Can I Install Shingles Over shingles?

Aug 23, 2021Education, Knowledge Centre

When it comes to any project, there is always a way that you can save a buck. Reroofing over your old shingles is one of them. There are a lot of articles and how-to videos going over how to do the process for doing a reroofing over existing shingles. Professionals also use to do it all the time. So then, based on this information, you should just layer shingles on. Right?

No.

Well, why then?

It comes down to specific factors.

Kicking the Can Down the Road.

If you are thinking of reroofing over existing shingles, the most likely reason is that you want to save money on the tear-off for the existing roof. So you go ahead and get a new roof done over on top of the existing shingles. Maybe all you want is a different colour. However, even if the roof was in excellent condition underneath, you need to rip the original shingles when it comes time to replace the top layer anyway. So, in the end, you’re not saving money but just kicking the can down the road 20 years (if the reroof even lasts that long) and having to spend the money anyway!

In a perfect world, all you will do is defer payment to a later date; unfortunately, more issues can arise when reroofing shingles over shingles, especially if done more than once.

Cost more later
Cost more later

Kicking the Can Down the Road.

If you are thinking of reroofing over existing shingles, the most likely reason is that you want to save money on the tear-off for the existing roof. So you go ahead and get a new roof done over on top of the existing shingles. Maybe all you want is a different colour. However, even if the roof was in excellent condition underneath, you need to rip the original shingles when it comes time to replace the top layer anyway. So, in the end, you’re not saving money but just kicking the can down the road 20 years (if the reroof even lasts that long) and having to spend the money anyway!

In a perfect world, all you will do is defer payment to a later date; unfortunately, more issues can arise when reroofing shingles over shingles, especially if done more than once.

The Main Roofing Problems with Shingles Over Shingles.

Uneven Surfaces

A nice flat surface is ideal for a sound installation of shingles; however, pre-existing shingles make a surface that can be bumpy, which causes a host of issues.

  • Firstly, when you put shingles on top, one of the first things you introduce is more stress due to the uneven surface causing the shingles to be more prone to breaking and cracking before they reach the end of their lifespan.
  • Secondly, securing the shingles becomes more challenging due to the added thickness of the roof, as the nails are not long enough to provide a proper attachment to the surface. This issue increases with each subsequent layer.

Increased Weight

Adding an extra layer of roofing materials adds more weight, consequently straining the roofing system. In Alberta, we also have frequent snowfall in the winter, and the excess weight from the snow will test the limits of the structure. The increased weight problem is also more of a factor for smaller roofs not designed for the additional weight in the first place.

Warranty/Insurance

When re-roofing over top of existing shingles, you may be voiding your warranty and may not have adequate insurance protection on your entire roofing system. Sometimes it is covered, but more and more warranties and insurance policies don’t cover multilayered shingled roofs. So always check with your insurance and roofing provider first for accurate information.

Underlayment and leak protection

Let us start by saying that there are ways to seal over the top of an existing roof properly, but they are not the best. Our location exacerbates this issue due to the need for proper water and ice leak barriers under the older shingles for our harsh winters.

Selling you home and problems

Selling your home

When you sell your home, you might think shingles on top of shingles are the best thing to do as you don’t need to worry about the tear down later on. However, home inspectors and roofing inspectors will report this to the potential buyer and thus make the value of your home go down. It’s also one of the things where if the homeowner was not willing to do the job correctly the first time, other parts of the home could have had the same treatment. Keep in mind that the homeowner could not have had knowledge or maybe was even advised just to layer it on top, so don’t always jump to a conclusion, just food for thought.

What if You Have A Multiple Shingle Layered Roof?

Get a roof inspection as it could be fine in the best-case scenario, but you might need to add the extra cost for a two-layer tear-off when your next roof is required. On the flip side, you could have severe problems with the roof’s foundation and other issues from the abovementioned sources. If it’s more than two layers, you need to get it checked out a lot sooner, as those same issues with leaking, moisture, ventilation, and wood rot can be more costly to fix if going untreated.

Contact us for a roofing inspection to have that peace of mind for your home.

Pin It on Pinterest

Share This