Stripping is a good thing. Really.

Roof stripping, that is.  This is the process of getting rid of the old roof covering material, down to the deck.  In the process, if done correctly, you’ll learn a lot of things about what worked on your roof and what didn’t.  As all things that are good for you, there are costs and inconveniences involved, aspects which are exploited by those contractors who don’t have your best interests at heart.

What are some of the typical reasons you’re given why leaving your old roof on and going over is/are acceptable?  They include:

  • You’re saving money.
  • It’s more ecological (no landfill waste!).
  • It’s more secure.
  • It provides another layer of protection to your roof.
  • It’s recommended by the manufacturer.
  • There’s much less residual mess to clean up.

So many great reasons why you should just leave the old roof on, and go over!  And yet, pretty much all of these are false, based on the homeowner’s lack of knowledge of how the roof system is supposed to work, and compounded by the contractor’s desire to get the job done as fast as possible, get paid, and move on.  If you are presented with the suggestion that leaving your old roof on is an acceptable strategy, there are a number of things you should be aware of before you agree to this.

The real reasons why not stripping your roof is really good for your contractor (but not for you).

1.  Lower cost of sale.

Since there are many roofers competing for your business, the temptation to cut corners in order to lower the price is always present.  Eliminating the cost of stripping can reduce the overall cost of the job by anywhere from $1,000 to $5,000 (depending on the size and complexity of the roof).  This is because the cost of stripping include:

  • Refuse container rental
  • Debris disposal fees
  • Cost of labour to remove the old roof covering
  • Cost of labour to clean up the stripping debris from around the property
  • Loss of time for work crew if the stripping uncovers problems that need repair (which means the problems must be diagnosed and estimated, the client has to be contacted to approve the extra work, repair materials have to be purchased and brought to the work site, and repair work has to be done)
  • More expensive materials needed for proper waterproofing IF the roof is stripped

The manufacturers of roofing products will say that going over an existing roof is an acceptable practice, to allow them to compete with other manufacturers for the contractors’ business.  Of course, to limit their liability, they also have a rather long list of conditions that have to be met by the contractors in order that the resulting roof system is acceptable.  But of course they are not then responsible if the contractors (wink, wink, nudge, nudge) don’t fulfill these conditions.  Their objective is to sell as much product as possible.

2.  Faster turnaround.

Roofing is a business where doing the most amount of jobs in the shortest period of time is the goal.  The ideal work model for most roofing contractors is to show up at a client site, do the minimum of preparation, install the product, and leave.  This can be done in as little as two days for metal systems.

Discovering problems, diagnosing the issues with the roof system, dealing with issues such as insulation, ventilation, and roof design issues, are all things that slow down this process, and create additional headaches for the contractor.  Resolving such “found” problems requires additional skill-sets that the installation crew focused on a fast install usually will not have.  It also requires the foreman on site to communicate with the owners, and determine the best way to fix the problems, and many foremen just do not have the communication skills to properly explain what the issues are, and what the recommended solution can or should be.  Also, usually the owners are not around, having gone to work, and getting in touch with them to discuss these issues completely slows down the process.  So, many contractors prefer NOT to deal with these issues, but just plow on ahead.  Not stripping the roof, allows them to ignore problems that otherwise would have to be fixed.

3.  Cheaper work crews.

The skill set involved in installing a product or system is non-trivial, but it is not as extensive as the skill set required to diagnose and repair a wide variety of potential roofing problems.  The tools (and supplies) required to fix problems represent additional investment that the contractors have to make IF they are going to do a proper job.  Both the additional skill set AND the extra tooling represent work crew costs that can be avoided if stripping and roof repair isn’t part of the work scope.

Another aspect to the installation of roofing is that often a contractor will hire a subcontractor to carry out the actual installation and almost always the business arrangement is that the subcontractor is paid a fixed amount.  This gives the subcontractor little incentive to find and fix problems found, as they will almost never be paid for additional labour needed to fix such problems.  Since the subcontractor has no contractual obligation to the homeowners, any problems found are usually ignored and covered up.

What are the consequences to you, the homeowner?

1.  Roof system issues are ignored.

If the roof is not stripped, then any deterioration of the roof, due to leakage or other cause, is left to continue causing problems, potentially undermining the integrity of the roof, and shortening its expected life-span and performance.  These include issues such as rotting or delaminated sheathing, broken planks or decking, compromised rafters and joists, deteriorated fascia, and compromised insulation.

2.  Building Code violations.

In most jurisdictions, there are restrictions on how many layers are allowed on a roof before it MUST be stripped, and usually these are a maximum of two layers of asphalt shingles (or equivalent).  Municipalities can require the homeowners to remedy the code violation if they become aware of this.  Furthermore, if the property is up for sale, a careful home inspector may flag this as a potential problem which will at least lower the value of the property.

3.  Potential fire issues.

Multiple roof layers are a serious problem for firefighters if there is a fire and they are trying to vent the roof to reduce the flammable gasses.

4.  Additional weight.

Each layer of asphalt shingles weighs 2-3 lbs. per sq.ft., and keeping that weight on a roof puts a stress on the structure.  This may not be an issue if the house was overbuilt, but we’ve seen joist and rafter sagging and other effects (cracking of gyproc on stressed walls, difficulty opening or closing doors and windows) when we came across roofs with excess weight.

5.  Poor waterproofing.

Going over an existing roof means nailing the new product over the existing material, creating holes that the material was not designed to have.  Furthermore, most waterproofing membranes requires adhesion to continuous solid, clean, and dry wood to be effective, which means that in practice there is no real waterproofing present on roofs where the old roof is retained.  The common practice of overlaying the existing roofing by synthetic underlayment does not protect the roof from water penetration since the underlayments are NOT membranes.

By definition and design, all steep-slope roofing materials are designed to shed water, but not be waterproof.  This means that on any steep-slope roof, one can expect the water to penetrate the roof covering.  This places the burden of keeping the water out of the roof system onto the waterproofing system installed under the roof covering.  In reality, the underlayments and membranes and other waterproofing (roofing cements, sealants, and flashings) are the true waterproof layer that keeps the water out, and the outside covering is for the most part, a cosmetic cover.

Many contractors rely on caulking to be the waterproofing method, since it is easy to do and is visible.  However, caulking exposed to the sun will lose its elasticity in as little as five years, and can be expected to pull away from the substrate, allowing water entry.  Therefore, if the caulked joints are not further protected on the underside by proper waterproofing, these joints will be potential sources of leakage.  These leakages will start as intermittent seeps which enter the roof system, and the old roofing material tends to act like a sponge absorbing these seeps.  If the attic ventilation is inadequate, then these seeps will increase the moisture content of the roof deck and provide good conditions for wood rot and mold.

6.  Poor installation.

It should be clear that if the contractor is not interested in doing a good job (proper preparation, discovery of hidden problems, ensuring that the roof as a system is working properly), then that attitude will extend to the quality of the installation.  Ensuring that the many details are properly done takes time, skill, and care.  Contractors who are in a hurry don’t usually spend a lot of time on these details, so while the product superficially appears to be well-installed, the real cost of a hurried installation is only found later.  However, it usually takes a weather event (strong winds, heavy rain, or similar condition) to reveal the weakness in the installed roof system.

7.  Poor performance of the roofing system.

Keeping in mind that the roof covering is only one part of the overall roof system, it should be clear that any change of the roof covering that does not also take into account how that covering interacts with the roof system is at best not taking advantage of improving the roof system performance, and at worse, compromising it.

If you have read some of my other posts in this blog, you’ll have noted that the roof system comprises the following elements:

  • Vapour barrier
  • Air barrier
  • Insulation
  • Ventilation
  • Roof structural elements (rafters, joists)
  • Decking
  • Waterproofing
  • Roof penetrations
  • Underlayments and membranes
  • Flashings
  • Roof covering

Changing the roof covering without considering how this change will affect the rest of the system is asking for trouble.  Unfortunately too many contractors have little interest in understanding the functioning of the existing roof and thinking through how the change of roof covering will affect the roof system.  For instance, one of the key elements of understanding the existing roof system is a proper inspection, including both inspections of the outside (by walking or accessing the roof surface), and inside from the attic.  These inspections reveal how the existing roof is functioning, and allows a good roofer to understand what aspects need improvement or additional work.  If these inspections have not been done, then it is a clear sign that the contractor (or salesman) has little interest in helping a homeowner improve their situation.

The fallacies of the marketing/sales claims.

1.  You’re saving money.

Up front, the cost is less, but at the expense of dealing with issues which will be much more expensive to fix later on.

2.  It’s more ecological (no landfill waste!).

So now the “landfill” is sitting on top of your house.  The material continues to deteriorate since the heat cycle continues, and oxidation of the organic materials in the old roofing also continues.  The result is that you have a nice-looking roof installed over material which will provide less and less support over time.

3.  It’s more secure.

This usually refers to the reality that the roof is covered at all times against unanticipated rain showers.  Of course, if the contractor knows his trade, this will also happen even if the roof is stripped, because good contractors know how to protect their client’s homes, by phasing the stripping and installing waterproofing as they go.

4.  It provides another layer of protection to your roof.

If you think about it even for a short while, it should be obvious that this claim is false.  The existing roof covering was not designed to be waterproof with multiple penetrations through its surface by fasteners which will anchor the upper roof material.

5.  It’s recommended by the manufacturer.

As noted earlier, it’s a concession by manufacturers to avoid losing sales, and is usually accompanied by a long list of requirements to ensure that doing this does not compromise the integrity of the installation.  So the contractor’s statement that this is “recommended” is at best a mis-representation that this is an allowed practice, but it certainly does not represent the “best practice”.

6.  There’s much less residual mess to clean up.

While this is certainly true, it also speaks to the quality of the installation crew.  A good crew will do an excellent job of protecting the premises and cleaning up each and every day they are on site.

Summary:  in the long run it’s much more expensive to do the expedient thing, and avoid dealing with the issues.

You’re going to be paying for this “saving” in ways that won’t be obvious immediately, and the cost will be much more than the initial amount you’re “saving”.

If you have quotes for roofing or re-roofing that feature these “savings”, you may wish to get some expert opinion on whether these “savings” are real.  That’s why calling me for a consultation will potentially save you much more money and grief over the long haul.


(c) 2017 Paul Grizenko


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