Should Shingles be Removed Before a Metal Roof is Installed? – Metal Roofing 101 with Todd Miller
Should My Old Shingles Be Removed Before A Metal Roof Is Installed?
Metal roofs are much lower weight than most other roofing materials. Aluminum roofing weighs around 50 pounds per 100 square feet and most steel roofs are 80 – 100 pounds. Traditional shingles for that same size area are 275 – 425 pounds in comparison. This encourages the installation of metal roofs over existing shingles. Additionally, most building codes allow for two layers of roofing to be on a home. Unlike asphalt shingles, installing a metal roof as the second layer should not impact the warranty on the second layer. Doing so often voids the warranty on the second layer of asphalt shingles. Now, if a roof has current issues such as leaks or deteriorated decking including dips and buckles, those must and should be addressed before the new roof is installed, and that may require removing the old shingles. Regardless of whether the old shingles are removed, a layer of underlayment should be installed prior to any metal roof installation. Always make sure, too, that your roof is installed in accordance with manufacturer recommendations. Leaving the old shingles in place has several positive benefits. It increases the building’s thermal mass for energy efficiency. It avoids having to dump old roofing materials in landfills. It reduces the risk of interior or landscaping damage during the re-roofing process. And it allows the homeowners to spend their money on an upgraded roof rather than on removing and disposing of their old roof.
I put shingles on my metal roof, because I don’t follow the crowd
Lol
Your a rebel for sure
Wow, smart move, LOL!
Thanks for the informative and to the point information, it was very helpful.
Professional straight to the point advice. thank you!
One more reason: Quieter during rain or hail.
True. A friend of mine installed metal on top of shingles, and it is just insanely quiet in his house when it rains.
Cotronixco so did you have medal roof put on your home over shingles
Thanks for the question. Rarely do I hear of noise complaints but, yes, leaving the old shingles in place will help with sound transfer. Sorry I did not see your comment sooner!
@1:20 such solid points, well done, thanks
Can a metal roof be added if you have two layers of shingles? Thanks for sharing.
Great question. No ☹️
The low weight of metal roofing does encourage its application over existing roofing, even multiple layers. One thing to consider is the weight that previous layers of roofing have lost due to granule loss and oil evaporation. With a very low weight metal roof, you may not be adding more weight than the last layer of roofing has lost. Additionally, more heavily corrugated or press-formed metal roof products are quite forgiving when installed over uneven roof surfaces. However, building codes in many areas dictate no more than two layers of roofing on a structure. Even if you’re in an area where no such code requirement exists, I still caution about installing over multiple layers of roofing. My concern is that doing so could become an issue or concern at a future date, raised by home inspectors and mortgage companies when you go to sell the home.
..Neil Armstrong’s younger brother.
Is there a specific underlayment which is advised when installing metal over existing shingles? I’m guessing good old-fashioned tar paper….thoughts?
Sorry for the delayed response, David. I would suggest always adhering to the specifications set forth by your roofing manufacturer as well as local building code, but much of the metal roofing industry is now using synthetic products like RoofAquaGuard UDLX.
Hi, Thanks for the video! We have a couple questions:
One roofer offers acrylic coated galvalume metal panels that are 55% TSR. Another offers galvalume panels (no mention of acrylic coating) that are 25% TSR.
Can I assume that the 25% panels are not acrylic coated? Is it important for the galvalume panels to be acrylic coated?
Great question! The acrylic coated product is actually a clear coating so what you see appears to be mill finish metal. The acrylic coating is actually applied to facilitate transportation, forming, and installation of the product. It washes away within 5 – 7 years, leaving you with uncoated Galvalume metal. Your TSR will diminish then as the metal starts to dull down. The other product is a painted product which is superior in terms of durability as the coatings last much longer. There are two basic coating formulations used today – polyester and PVDF. The latter is known for superior fade and chalk resistance over the long term.
remove old shingles to inspect roof decking
what a damn stupid advice.
@James Simmons I really hope you’re not a contractor.
There is no other way to do it. The homeowner is screwing himself if they put a new roof over the old one.
Great idea. Why not remove the house to inspect the ground below? If I were going to do that I’d have done it and not bothered asking about aluminum panels over existing asphast shingles. Sheesh !!!
@Martin Rits Not really we put a metal roof over asphalt shingles, over 15 Years ago without a single leak or other problem. There some who recommend putting roofing paper between the shingles and the metal roof.
how do you know what you are nailing to with the shingles on rot underneath roof blows off someday take shingles off completely
Any areas of existing roof leaks, rot, or “spongy” decking should be addressed. These can be observed from the attic space in many cases as well as from walking on the roof. One option is to do pull out resistance tests on fasteners. In suspect areas of the roof, drive in some fasteners like those that will be used for the roof system, drive them through a metal strap that can then be looped and connected to a farm scale. I would look for pull out resistance of no less than 50 pounds, and preferably 80+ pounds.
Can you please answer this question? In the Pacific northwest we have problems with moss growing on roofs. My 45 year old asphalt shingle roof is thus affected. I can knock most of it off but it will grow back. The question is this: Is it OK to clean the existing roof as well as one can and then install the new aluminum roofing. The prospect of moss remaining between the two layers of roofing is one that I can’t answer. Will moss continue to grow? It is a fact that moss grows better in the shade. There will be plenty of shade under the aluminum. Please, in your answer don’t concern yourself with questions of insurance or warantee. My home has been paid for for quite a while and I do my own home maintenance because I consider such work to be fun.
note: I use a pressure washer to remove moss but it always grows back. Those products that claim to kill moss are a waste of money. They do nothing except to empty your wallet.
Remove the shingles as they hold water and organic materials that Moss thrives on. Then put metal on with a good underlayment first. Not tar paper.
@James Simmons Copper is installed at the peak of the roof, trace elements of copper dissolve in the rainwater and poison the algae or moss. This is a common practice in the southeastern U.S. I’m not sure if it works in the N.W. U.S.
Pressure washing is contraindicated for cleaning roofs. This is a case where chemicals are your friend. You can find different formulations but one safe and effective one is a bleach/water/soap mix that will kill any moss or algae on your roof and inhibit its regrowth. Then you can lay down your metal. I hope this helps.
Please explain. @Jeff Hallel
Have you tried copper?
The shingles distort the metal make it look horrible. Fighting with a contractor right now because it’s buckled so badly. He’s blaming it on the shingles.
Every situation is unique. However, generally speaking, standing seam is not very forgiving for installations over old shingles. Is yours a standing seam roof?
My current roof has 2 layers of shingles on my home. I am considering a metal roof. Does the shingles have to be removed prior to the metal roof being applied? There are not leakage problems with the current roof
Yes
Many metal roofs, especially those with great formation to them, can be installed over old shingles with no visible effects. A layer of new underlayment should be placed over the old shingles first. The low weight of metal roofing is also very helpful to this end. That said, most building codes do not allow more than two layers of roofing. Even if you are in an area where building codes are not enforced, I caution on allowing a third layer as it could be a red flag for a future home inspector or mortgage company if you go to sell your home.
Sharon Wighent yes, they will have to be removed
NEVER put a roof over another roof. None of the reasons you give are valid. 30 plus years experience.
@Rick you need to read all my comments. I said I won’t take a job where the homeowner wanted to screw himself. Guess who gets the blame when he has a roof problem. I never have and never will put a new roof over an old one.
@Michayal Valder just say u dont make enough money if u dont do the tear off.. double charging for the dumpster when all u do is order it..charging double the wage for a guy u picked up outside the temp service
@Rick I won’t even take a job where the homeowner wanted a new roof over an old one . Don’t need the problems.
spoken like a man that gets paid more if he has to put a lot of work into the removal of an old roof..
My question is, if shingles aren’t removed and metal put on top, wouldn’t that put extra weight on the frame that it wasn’t built for extra weight ? Does anyone else ask this ? I’m in a double wide mobile home and we had 3/4″ hardwood floors installed but we had to put extra support to the floor beams/joists to handle the extra weight from 3/4″ subflooring and 3/4″ hardwood because the home wasn’t built for extra. Wouldn’t the same be for the roof also ? Thanks
@Isaiah Industries Thank you
Thanks for your question. Building codes in most areas allow for two layers of roofing, so homes generally are designed and built for that weight load. Each layer of asphalt shingles can weigh up to 350 pounds per 100 square feet or even more in some cases. Metal roofing is actually much lower weight – aluminum roofs weight from 45 – 70 pounds per 100 square feet and steel is typically from 80 – 125. I would suggest checking with the manufacturer of your home for further input as well as the structural requirements and limits of your home.
Can i add a new tin roof on an existing tin roof? My tin roof is above a loft space that i wish to open up to the rooms below. there is a deck made from boards which is nailed to the rafters and the old tin panels nailed to that. I wish to add EPS and a air tight reflective layer with an airspace between that and the new tin which will be screwed down. I will also add some eps between the rafters and another reflective air tight layer of silver sheet/foil before one final airspace and then drywall or wooden boards to finish the inside.
Should i be worried about damp/condensation and how important is the underlayment? How does it function? top floor of the house is 40M2 and has a living space below, some of the ceiling will remain closed but some parts will be opened up to mezzanines, open space and cupboards above. We live in a fairly dry area that can get to -15C and can be fairly warm in the summer.
Condensation occurs when warm moist air hits a cool surface. Normally, this is when warm moist air originating inside the structure reaches a cold area in the roof system, such as the back of a roof deck. When this happens and dewpoint is achieved, condensation occurs. Ways to prevent this from happening include a vapor barrier behind the home’s ceilings to prevent moisture migration, ventilation to vent out warm moist air, and/or insulation to prevent the thermal bridging of outside cold temperatures into the structure. Usually it takes at least two of these three things to be successful.
It sounds like you are onto a good plan. Make sure that the manufacturer of your roofing material is okay with what you’re doing.
Underlayment should be directly beneath the roof system. It is required by code and is there to protect the structure during installation, in the event of storm damage to the roof, and even if the roof should bleed some water on occasion. I hope this helps. Feel free to email me at todd@asktoddmiller.com if you have additional questions.
Yes
Thank you.
Wow that background music made me sad. I thought I clicked on a funeral home advertisement