How many layers of shingles are allowed? You ask. At this point, a homeowner’s roof has reached the end of it’s lifespan and is due for a re roofing, gathered estimates from multiple contractors and aren’t sure why layering shingles is more affordable.
Where 2 layers are recommended, up to 3 layers at a maximum depending on the area’s regulations (or building and city codes), and in some rare cases 4 layers from experience. Sometimes it’s asphalt shingles layered on top of old cedar shakes, asphalt shingles, concrete tiles, etc. These are all possible to layer, if you choose to.
Generally, 2 layers of shingles should be the max if you choose to, never reaching 3 layers or more for your roof’s and home’s safety. Once the 2nd layer has reached the end of its lifespan, a tear-off and new shingle installation would be the best course of action.
Although, Roofing Mission (a.k.a our “BulletpRoofers”) will always recommend “1 Layer Max” because layering shingles is a short-term fix will result in long-term pain for the homeowner every time. Here are 64 reasons not to put shingles on top of shingles or layer shingles to help explain why we believe this to be so. Which is especially true for those that live in areas that have heavy rainfall, regular storm-events, hail, etc. like the Lower Mainland will regret the decision some day.
Instead we always recommend tearing off the old shingles, repairing the roof deck and installing new shingles, as you will learn why shortly. Ensuring the longevity of a home’s roof and properly protecting the home at the same time.
As explained in:
- Are two layers of shingles better than one?;
- Are three layers of shingles better than one?;
- Are four layers of shingles better than one?.
To provide insight into the situation, we’ll cover a few areas to help you understand layering roofing shingles in more detail.
Table of Contents
- Requirements to Layer Roofing Shingles
- Pros & Cons of Layering Roofing Shingles
- Conclusions about Layering Roofing Shingles
Requirements to Layer Roofing Shingles
These requirements are what some roofers who cut corners are looking for in order to pitch a homeowner on a cheaper option of re roofing, to layer roofing shingles.
The following 4 requirements need to be met to layer roofing shingles:
- End of a Roof’s Lifespan; Its asphalt shingles have signs or buckling, blistering, curling, missing granules, broken or missing shingles, and/or leaks or excess moisture in the attic, etc.; Normally due to aging, wear and tear, and the environment a home is located in. Except the roof shingles are relatively flat regardless of this damage.
- Roof is a 4:12 Pitch; This means a roof’s slope is relatively flat (not steep), technically it is a 4” rise to a 12” run. Identifying the roof as a quick job for a roofer, literally lay new shingles and leave for them.
- Existing Flashing is in “Good Shape”; From a surface assessment, the metal pieces protecting joints between the roof deck and roof protrusions (air vents, chimneys, plumbing, etc.) will trust the previous installer did a decent job. Flashings protect sensitive areas that are prone to leaks, take it into consideration. The less roof protrusions, the better it is for a roofer to layer shingles in these cases.
- Homeowner’s Budget is Small; In order to secure the job, a roofer will suggest layering shingles at a lower quote, an average of $1,000 less in cost savings for the homeowner. This is a result of skipping the critical tear-off step in order to reduce labor costs, material costs and disposal costs for the roofer allowing them to pass the savings to the homeowner. Without tearing off the old shingles to expose the roof deck, any damaged roof decking and flashings will be left to worsen over time.
Although a roof meets these requirements, it’s important to understand that:
- A roofer’s lower quote is based on very little going wrong. If at any point the roof decking breaks or becomes damaged while laying new shingles on top of the old shingles, this will immediately add to the quoted cost; Adding costs to tear off old shingles, replace or repair the roof decking and then installing new shingles on top.
- Highly recommended a homeowner shouldn’t attempt layering shingles themselves, repairing the roof themselves. If roof decking breaks, it can result in serious injuries and major damage to the roof because the homeowner isn’t using specialized safety equipment.
Pros & Cons of Layering Roofing Shingles
We’ve outlined the pros and cons to aid in the homeowner’s decision to layer new roof shingles over the old shingles. At a glance, the cons outweigh the pros heavily and warrant the homeowner’s attention to better understand “why” we would recommend not layering shingles in the first place. Reason being it prevents the anatomy of a roof and each roofing layer‘s individual functions that together allows a roof system to work properly.
As a guideline, any roofing practice that helps water to accumulate on the roof will result in leaks one day.
Pros of Layering Roofing Shingles
The pros of layering roofing shingles help the roofer to sell their service to the homeowner:
- Cheaper, faster and less messy; A roofer can pass the cost savings of skipping the time intensive tear-off step and disposal of old shingles to the homeowner; Depending on the size of the roof, this can potentially shave off a day of work for the roofer.
Cons of Layering Roofing Shingles
The cons of layering roofing shingles show how layering roofing shingles is a short-term fix at best, and will result in long-term problems that could be expensive.
- Multiple layers of shingles traps heat between shingles, instead of insulating and moderating its temperature like it should. This trapped heat promotes condensation under the shingles, together reducing the new shingle layer’s life in half.
- Each Layer adds Weight, it’s like adding a second or third roof; For example, an average 30 square foot roof requires 90 bundles of shingles. Each bundle weighs about 100 lbs, adding roughly 9,000 lbs of additional weight for each layer. It’s concerning as most residential homes can’t handle this weight; Additional stress on the roof from heavy rainfall or snowfall could cause the roof deck to cave-in.
- Roof becomes Bumpy and Aesthetically Displeasing; Installing new shingles over old buckled or warped shingles will make a roof lose its curb appeal, uneven and bumpy. If the new shingles are of a different size like 3-tab shingles are 5” and architectural shingles are 5 ⅝”, this will result in bumps every 8 shingles. These bumps allow water and wind to get underneath the new shingles, eventually causing leaks.
- Difficult to Locate and Repair Roof Leaks; Finding the source of a roof leak becomes difficult because each layer of shingles can carry water to different parts of the roof before entering the home. Making it difficult to know which one is causing the actual leak, and where else the water is damaging the home. Once located, it will require an expensive repair because it will involve tearing off the old shingles, repairing the roof deck and installing new shingles; There are many risks of putting off repairs on a leaky roof and risks of neglecting your roof maintenance.
- No Opportunity to Fix the Roof Deck; This ignores any damaged roof decking, flashing, and ice and water barriers that need repairs due to not tearing off the old shingles and exposing the roof deck. Allowing any existing leaks or water damage to continue happening without the roofer and the homeowner knowing, until it becomes a real problem for the homeowner.
- Disqualifies Manufacturer’s Warranty on New Shingles; Disqualifies material warranty, pro rated enhanced warranty and contractor’s workmanship warranty. For example, 3-tab asphalt shingles come with a 25 year warranty, architectural 30 year warranty that’s pro rated 10 years after coverage ends. Further, if a roofer uses all components from one manufacturer the homeowner receives a 50 year non pro rated warranty and contractor’s workmanship warranty.
- Disqualifies Insurance Coverage for Damages; Depending on the provider, any layering of shingles will not be paid for by the insurance company. Reason being, there is an additional cost of labor to tear off each layer of shingles and replace each layer of shingles.
- Lowers Home’s Value when Selling; During home inspections, multiple layers of shingles on the roof is a red flag (negative) on their assessment of the home’s value because it indicates potential problems for the new homeowner.
Conclusions about Layering Roofing Shingles
Depending on the region a homeowner is located, the number of acceptable layers of shingles may be different but an average of 2 layers of shingles are generally acceptable, except it isn’t one of the ways to make your roof last longer or how to extend the life of roof shingles unfortunately.
From our experience, a homeowner should do their own research especially when roofing contractors are quoting below the industry standard. It should raise some red flags as they are trying to win a contract from the homeowner by cutting corners to make it possible.
Any homeowner who is unsure as to how to navigate roofing themselves or require additional information should always consult a professional roofer. Especially, when it’s possible to avoid a hasty repair at the expense of one’s own safety.