{"id":4956,"date":"2026-11-09T09:16:10","date_gmt":"2026-11-09T13:16:10","guid":{"rendered":"https:\/\/metalroofcanada.ca\/?p=4956"},"modified":"2026-11-09T12:22:24","modified_gmt":"2026-11-09T16:22:24","slug":"metal-roof-over-shingles","status":"publish","type":"post","link":"https:\/\/metalroofcanada.ca\/en\/metal-roof-over-shingles\/","title":{"rendered":"Can you install a metal roof over existing shingles?"},"content":{"rendered":"<div data-elementor-type=\"wp-post\" data-elementor-id=\"4956\" class=\"elementor elementor-4956\">\n\t\t\t\t<div class=\"elementor-element elementor-element-7e3c376 e-flex e-con-boxed wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-parent\" data-id=\"7e3c376\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t<div class=\"elementor-element elementor-element-7141556 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"7141556\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-b1289f0 elementor-widget elementor-widget-text-editor\" data-id=\"b1289f0\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Installing a metal roof over existing shingles is a question many homeowners ask their roofer. The idea is appealing: avoid removing the old shingles, save on labour and shorten the timeline. Indeed, it\u2019s technically possible in some cases. However, it isn\u2019t always the best option.<\/span><\/p><p><span style=\"font-weight: 400;\">In this article, we explain when this approach works, when it causes problems and why most specialized roofers recommend complete removal instead. You\u2019ll thus have all the information you need to make the right decision.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-92c9697 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"92c9697\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-a3045d4 elementor-widget elementor-widget-heading\" data-id=\"a3045d4\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">How it works in practice\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d9f43df elementor-widget elementor-widget-text-editor\" data-id=\"d9f43df\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">The principle is simple. Rather than removing the worn shingles, the contractor installs a system of battens or furring strips over them. These battens create a flat, even surface to which the metal panels are then fastened. The old shingles therefore remain in place under the new roof covering.<\/span><\/p><p><span style=\"font-weight: 400;\">This method gained renewed popularity after the 1998 ice storm in Quebec. Insurance companies at the time paid for metal roofs to be installed directly over damaged shingles. It was then the fastest solution to protect thousands of homes.<\/span><\/p><p><span style=\"font-weight: 400;\">Today, some contractors still offer this option. Indeed, it can save a few thousand dollars on the cost of removing and disposing of the old shingles. However, this short-term saving hides risks that every homeowner should know about before saying yes.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-61ed31c e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"61ed31c\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-3ab22e7 elementor-widget elementor-widget-heading\" data-id=\"3ab22e7\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">The advantages of leaving the shingles in place\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-0510607 elementor-widget elementor-widget-text-editor\" data-id=\"0510607\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Installing a metal roof over existing shingles has some real advantages. That\u2019s why this option comes up so often in discussions.<\/span><\/p><ul><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Savings on removal:<\/b><span style=\"font-weight: 400;\"> removing the old shingles costs between $1 and $3 per square foot in labour and disposal fees. On a 1,200-square-foot home, that therefore represents between $1,200 and $3,600 in savings.<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Less waste:<\/b><span style=\"font-weight: 400;\"> the old shingles don\u2019t end up in the landfill. This is a concrete environmental benefit, especially since shingles are<\/span><a href=\"https:\/\/www.recyc-quebec.gouv.qc.ca\/sites\/default\/files\/documents\/etude-mise-en-marche-et-gestion-toitures.pdf\"> <span style=\"font-weight: 400;\">practically never recycled in Quebec<\/span><\/a><span style=\"font-weight: 400;\">.<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Faster job:<\/b><span style=\"font-weight: 400;\"> without removal, the work moves faster. Your home is thus exposed to the elements for less time during the transition.<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Extra layer:<\/b><span style=\"font-weight: 400;\"> the old shingles add a protective membrane between the deck and the metal panels.<\/span><\/li><\/ul><p>\u00a0<\/p><p><span style=\"font-weight: 400;\">These advantages are real, but they only tell part of the story. The associated risks deserve just as much attention.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-053ab61 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"053ab61\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t<div class=\"elementor-element elementor-element-7a90fc7 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"7a90fc7\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-c9d5a74 elementor-widget elementor-widget-heading\" data-id=\"c9d5a74\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">The risks to understand\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-c2dc8d0 elementor-widget elementor-widget-text-editor\" data-id=\"c2dc8d0\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Most specialized metal roofers advise against installing over existing shingles. Their reasons are concrete and based on years of experience in Quebec.<\/span><\/p><p><span style=\"font-weight: 400;\">The first risk is the inability to inspect the deck. When the shingles stay in place, no one can see the condition of the wood underneath. Rotten decking, weakened sections or mould remain hidden under the old roof covering. These problems then get worse silently for years under your new roof.<\/span><\/p><p><span style=\"font-weight: 400;\">The second risk involves trapped moisture. Old shingles hold moisture, especially if they\u2019re already damaged. When they\u2019re covered with metal, this moisture can no longer evaporate. It therefore attacks the deck from the inside and speeds up its deterioration. As a result, your new roof sits on a base that\u2019s deteriorating.<\/span><\/p><p><span style=\"font-weight: 400;\">The third risk affects ventilation. Adding an extra layer changes the airflow in the attic. Inadequate<\/span><a href=\"https:\/\/metalroofcanada.ca\/en\/energy-efficient-roof\/\"> <span style=\"font-weight: 400;\">ventilation<\/span><\/a><span style=\"font-weight: 400;\"> creates condensation that damages the insulation and roof frame. In fact, it\u2019s one of the most common reasons for warranty denials.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-69699b6 elementor-widget__width-initial elementor-widget elementor-widget-image\" data-id=\"69699b6\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"960\" height=\"640\" src=\"https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-1024x683.png\" class=\"attachment-large size-large wp-image-4707\" alt=\"Maison en pierre coiff\u00e9e d&#039;un toit noir \u00e0 joints debout en automne, r\u00e9sultat d&#039;un toit en m\u00e9tal sur bardeau existant.\" srcset=\"https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-1024x683.png 1024w, https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-300x200.png 300w, https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-768x512.png 768w, https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-1536x1024.png 1536w, https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-2048x1365.png 2048w, https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-18x12.png 18w, https:\/\/metalroofcanada.ca\/wp-content\/uploads\/2026\/10\/Toit-en-metal-sur-bardeau-existant-in-text-600x400.png 600w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-24ca024 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"24ca024\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-533c660 elementor-widget elementor-widget-heading\" data-id=\"533c660\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">What the Construction Code says\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-0af3071 elementor-widget elementor-widget-text-editor\" data-id=\"0af3071\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">In Quebec, the Construction Code limits the number of layers of roof covering. In general, a maximum of two layers is allowed. If your roof already has two layers of shingles, it\u2019s therefore illegal to add a third.<\/span><\/p><p><span style=\"font-weight: 400;\">In addition, some municipalities require complete removal when changing the type of material. Switching from shingles to metal may require a<\/span><a href=\"https:\/\/metalroofcanada.ca\/en\/roof-replacement-permit\/\"> <span style=\"font-weight: 400;\">permit<\/span><\/a><span style=\"font-weight: 400;\"> that requires removal. Check with your urban planning department before making your decision.<\/span><\/p><p><span style=\"font-weight: 400;\">The<\/span><a href=\"https:\/\/www.rbq.gouv.qc.ca\/en\/you-are\/citizen\/renovation-work\/construction-and-renovation-standards\/\"> <span style=\"font-weight: 400;\">R\u00e9gie du b\u00e2timent du Qu\u00e9bec<\/span><\/a><span style=\"font-weight: 400;\"> also recommends inspecting the deck during any roof replacement. This inspection is only possible if the old roof covering is removed. Going over the top eliminates this essential verification step.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-5560b14 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"5560b14\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-628402f elementor-widget elementor-widget-heading\" data-id=\"628402f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">What Metal Roof Canada recommends\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-22edd45 elementor-widget elementor-widget-text-editor\" data-id=\"22edd45\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><a href=\"https:\/\/metalroofcanada.ca\/en\/about-2\/\"><span style=\"font-weight: 400;\">Metal Roof Canada<\/span><\/a><span style=\"font-weight: 400;\"> recommends complete removal of the existing shingles before installing a metal roof. This position is based on years of experience and a commitment to long-term quality.<\/span><\/p><p><span style=\"font-weight: 400;\">By removing the shingles, the roofer can access the deck and inspect every section of wood. Rotten or weakened areas are replaced immediately. The installation therefore starts on a sound, verified base.<\/span><\/p><p><span style=\"font-weight: 400;\">It\u2019s also the ideal opportunity to improve the attic insulation and ventilation. These two elements directly influence the lifespan of your new roof. A metal roof installed on a new deck, with adequate insulation and ventilation that meets standards, will perform at its best for 50 years or more.<\/span><\/p><p><span style=\"font-weight: 400;\">In addition, removal protects your manufacturer\u2019s warranty. The 50-year non-prorated<\/span><a href=\"https:\/\/metalroofcanada.ca\/en\/metal-roof-warranty\/\"> <span style=\"font-weight: 400;\">warranty<\/span><\/a><span style=\"font-weight: 400;\"> on<\/span><a href=\"https:\/\/www.ssab.com\/en\/brands-and-products\/greencoat\"> <span style=\"font-weight: 400;\">SSAB GreenCoat steel<\/span><\/a><span style=\"font-weight: 400;\"> requires an installation that complies with the manufacturer\u2019s specifications. Installing over existing shingles may compromise this coverage. It\u2019s a risk that saving a few thousand dollars doesn\u2019t justify.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-460b0e7 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"460b0e7\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-21c2904 elementor-widget elementor-widget-heading\" data-id=\"21c2904\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">The exception: when it\u2019s acceptable\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-361aa7c elementor-widget elementor-widget-text-editor\" data-id=\"361aa7c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">In some specific cases, installing over shingles can be considered. The shingles must then be in good overall condition, with only one layer in place. The deck underneath must also be recent and sound.<\/span><\/p><p><span style=\"font-weight: 400;\">In concrete terms, this approach may be suitable if your shingles are less than 10 years old, show no bumps, cracks or rot, and if your attic is well ventilated. An experienced roofer can assess these conditions and give you an honest opinion.<\/span><\/p><p><span style=\"font-weight: 400;\">However, even in these favourable situations, the result will always be inferior to an installation on a bare deck. You\u2019re accepting a compromise in exchange for a saving. So make sure you fully understand what you\u2019re giving up before choosing this option.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-9a1fc84 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"9a1fc84\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-d1de3dd elementor-widget elementor-widget-heading\" data-id=\"d1de3dd\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">The real cost of each option\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d4752e6 elementor-widget elementor-widget-text-editor\" data-id=\"d4752e6\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">The price difference between the two approaches is smaller than you might think. Here\u2019s a comparison for a 1,200-square-foot home.<\/span><\/p><ul><li style=\"font-weight: 400;\" aria-level=\"1\"><b>With shingle removal:<\/b><span style=\"font-weight: 400;\"> add between $1,200 and $3,600 to the total cost for removing, transporting and disposing of the old shingles.<\/span><\/li><li style=\"font-weight: 400;\" aria-level=\"1\"><b>Without removal:<\/b><span style=\"font-weight: 400;\"> you save this amount, but you add the cost of the support battens, about $800 to $1,500.<\/span><\/li><\/ul><p>\u00a0<\/p><p><span style=\"font-weight: 400;\">The net saving is therefore between $400 and $2,100. In return, you give up the deck inspection, you risk moisture problems and you may compromise your warranty. On a total investment of $25,000 or more, this saving represents less than 10%. That\u2019s a small percentage for a significant risk.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-a9f0c42 e-con-full e-flex wpr-particle-no wpr-jarallax-no wpr-parallax-no wpr-sticky-section-no wpr-column-slider-no wpr-equal-height-no e-con e-child\" data-id=\"a9f0c42\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t<div class=\"elementor-element elementor-element-2a7ff7a elementor-widget elementor-widget-heading\" data-id=\"2a7ff7a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Conclusion<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e4b04cf elementor-widget elementor-widget-text-editor\" data-id=\"e4b04cf\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"font-weight: 400;\">Installing a metal roof over existing shingles is technically possible, but rarely the best decision. The saving is modest and the risks are real. An uninspected deck, trapped moisture and a compromised warranty aren\u2019t worth saving a few hundred dollars.<\/span><\/p><p><span style=\"font-weight: 400;\">Investing in complete removal gives you a roof installed by the book, on a verified base and with a fully valid warranty. It\u2019s the difference between a roof that lasts 30 years and one that lasts 50.<\/span><\/p><p><span style=\"font-weight: 400;\">Torn between the two options?<\/span><a href=\"https:\/\/metalroofcanada.ca\/en\/contact-us-2\/\"> <span style=\"font-weight: 400;\">Contact Metal Roof Canada<\/span><\/a><span style=\"font-weight: 400;\"> for an honest assessment of your situation and a quote tailored to your project.<\/span><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>","protected":false},"excerpt":{"rendered":"<p>Installing a metal roof over existing shingles is a question many homeowners ask their roofer. The idea is appealing: avoid removing the old shingles, save on labour and shorten the timeline. Indeed, it\u2019s technically possible in some cases. However, it isn\u2019t always the best option. In this article, we explain when this approach works, when it causes problems and why most specialized roofers recommend complete removal instead. You\u2019ll thus have all the information you need to make the right decision. How it works in practice The principle is simple. Rather than removing the worn shingles, the contractor installs a system of battens or furring strips over them. These battens create a flat, even surface to which the metal panels are then fastened. The old shingles therefore remain in place under the new roof covering. This method gained renewed popularity after the 1998 ice storm in Quebec. Insurance companies at the time paid for metal roofs to be installed directly over damaged shingles. It was then the fastest solution to protect thousands of homes. Today, some contractors still offer this option. Indeed, it can save a few thousand dollars on the cost of removing and disposing of the old shingles. However, this short-term saving hides risks that every homeowner should know about before saying yes. The advantages of leaving the shingles in place Installing a metal roof over existing shingles has some real advantages. That\u2019s why this option comes up so often in discussions. Savings on removal: removing the old shingles costs between $1 and $3 per square foot in labour and disposal fees. On a 1,200-square-foot home, that therefore represents between $1,200 and $3,600 in savings. Less waste: the old shingles don\u2019t end up in the landfill. This is a concrete environmental benefit, especially since shingles are practically never recycled in Quebec. Faster job: without removal, the work moves faster. Your home is thus exposed to the elements for less time during the transition. Extra layer: the old shingles add a protective membrane between the deck and the metal panels. \u00a0 These advantages are real, but they only tell part of the story. The associated risks deserve just as much attention. The risks to understand Most specialized metal roofers advise against installing over existing shingles. Their reasons are concrete and based on years of experience in Quebec. The first risk is the inability to inspect the deck. When the shingles stay in place, no one can see the condition of the wood underneath. Rotten decking, weakened sections or mould remain hidden under the old roof covering. These problems then get worse silently for years under your new roof. The second risk involves trapped moisture. Old shingles hold moisture, especially if they\u2019re already damaged. When they\u2019re covered with metal, this moisture can no longer evaporate. It therefore attacks the deck from the inside and speeds up its deterioration. As a result, your new roof sits on a base that\u2019s deteriorating. The third risk affects ventilation. Adding an extra layer changes the airflow in the attic. Inadequate ventilation creates condensation that damages the insulation and roof frame. In fact, it\u2019s one of the most common reasons for warranty denials. What the Construction Code says In Quebec, the Construction Code limits the number of layers of roof covering. In general, a maximum of two layers is allowed. If your roof already has two layers of shingles, it\u2019s therefore illegal to add a third. In addition, some municipalities require complete removal when changing the type of material. Switching from shingles to metal may require a permit that requires removal. Check with your urban planning department before making your decision. The R\u00e9gie du b\u00e2timent du Qu\u00e9bec also recommends inspecting the deck during any roof replacement. This inspection is only possible if the old roof covering is removed. Going over the top eliminates this essential verification step. What Metal Roof Canada recommends Metal Roof Canada recommends complete removal of the existing shingles before installing a metal roof. This position is based on years of experience and a commitment to long-term quality. By removing the shingles, the roofer can access the deck and inspect every section of wood. Rotten or weakened areas are replaced immediately. The installation therefore starts on a sound, verified base. It\u2019s also the ideal opportunity to improve the attic insulation and ventilation. These two elements directly influence the lifespan of your new roof. A metal roof installed on a new deck, with adequate insulation and ventilation that meets standards, will perform at its best for 50 years or more. In addition, removal protects your manufacturer\u2019s warranty. The 50-year non-prorated warranty on SSAB GreenCoat steel requires an installation that complies with the manufacturer\u2019s specifications. Installing over existing shingles may compromise this coverage. It\u2019s a risk that saving a few thousand dollars doesn\u2019t justify. The exception: when it\u2019s acceptable In some specific cases, installing over shingles can be considered. The shingles must then be in good overall condition, with only one layer in place. The deck underneath must also be recent and sound. In concrete terms, this approach may be suitable if your shingles are less than 10 years old, show no bumps, cracks or rot, and if your attic is well ventilated. An experienced roofer can assess these conditions and give you an honest opinion. However, even in these favourable situations, the result will always be inferior to an installation on a bare deck. You\u2019re accepting a compromise in exchange for a saving. So make sure you fully understand what you\u2019re giving up before choosing this option. The real cost of each option The price difference between the two approaches is smaller than you might think. Here\u2019s a comparison for a 1,200-square-foot home. With shingle removal: add between $1,200 and $3,600 to the total cost for removing, transporting and disposing of the old shingles. Without removal: you save this amount, but you add the cost of the support battens, about $800 to $1,500. \u00a0 The net saving is therefore between $400 and $2,100.<\/p>","protected":false},"author":1,"featured_media":4706,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[87],"tags":[],"class_list":["post-4956","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-non-classe-fr-en"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Metal roof over shingles: a good idea?<\/title>\n<meta name=\"description\" content=\"Installing a metal roof over existing shingles is possible, but not always recommended. 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