Monday, April 8, 2024
HomeFactsIs It Ok To Roof Over Existing Shingles

Is It Ok To Roof Over Existing Shingles

How Do You Tie In Shingles To An Existing Shingles

How to Install Roof Shingles | Ask This Old House

Tying into an existing roof shingle that needs the expertise of an ardent roof contractor who will hack the job and deliver a flawless result.

Things to consider before you opt for a reroof:

  • Make sure to check if the building code in the area you reside in allows the process of laying a new roof on top of an existing one, and if it does, how many layers are acceptable.
  • The roof is an integral part of the building that keeps the home in general safe and warm all year round for this reason, ensure to mind the roof deck, the eaves edge, and the valleys when you begin the project.
  • Because you will not be changing the roofing material, ensure that the roofing accessories, for example, the flashings and valley liners march up with the quality with roofing material so that the entire roof will age in style.
  • With an extra layer of shingles in place, more heat will be trapped in the attic, ensuring that the air vents in the area are sufficient because the roof will be preserved with a sound venting system and will rot with too much moisture.
  • Requirements needed before embarking on a reroof:

    • New shingles

    Difference Between Reroofing And Roof Replacement

    Roofing over an existing roof is also called reroofing or an overlay. It is the process where roofers install a new roof over your existing one, i.e. add a new layer of shingles, which means that the old roof will not be removed/teared off.

    Roof replacement is the process of installing a completely new roof that includes the tear-off of the old one. Roofers will tear everything off, down to the deck of the roof, and basically start from scratch with the new roof, from putting an underlay e.g. Armourbase Pro Plus and then installing the new shingles.

    Concerns With Layering Shingles

    Of course, this cost benefit comes with some concerns and risks. An important thing to consider is the extra weight new shingles will add to the roof. Asphalt shingles come in a few different grades and thicknesses. The basic 3-tab shingles are rather flat and light, but the 3D architectural shingles are much thicker and heavier. Layer enough of those, add the snow weight and your roof may collapse unable to support the weight.

    Another risk to consider is the condition of your current roof. Unless you remove the existing shingles, you are generally not able to see any hidden damage underneath. Your roof deck could be rotten or about to fail, which means you will waste time and money on new shingles that will soon have to come off. This layering approach also wont let you to install any protective membranes over the roof deck, which your roof may or may not currently have.

    Don’t Miss: Why Do Business Buildings Have Flat Roofs

    Manufacturer Specifications And Warranty

    Even with the best warranties, it may be hard to track someone down after 40 or 50 years so they can assess your roof and write you a check for any damage. Depreciation may also significantly reduce the amount youd receive. This is why its good advice to purchase the best product you can afford, follow the specifications of the manufacturer, and have it installed properly. Then, you can pitch the warranty after about five years.

    New Shingles Not Sealing Down

    My roof should have a drip edge or overhanging shingles ...

    Standard asphalt shingles feature an adhesive strip that softens during warm weather, especially when the suns rays hit the roof directly. When the shingles heat up, they become flexible and the adhesive bonds the shingles in place. Before new shingles seal down, they can look a little lumpy and uneven, but once the roof gets hot enough, they should soften, flatten and form a permanent seal. Sometimes this problem is more apparent on north-facing roof slopes that dont heat up sufficiently for the shingles to seal until summer. Usually this isnt a major issue, but if you live in an area that is very windy, your roofer can apply temporary adhesive to prevent the wind from catching the edge of the unsealed shingles and blowing them off.

    You May Like: Where To Get Roof Trusses

    Can You Put A Metal Roof Over Shingles

    Yes, its possible to put metal roofing over shingles. Before you get started on your project, though, you will need to check with your local building department to see if theyll allow you to. Some areas will only allow re-roofing over one layer of shingles while others will allow over two layers. There are also some disadvantages to installing metal roofing over shingles that youll want to know about before starting. Contact your local roofing company to learn more and see what they can do for you.

    Should Old Shingles Be Removed

    The importance of having a proper roof over your head is to provide shelter, but an adequate roof goes ahead to also protect the overall building from damage. Roofs get old, and when they do, a replacement should be on the offing.

    Because reroofing is not a foreign idea, many may choose to take that route, but if you are still undecided, here are reasons why tearing off the existing roof before installing a brand new one is good:

  • Proper Installment
  • The advantage of tearing off a damaged roof is that your new roof will benefit from a proper installment.

    When the old roof is out of the way, the new top starts from scratch and has the potential of being laid on a flat surface with no obstructions therefore, it will be firmly attached, and the entire roof will have an even surface.

  • Saves Money
  • The biggest reason behind reroofing is that homeowners have this fancy idea that they aresaving money in labor, shortening the time needed to complete the project, and finding it easy to manage the roof replacement process.

    The truth is that reroofing is a bad idea because the layers of roofing materials stalked on top of each other will need to be dismantled at the end of the day. The homeowner will pay more money to have it torn apart as it will involve more than tearing off one layer after another.

    Overall, reroofing in the name of cost management is just a delay tactic.

  • Obstruction Of Roof Inspection
  • General Outlook
  • Product Warranty
  • You May Like: How Long Should An Asphalt Roof Last

    Is It Ok To Have Two Layers Of Shingles

    Warranty issues: Most shingle warranties do not apply when shingles are layered over existing roofing, according to InterNACHI. Two layers of shingles trap more heat, which in turn damages the shingles and shortens the life span of the roof.

    How long does a reroof last?

    Homeowners with wood shake roofs should expect them to last about 30 years, while fiber cement shingles last about 25 years and asphalt shingle/composition roofs last about 20 years, the NAHB found. Climate and weather conditions, such as snow, hail and hurricanes, can cut the life span of all types of roofs.

    Flashing And Additional Rows Of Shingles

    Asphalt Roof Shingles Installation

    Flashing must be installed correctly around elements, such as vents or chimneys, that penetrate the roof, as well as in valleys where different parts of the roof meet. When doing a layover, the thickness of the layers can make it difficult to use any method other than metal valley flashing. To install, line the valley with underlayment secured with roofing cement. Cut the flashing into 6- to 8-foot lengths to help prevent buckling after installation. Apply roofing cement to the back of the flashing, then nail it into place, keeping all nails a minimum of 6 inches from the flashing’s centerline. The edges of the valley flashing should be under the new shingles. Continue installing the rest of the shingles by butting each new row snugly against the bottom of the existing row of shingles immediately above and nailing into place.

    Read Also: Should You Replace Roof Before Installing Solar Panels

    Can Metal Roofs Be Installed Over Shingles

    In simplest terms: Yes, you can install a metal roof over shingles. However, youll want to check with your local building department before you make any decisions. Building officials in some areas will only allow a re-roof over one layer of shingles, while officials in other places may allow you to place the roof over two layers of shingles. Fortunately, in most areas, it wont be an issue if youre only going over one layer.

    Section 1511.3.1 of the 2018 International Building Code 1st Edition states, The installation of a new roof covering over an existing roof covering shall be permitted where any of the following conditions occur2. Complete and separate roofing systems, such as standing-seam metal roof panel systems, that are designed to transmit the roof loads directly to the buildings structural system and that do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.

    So, its possible to have the installation of metal roofing over shingles, which is great news! But you might be wondering what the advantages and disadvantages are and what to keep in mind during installation. Keep reading to find out.

    Installation Of Metal Roofing Over Shingles

    If you choose to install metal roofing over shingles, there are certain things you must keep in mind. Were going to break them down, so you know what to look out for. But first, here are a few precautions about the underlying material:

    • Address any existing roof leaks and replace rotten rafters or sheeting.
    • Look out for any signs of the previous roof weighing too much. Signs may include buckling tresses or sagging decking.

    Also, make sure you acknowledge:

    Also Check: How To Install Insulation Under Metal Roofing

    What Is The Average Cost Of Metal Roofing

    On average, metal roofing prices range from $3 to $8 per square foot, with the average homeowner spending about $5 per square foot. Aside from zinc and copper roofs, the cost of a metal roof can be the same as the cost of an asphalt roof if you spread the cost over the life of the roof. The types of metal roofing systems vary widely.

    Can I Put A Second Layer Of Shingles On My Roof

    Pictures of Lean To Sheds

    Can I put a second layer of shingles on my roof? You can, but you probably shouldnt! Known as a layover, putting a second layer of shingles on your roof is in most cases inadvisable and a job that Proven Roofing is likely to even turn down. There are many reasons why you shouldnt do spot repairs and should instead replace your roof entirely, but a layover has its own unique set of cons that merit investigation.

    Don’t Miss: How To Become A Licensed Roofer

    The Importance Of Roof Pitch

    Q: Everything being equal , which roof will last longer: one with a steep pitch or one with a shallow pitch? Seems to me a steep hillside erodes more quickly than a low slope, so I’d think that roof shingles would wear out more quickly on a steeply sloped roof.

    George, Oglesby, Ill.

    A:Tom Silva replies: It’s difficult to say. On one hand, a steep roof is less likely to collect leaves and other debris that hold moisture against the shingles and invite the growth of moss and algae. On the other hand, that same roof in an unshaded area facing due south will take the full brunt of the sun, which is hard on any roof.

    Actually, factors other than pitch have a greater effect on shingle durability. The side facing your worst weather typically fares worse than the leeward side. Likewise, a roof system that isn’t vented properly and allows heat to build up beneath the roofing has a shorter life than one that is vented.

    Pros And Cons Of Reroofing Over Existing Shingles

    Does it look like your asphalt shingle roof is approaching the end of its lifespan? Thats never the type of news homeowners want to hear, because it often means a big expense and a messy project. But did you know that stripping the old shingles and installing a brand-new roof is not your only option? Thats true! In some situations, it may be possible to install a new layer of shingles over your existing shingle roof with similar success. Let our tell you everything you need to know about reroofing.

    Recommended Reading: How Do You Measure Pitch On A Roof

    Can You Put Steel Roofing Over Asphalt

    Can you avoid tearing off your old asphalt shingle roof by putting a steel roof over it? Maybe. Most codes now allow no more than two layers of roofing before requiring a complete tear-off. So, if your roof has two layers, it may require a complete tear-off, even though steel is lighter than asphalt. Codes vary, so call your local building department to know how to install metal roofing over shingles properly, code-wise.

    What’s The Best Way To Remove Shingles From A Roof

    Installing Man-made Slate Roofing Shingles

    If you need to build a roof, check with your local building authority first Regulations generally require you to remove the roof if there are two or more layers or if the existing shingles are crooked. Using airplane scissors, cut the bevel around the vents. Use a chisel to remove the flue gauge liner.

    You May Like: How To Remove Wasp Nest Under Roof

    How Long Will It Take To Install My New Roof

    The time it takes to install a new roof also depends on the size of your home. Building small houses of less than 1,200 square meters generally takes only one day. Large houses of 4000 square meters take days. However, complex structures or very steep slopes can drastically increase the length of your deck.

    When Can You Install A Layover

    Layovers as a repair technique are the equivalent of putting a bandaid on a bandaid. It doesnt look right and it just makes things worse. Even the ideal conditions for a layover arent ideal. Your roof would have to be lacking any of the signifies that repair is necessary, which would mean that youd basically have to have a new roof. But a layover is bad for your new roof!

    A second layer of shingles will decrease the integrity of your new roof and lower its lifespan. Thats because shingles arent designed to have a second layer of shingles on top of them! Plus, all that extra moisture and heat being applied to the first layer of shingles will make that first layer age faster.

    Don’t Miss: Is The Tesla Solar Roof Worth It

    Detail : Ventingthe Ridge

    Cool outside air travels under the shingles to the vented ridge, pulling out moisture and heat.

    A steel roof is a lifetime investment, lasting 50 years or more if its a good one. Asphalt roofs typically last 20 to 30 years, depending on the installation and shingle quality. So, the investment might be worth it, but the range of choices makes shopping for a steel roofing system more complicated than you might think.

    If you want to install steel over asphalt, your best choice for installing metal roofing is to use a steel shingle system like the one shown instead of the more common standing seam steel. In a standing seam roof, long, single panels run vertically all the way from the eave to the ridge. In contrast, steel shingles are small panels installed in horizontal rows much like other shingles.

    Better steel shingle systems, like the one shown, install over a framework of 2x2s. This framework has three big advantages. First, because the frame is screwed directly to the rafters and the interlocked shingles are screwed to the frame, the roof can withstand winds of up to 120 mph without damage. Second, the frame creates a flat and straight surface even when the shingles are badly curled or the roof ridge is bowed.

    Cut And Install New Shingles

    My roof should have a drip edge or overhanging shingles ...

    Any installation of the new shingles must follow manufacturer recommendations. For example, there must be an adequate amount of overlap, and the fasteners must be properly positioned. It is important to use experienced roof technicians who know how to cut new shingles to precisely fit around vents and other roof penetrations.

    Don’t Miss: How Much To Get A Roof Redone

    When Is It Not Recommended To Do A Reroofing

    After their roof inspection, a professional roofer will come to you with his report or a recommendation, explaining why your roof is or isnt suitable for reroofing. You can ask for a few roof estimates from different contractors just to be sure that you are doing the right thing. That way you can choose the best roofer for yourself. One of the main and most straightforward reasons a roof isnt suitable for reroofing is curling shingles, as you can only install a new shingles layer if the existing shingle roof is completely flat and level. A second reason can be the presence of existing damage to the wooden structure underneath, such as rot or sagging.

    Heating Cables For Gutters

    Q: Last winter, we had a serious problem with ice clogging our gutters. And every time it melted a bit during the day, the overflow would spill onto the walkway and driveway and refreeze at night into a sheet of ice. How can we stop this from happening?

    A:Tom Silva replies: One way is to run electric heating cables inside the gutters and downspouts. Turn the cable on during snowy, freezing weather so the water drains away and stays off your walk and drive. Be sure to use cables with thermostatic controls so they don’t overheat or run up your electric bill.

    But these cables only treat the symptom of a bigger problem: inadequate roof ventilation. In other words, the heat escaping from the house is getting trapped under the roof and melting the snow, even when the weather is below freezing. That meltwater ends up refreezing in your gutters.

    A roofing contractor can install the ridge and soffit vents that a properly ventilated roof should have. But if you can’t get this work done before winter, try placing a small box fan in the attic to cool the underside of the roof. Face it towards the area of the roof that gets warm, and run it whenever there is any snow on the roof. That’s a lot less expensive than installing and operating heating cables.

    Read Also: What Does A Roofing Contractor Do


    Most Popular