For Professionals | Member Login
Find a Professional
Sign Up Log In Add New Topic

TOPIC: Installation

metal over shingles w/out furring strips?

Return to Installation

Return to Forum

I recently had a contractor come out and install a nice metal roof over asphalt shingles. When we signed the contract furring strips were supposed to be put added. No underlayment was installed and the strips were not either. The guy who installed it said that the owner had no idea what he was talking about and it was irrelevant to have the wood attached. After browsing many forums i can see a few different opinions on the matter and just want to know, is it worth going to court over for a breach of contract or is the installer correct and its better that i do not have them? Thank you in advance from a floor guy!
Guest User

11/21/2013
I would like to know more about exactly what type of panel was installed. However, I would say that the battens probably were not essential though they can enhance energy efficiency. As far as underlayment, I strongly recommend it to prevent abrasion between the back side of the metal and the granulated shingle surface. I also interpret the International Building Code as including underlayment as a requirement. However, the code is not applicable / in place in all areas. Additionally, not everyone interprets the code the same as I do. Todd Miller
Todd Miller
Isaiah Industries, Inc.

11/21/2013
+1 Metal, depending on the panel, can be installed either with or without battens. The lack of underlayment or slip layer is wholly incorrect in my opinion though regardless of application. Eric Novotny
Eric Novotny
An informed customer is the Best Customer!

11/22/2013
I'm building a tiny house and was planing on 2x6 rafters (cavity filling with insoleshin ) 1/2 osb sheathing, weather watch barrier, then furring striping on top horizontally, then (Classic Rib Steel Roof Panel). Was wondering the best spacing? Or if I should go a different route?
Guest User

8/20/2014
Elton, that does not sound unreasonable. The batten spacing specification will be based upon exactly what metal roofing panel you are installing. The manufacturer should be able to tell you what is required. Todd Miller
Todd Miller
Isaiah Industries, Inc.

8/21/2014
I am installing a metal roof on a single wide trailer it has shingles on it I plan to remove and lay metal on the plywood I have been told I must use 2×4 perlins are they necessary also the roof has a vent that runs the length of the trailer I plan to remove it as well and run the metal over it is that acceptable
Guest User

8/21/2014
Andrew, once the old shingles are stripped, the plywood needs to be covered with underlayment even if you apply battens. Some products can be installed on battens. Some cannot be. Some must be. So, basically, part of that decision comes down to the product you choose. However, trailers often have moisture issues. Putting the roof up on battens will help prevent creating a situation where dew point occurs in the plywood decking causing condensation. Putting the roof on purlins will help keep your roof deck a little warmer which, in order to avoid condensation, is a good thing. I would absolutely not remove the ridge vent. We need to make sure that moisture generated inside the home is vented outward so that it does not condense in the attic. Todd Miller
Todd Miller
Isaiah Industries, Inc.

8/22/2014
So Todd- In your opinion (considering the expense) is it worth while to apply 1x4" purlins before installing the panels? The panels are 3 ft. wide ? Steve Saxon
Steve Saxon
Roofer

11/4/2014
Todd- In your opinion is it necessary or even logical (considering the expense) to apply batten boards before installing the panels. Also couldn't this process also be a problem after the install when walking on it?
Steve Saxon
Roofer

11/4/2014
Is it ok to screw 29 gauge metal over the top 3 tab shingles with synthetic felt in between
Guest User

9/13/2016
John, Quite a normal application and done all the time. If you are looking for above decking venting (i.e. additional cooling), so folks will strap the roof for a vent space application. Eric Novotny
Eric Novotny
An informed customer is the Best Customer!

9/14/2016
I was told by a contractor that if they put a metal rood over existing shingles that there could be a fine is caught to the property owners. In the the state of PA is this true?
Guest User

9/22/2016
Hi Lynn, The International Building Code allows up to two layers of roofing on residential buildings. This includes if the first layer is shingle and the second layer is metal. The low weight of metal helps to support this practice. This code is not enforced in all areas but I am not aware of any local or state codes that are as you have been told. The only way to know for certain would be to contact the building officials with jurisdiction in your area. I will say this ... it's not unusual to see 3 or even more layers of roofing on some buildings. This though could become a problem if the home is sold in the future and the home inspector or new owner's mortgage company wants to take exception to what was done. Todd Miller
Todd Miller
Isaiah Industries, Inc.

9/22/2016
Sounds more like a contractor that is trying to scare someone unless he is providing more data than that. A roof over is a pretty normal and well accepted procedural approach. Where is becomes and issue is with multiple layers as Todd mentioned. Eric Novotny
Eric Novotny
An informed customer is the Best Customer!

9/22/2016
I am looking into getting a metal roof installed over shingles onto my home. 29 Guage is what I've been quoted prices on. One contractor says you are making a mistake if you don't first have the roof stipped with 1x4 and another says it's a waist of money to strip?! My roof is quite steep. I'm confused! Help!
Guest User

5/1/2017
Thanks, Misty. I believe that I just emailed you direct to address your questions. Please let me know if you do not receive my email. Todd Miller
Todd Miller
Isaiah Industries, Inc.

5/1/2017
I've got an older double-wide (1987) with no attic or ridge vent. I've had the roof patched after a couple of bad storms. My question is, before I prep for the metal roof, how flat does the roof need to be before I lay down the felt and furring strips. There are several spots on the back side missing shingles. Is it necessary to patch these spots as well, or will the felt and strips be level enough to screw the metal straight to it. Also, is there any way to cut a ridge vent where the halves meet. There is no attic, so i haven't seen a solution to this problem. Would be nice, since in South Carolina it gets hot, and my main living area has vaulted ceilings. Very informative site. Nice Job!
Guest User

5/2/2017
The lathe boards should make up for small amounts of unevenness from missing shingles. They will not make up for larger dips and swales in the roof. Here is a link to a short video regarding battens that may be informative for you: https://www.youtube.com/watch?v=pEWcwNg29Ag You probably can cut back the decking at the ridge form the outside though your ridge boards will require you to cut back pretty far and that will likely then require a custom over-sized ridge vent. Keep in mind, though, if you have not soffit (eave) vents and a clear pathway for air to come in and travel to the ridge, a ridge vent will not function and, in fact, could end up drawing water in at the ridge or pulling moisture in through the home's walls. Todd Miller
Todd Miller
Isaiah Industries, Inc.

5/2/2017
Hello Todd, We had a leak and we had put some tar to stop it but wasn't working so We had a roofer install a metal snap-tite roof on top of our old shingles.Our home is a low slope manufactured 2-12..or 3-12 at best..he didn't put anything on top of the old roof just metal no felt or wood strips..I know this because I watched part of the day. Will our roof be okay?
Guest User

6/7/2017
Crystal, first of all, what's been done is not unheard of. However, I do have some questions. Where are you located? Is there any attic ventilation at all in the home? Have you ever had any issues with condensation in the home or ice dams on the roof? Todd Miller
Todd Miller
Isaiah Industries, Inc.

6/8/2017

If you would like to reply to this thread, please log in. If you do not have an Ask the Experts forum user account, create one here.