Oftentimes, going over is a cheaper choice than tearing down and replacing your entire roof. That’s what many London ON homeowners believe when it comes to replacing their roofs. However, is it actually a good an idea as it sounds? The truth is: it depends greatly whether you can accept some of the flaws and problematic areas it has.

Asphalt shingle roofs are an affordable investment especially for new homeowners who have invested so much in labor and materials for home construction. In addition, it introduces the traditional residential look that most homeowners want for their house. However, tearing them off is time-consuming — which means higher labor costs.

Going over the asphalt shingle roof with a metal replacement is quite a viable roofing solution. Roofing contractor Gertrude Webster pointed out the following advantages of installing metal roof over asphalt shingles:

Some metal roofing contractors are trying to convince people that you do not need roof wrap under metal roofing — presumably so they can get their initial installed cost more competitive with other roofing materials. Don’t fall for that — metal roofs do leak at times, and without the roof wrap you have nothing to keep the water from saturating and rotting the sheathing and rafters, destroying your entire roof.

Also, if your roofing is flat sheet raised seam (flat panels except with bulges up for the seams) rather than corrugated, the batts or nailing strips (though roofing is not fastened with nails) should be discontinuous — small gaps are needed every few feet to allow hot air to flow up to the ridge vent (which you should definitely have installed), otherwise it just becomes an oven between the roofing and the sheathing, plus the sheathing gets much hotter and makes your entire attic hotter in the summer.

Lastly, It saves having to fill up landfills with old shingles. (Continued)

Some Precautions

As responsible and reliable London ON residential metal roofing contractors, we won’t be sharing DIY instruction on installing metal roofing. However, we will tell you about some precautions even professional roofers will brief you about installing metal roofing over shingles.

Metal Roofing Source has a great set that you can read. Learn more about it below:

When you decide to go ahead with this project there are a couple of precautions regarding the underlying material:

If there are any existing roof leaks, you need to address them and replace any rotten sheeting or rafters.

If there are any signs of problems caused from the previous roofing weighing too much, they must also be addressed.

This could include things like sagging decking or buckling trusses.

A couple of options:

A layer of underlayment installed on top of the existing shingles will help keep the granules of the old shingles from rubbing against the back of the metal and causing possible corrosion.

The industry standard for underlayment is often thought of as felt paper (tar paper) but there are also many newer synthetic underlayments that are designed to work well with metal roofing. Standard tar paper has a tendency to stick to the back of metal roofing.  This can cause the paper to tear when the metal roofing expands or contracts as it is designed to do.  The new synthetic underlayments do not have this problem as their design far exceeds the felt paper standards. (Continued)

Some Problems You Might Face

As always, no roofing material or procedure is ever perfect. What makes it perfect is the London ON homeowner’s acceptance of these limitations and preparing for such an eventuality in the future.

Metal Roof Network has a great list of pros and cons when it comes to installing metal roofing over shingles for the following year:

Ideally a metal tile, shake or shingle roof should only be installed over one or, at most, two layers of existing roofing, and providing that the existing roof framing and decking is in good condition. A good way to determine “good condition” is to walk around on the roof you’re considering covering to look for soft spots or evidence of weak, rotten, or compromised structural components. If there’s any question about the integrity of such components, then removal should become an instant high priority. If the roof appears to be straight and solid, and there is no evidence of persistent leaks inside, then it’s probably a good candidate for an over-top application.

Assuming there are no apparent problems after such an inspection, then the other thing to do is have a look at the planes of the roof from the ground. If they all appear to be straight and true, then it’s likely the structure beneath is sound. If visible “bellies” or depressions in the roof can be seen, then there’s reason to investigate the structural components of the roof to make sure there aren’t broken or overloaded rafters or trusses.

Also, be sure to keep in mind that adding another layer of roof covering will raise the depth of the total roof covering. This may impact things like skylights, roof-to-wall flashings, dormers, roof-top HVAC equipment and other adjoining details. The extra height of the new roof assembly has to be considered in advance in order to avoid potential problems in these regards. (Continued)

Use Only The Best Roofers In Your Area

All metal roofing installations over asphalt shingle roofs require the most precise hands and experienced professionals in London ON. If you haven’t found one yet, you can work with us at Cub Roofing for all your needs. Contact us today to learn more about the top quality of metal roofing installations we can do for you!