This can be very difficult to clean up after the ice dam is long gone.
  • DO NOT get on a ladder and start chopping away.  If the ice dam breaches, you will be on the receiving end of a lot of water, ice chunks and other stuff.
  • DO NOT try to do the de-icing by yourself.  This is pretty energetic work, and if you’re not used to this level of exertion, bad things can happen to your heart.  If something happens, who will find you, and when?  In addition, a ladder in the snow is not the most stable platform.  If you want to do the de-icing yourself, at least have someone at the bottom making sure that the ladder doesn’t move.
  • DO NOT try to work on the roof without using proper fall protection.  The falls aren’t the problem, it’s the rapid stop at the end.  Or, if you just tied a rope around your waist, you’ve created a situation where your spinal cord can be broken if you fall.  An ice dam is not worth becoming a paraplegic over.
  • DO NOT try to remove all the ice dam – some of the ice is between the shingles, and removing that little final coat of ice will also remove some of the shingles that are encased in that ice.

There are probably quite a few more that could be added to this list, but the point is – if you’re going to do either de-icing, or snow removal, do so in an intelligent, well-thought-out way, using the safe methods and the right tools.  Because your life may depend on it.   Or, hire people who know what they are doing.  Like us.

(c) 2013 Paul Grizenko

F.     Links:

CMHC article on insulating your home:

Jon Eakes article on insulation levels:

Definition of R-value:

Natural Resources Canada publication: 2012 Energy Start for New Homes Standard:

G.    Request for feedback

If you have found this information useful, let me know via a comment.  If you found the information inaccurate or misleading or simply not correct, please contact me to let me know why you think so.  If you have experienced an ice dam and had it resolved, how did you do it?  I’d love to read your comments.

Waterproofing membranes for roofs – Miracle product or junk?

The last time you had your roof done, you wanted to be sure that the leaks you had before would never happen again, and you made sure that your roofer installed waterproofing membrane to protect your roof.  Now it’s winter, and you’re having some leakage issues.  WHY?

Let’s start by examining what are waterproofing membranes, and how are they should be used.

There are a number of products that are marketed as waterproofing membranes for sloped roofs.  There are different grades, performances and price-points.  For the membranes to work properly, they need to be properly installed, under the right conditions, at the right place(s) and for the right purpose.  As is true for all building materials, they have both strengths and weaknesses, which must be taken into account by the installers.  From their method of application, they are also known as “peel-and-stick” membranes.

In general the membranes work by bonding (melting into) the wood decking, and thereby providing a waterproofing bitumen layer which keeps the water out.  The membranes bond well to each other, and to wood (provided it is dry and warm enough).  When pierced by a fastener such as a nail, the material acts as a gasket around the nail and resists water penetration.  Therefore, if the membrane is applied to the right place, in the correct way, at the right temperature, and to the right materials, it works.

Membranes, however, sometimes fail.  It is useful to know the different ways failure can happen.

  • The membrane was not installed over dry, solid wood.  This meant that the membrane could not bond to the wood, and thereby establish a waterproofing layer.
  • The membrane was installed over non-wood materials.  This is a common failure, found when the installer did not properly prime the non-wood surface to ensure both adhesion of the membrane and the creation of a waterproof seal.
  • The membrane was not overlapped sufficiently.  Each membrane has a minimum overlap requirement, and the installers MUST ensure that the bond between successive layers is active.  This kind of failure also happens if the membrane was laid vertically when it should have been laid horizontally.  The vertical joints are more susceptible to leakage.
  • The membrane was cut flush with the edge of the roof.  This is a common installation failure, which allows the water that may be on the surface of the membrane to enter the decking at the edge of the roof.  Proper installation practice is to run the membrane past the roof edges by at least 1-2 inches to ensure the water stays outside the roof system.
  • The membrane was installed over damaged wood or on a joint.  Fasteners piercing the membrane at those points will not have the solid wood support that ensures the dimensional stability of the puncture point, and therefore, water will enter the roof system through the nail holes in those locations.
  • The membrane was installed over a non-ventilated space.  This may become a very serious issue if the space is NOT sealed, and may contain moisture or water vapour.  This is known as “trapping” the moisture, and will lead to both wood rot and mold (potentially toxic) in the spaces.
  • The membrane cracked or torn, letting in water.  This can happen if the membrane was left exposed to the sun for longer than the manufacturer recommended, or if there was movement in the structure that put tension on the membrane.  This can also happen more easily with cheaper membranes.
  • The wrong kind of primer was used, leading the materials to “melt” the membrane, instead of providing a suitable attachment point.

There are, of course, many more ways the membranes can fail to work, but as can be seen above, if a membrane doesn’t work, it’s almost always because the installer failed to do the installation properly.  Proper application of the membrane takes time, and ensuring that the overlaps are all properly sealed, and that the junctions to various roof penetrations are properly primed and joined, is detail work that cannot be rushed.  As well, as in painting, if the proper preparation is not done, then the adhesion of the waterproofing layer is going to be compromised.

In our experience, the failure of the waterproofing layers is a very common reason for replacing a roof prematurely.  Unfortunately, once the roof covering is on, it’s impossible to verify whether this critical element was properly installed.  In practice, if the cause of a roofing failure is suspected to be linked to the membrane, it is often necessary to disassemble the roof system and to do an “autopsy” to determine the cause of the failure.

So, how do you ensure that the waterproofing step is properly done?  There are a number of steps that help you get to the desired result.

  • Check the products that will be used.  Get the brand names, the product names, and the installation specifications.  Read carefully the parts about what NOT to do.  Make sure that the manufacturer’s suggested use covers what you want to use it for.
  • If you’re having someone else install the products (your roofer, for instance), ask them to explain where they would use the products, what kind of preparation they will do, what kind of verification or quality control they will do to ensure the materials will work as intended.  Ideally, they should be able to show photographs of prior installations where they did the membrane application.  Probably more important, is asking them under which circumstances the products did NOT work, and what they would do if those circumstances were found on your roof.
  • Once the installation starts, you need to check how the material is being installed.  How well was the roof preparation carried out?  Are the non-wood surfaces being primed with the appropriate primer?  How are the overlaps sealed?  Is the edge of the roof being overlapped?  Imagine water running on the surface.  Where will it go?  Is there a chance for obstruction?  Is there any apparent damage to the material during the course of installation?
  • Once the installation is complete, but before the covering or flashing is put over the membrane, the surface needs to be verified as to its adhesion, overlap, and coverage.  It is a good idea to request (in the contract) that photographs be taken of all roof penetrations, roof joins (such as valleys, endwalls, sidewalls), and roof terminations (rake or gable end, eave, hip, ridge) to show how those details were executed.  Alternatively, hiring a third party to conduct an inspection at this stage is another way to ensure that this critical step in the process is properly done.
  • Occasionally, especially with complicated roof lines and assemblies, it is appropriate to conduct a water test to ensure that there are no weak spots in the water-proofing coverage.
  • If membrane will be installed over the entire roof, it is really, really important to ensure that EITHER the roof system below the membrane is sealed and impermeable to water vapour, OR that it is well vented, so that any moisture trapped under the membrane can escape.  If a roofer or contractor agrees to install the membrane over the entire roof without make sure that either condition exists to a satisfactory level, they are being at best ignorant, and at worst, willfully negligent.

Of course, the membrane protection is only part of a well-constructed roof system.  Good installers will build in several layers of over-lapping protection to ensure that there is no single point of weakness that can undermine the efforts put into building the roof system.  If you’re not sure what needs to be done with your roof, give us a call.  We can give you an intelligent analysis of what issues are important in your situation, and what you need to do to make sure your system works.

(c) 2013 Paul Grizenko


Below are two membranes that we use routinely, and that have been, in our experience, proven to work well, provided they are used correctly.

Grace Ice and Water Shield Membrane:

Interwrap – Titanium PSU membrane:

Further information:

If you are interested in knowing more, use the contact form (under the Contact Us menu selection), or give us a call at 514-636-2300.