Standing seam metal roofing over asphalt shingles

[Swamp_Yankee]

Anyone ever do this?  We have an older farmhouse that had a major renovation done 20 years ago in which some new roof was installed over the new addition and the old roof was torn off and replaced over the existing house so only one layer of shingles currently.  The shingles are standard 30 year three tab that are 2/3 of the way through their life, I'm just thinking ahead and if we have the money to do it in the next couple of years I'd like to cover them with metal roofing rather than wait for a leak to develop.  We don't have any leaks currently, but we do battle with grey squirrels and flying squirrels which have chewed through flashing and fascia boards and found their way into the attic and soffits.  This is one of my motivations for metal roofing aside from the look.  

We are out in the woods with no other houses around so we're not worried about "fitting" with the neighborhood.  Our barn has grey colored standing seam roofing that is old and weathered and I'd like the house to have the same look.  The barn roofing was simply bought in 12' x 3' sections and installed over purlins spaced 2' OC.  The runs on the roof are 12' and 16', so with 12' panels on the 16' runs I would just plan to lap the section closest to the peak over the lower section according to manufacturer specs, seal the joints with silicone, and stagger the seams (ie: 4' panel at peak, 12' panel to edge of roof, 12' panel at peak, 4' panel to edge of roof, etc...).  It seems to me that this would probably the last roof I'd ever put on this house (I'm 37 years old and plan to stay here for rest of my life)-am I missing anything here?

[MGHunter66]

You can’t go with standing seam over asphalt shingles, you have to remove the shingles, put the appropriate underlayment( not tar paper) then install the standing seam. Standing seam is great, lasts a long time but has to be done properly 

[Swamp_Yankee]

4 minutes ago, maximus66 said:

You can’t go with standing seam over asphalt shingles, you have to remove the shingles, put the appropriate underlayment( not tar paper) then install the standing seam. Standing seam is great, lasts a long time but has to be done properly 

Not challenging you, but what is the reasoning?  

[MGHunter66]

The asphalt under the standing seam heats up causing over expansion and buckling, also voids manufacturers warrenty

[Swamp_Yankee]

Just now, maximus66 said:

The asphalt under the standing seam heats up causing over expansion and buckling, also voids manufacturers warrenty

I'm not really sure how the expansion and buckling would happen.  Asphalt shingles get hot because they are dark in color and absorb radiant energy from the sun.  If they are not exposed to the sun (and furthermore covered with a material that reflects, rather than absorbs radiant energy) I don't know how they could possibly get so hot?  Also, these manufacturers don't have any issues with installation over asphalt:

http://www.unioncorrugating.com/installs-over-existing.html 

https://www.metalroofingsource.com/install-metal-roof-over-shingles/

For the record, I wasn't really asking if it can be done (it seems pretty clear that it can be), but rather, has anyone else done it, what are the potential pitfalls, tips, etc...  

[jerseyhunter]

I would definitely go over the shingles for 2 reasons. Added insulation and sound proofing.  Being a roofer for over 50 yrs dealing with,  Slate, Hot Tar, Shingles and Rubber (both torch down and chemically sealed  ) I believe I'm qualified in replying.

[NJREALTOR]

The metal roofing is way more expensive than asphalt shingles. and you probably don't want to hear the noise from it during a storm. Standing seam is usually installed over framing (hat track etc.)  

The surface has to be straight, or you will see the oil canning.  I probably qualify to respond as I've been a carpenter for 35 years and did way too much roofing.  Over 22 years as a Union Carpenter Local 254 (now)

[MGHunter66]

5 hours ago, Swamp_Yankee said:

I'm not really sure how the expansion and buckling would happen.  Asphalt shingles get hot because they are dark in color and absorb radiant energy from the sun.  If they are not exposed to the sun (and furthermore covered with a material that reflects, rather than absorbs radiant energy) I don't know how they could possibly get so hot?  Also, these manufacturers don't have any issues with installation over asphalt:

http://www.unioncorrugating.com/installs-over-existing.html 

https://www.metalroofingsource.com/install-metal-roof-over-shingles/

For the record, I wasn't really asking if it can be done (it seems pretty clear that it can be), but rather, has anyone else done it, what are the potential pitfalls, tips, etc...  

Ok first the links you’ve provided I believe are for steel roof panels, not per se standing seam. Standing seam is different than steel whereas the fasteners are hidden. it requires a flat, hard surface for the clips to stay inline so the panels can move with expansion. Other metal roofing systems that don’t use clips and utilize exposed fasteners can go over shingles but have limitations as a less than superior product. Shingles are hardly a flat surface and even though below the metal will in fact heat up moving the clips causing buckles by limiting movement on a real standing seam system.And yes any good standing seam manufacturers warrenty will be voided unless you use the required underlayment applied directly to the roof deck. I operated my own construction company for 30 years and now am the manager of building and construction for a huge entity besides being a registered code official of the state of NJ so i believe i kinda know what i am doing. Do whatever you want, the right way or wrong way is up to you

[Swamp_Yankee]

53 minutes ago, maximus66 said:

Ok first the links you’ve provided I believe are for steel roof panels, not per se standing seam. Standing seam is different than steel whereas the fasteners are hidden. it requires a flat, hard surface for the clips to stay inline so the panels can move with expansion. Other metal roofing systems that don’t use clips and utilize exposed fasteners can go over shingles but have limitations as a less than superior product. Shingles are hardly a flat surface and even though below the metal will in fact heat up moving the clips causing buckles by limiting movement on a real standing seam system.And yes any good standing seam manufacturers warrenty will be voided unless you use the required underlayment applied directly to the roof deck. I operated my own construction company for 30 years and now am the manager of building and construction for a huge entity besides being a registered code official of the state of NJ so i believe i kinda know what i am doing. Do whatever you want, the right way or wrong way is up to you

I did figure out that I was using the wrong terminology-what I posted was "ribbed" roofing I guess.  So standing seam can't installed over asphalt shingles whereas ribbed roofing apparently can. 

[MGHunter66]

4 minutes ago, Swamp_Yankee said:

I did figure out that I was using the wrong terminology-what I posted was "ribbed" roofing I guess.  So standing seam can't installed over asphalt shingles whereas ribbed roofing apparently can. 

Correct, if you do go with metal roofing over asphalt the biggest drawback i could point out is condensation which cause premature deterioration. Good luck with your endeavor 

[hunterbob1]

37 year know it all,asks for help,you offer experience best you can do.

[tcook8296]

I just had a brand new metal roof installed. The underlayment was like a thick rubber layer then they put the panels over top. I have seams on each panel however you cant see any of the fasteners. If it were my house with existing shingles, I would tear the shingles off and have the proper underlayment installed. I dont see how you could get the metal roof to install flat over top of shingles. 

Edited January 29, 2019 by tcook8296

[Bowhunter2004]

My farm house in illinois has a metal roof installed over asphalt shingle on the main part of the house... its a little lumpy, but looks ok for what it is.  If it was my primary residence here in NJ it would be totally unacceptable, but plenty good enough for out there. 

[Swamp_Yankee]

7 hours ago, Bowhunter2004 said:

My farm house in illinois has a metal roof installed over asphalt shingle on the main part of the house... its a little lumpy, but looks ok for what it is.  If it was my primary residence here in NJ it would be totally unacceptable, but plenty good enough for out there. 

It looks damn good to me.  If the main worry is "lumpiness" that's not really a concern for me.  It's an old house and I'd rather it look like an old tin roof that's been there as long as the house has (130 years or so)-not a brand spanking new steel roof.  What brand of panels did you use?  

12 hours ago, hunterbob1 said:

37 year know it all,asks for help,you offer experience best you can do.

Nope-I learned a lot more by reading through this thread ie: the difference between standing seam and ribbed roofing