Mike October 22, 2014Is your metal roof properly installed?
Metal roof installations on residential homes are gaining in popularity. More and more homes are 
sporting a new metal roof. The question for me as your inspector and for you as a home buyer is, has the roof been installed correctly? Unfortunately, many are not. Here is an example of improper flashing practice on a new metal roof. I have numerous pictures of improperly installed metal roofs from inspections I have performed. Unfortunately there are a lot of “contractors” out there that will simply drive up and start slapping on steel. Buyer beware!
Most, if not all of the manufactures that I have read strongly recommend that a residential installation be installed onto a solid deck and not over existing shingles. That requires the existing shingles be removed down to the sheeting and a new layer of either 30# paper be installed or, better yet the roof be covered in high temp ice and water shield. We are talking about best practice here. Not just slapping up steel.
Unfortunately, the majority of metal roofs I see are installed right over the original shingles. In my opinion this is very bad because the installers have no way to determine the condition of the roof sheeting which prevents them from discovering ventilation deficiencies. Proper ventilation is key to a healthy roof, attic and home. These “contractors” are installing possibly the last roof the home will ever see over a deteriorated and potentially damaged substrate. Does that sound like a good idea to you? Of course not. This is why I strongly recommend that you do your do diligence and hire a contractor that will do the job right the first time. Someone with specific experience and who follows the manufactures instructions to the letter. It may cost extra up front, but it will pay off in the long run.
Properly installed metal roofs have several advantages over a composite shingle installation. A few are of them are;
- Longevity: A properly installed metal roof may last anywhere from 30 years to well over a hundred years and beyond, depending on the type of metal used. Types of metal range from galvanized steel all the way to titanium and come in a variety of colors and types.
- Durability: A properly installed metal roof should give you a class 4 impact rating and a class A fire rating provided it meets the appropriate UL standards. These ratings may have a positive effect on your insurance premiums so be sure to check it out before you purchase your materials. Properly installed metal roofs also have very good wind ratings upward of 140 mph. Contrary to popular belief, metal roofing is considerably lighter than other roofing materials as well.
- Efficiency: If the appropriate color is used, a metal roof may reduce heat gain, thereby reducing utility bills up to 15% in the summer months.
A few of the disadvantages are;
- Cost: The initial cost of materials and installation may be much more than the cost of a typical composite shingle installation making a metal roof a non viable choice for some.
- Longevity: A properly installed metal roof will last many years and if you plan on moving soon you may not enjoy the payback from the initial investment unless you build the roof cost in to the price of the building you are selling.
- Improper Installation: Hiring just any contractor to install your metal roof is a bad idea. Experience and attention to detail are of the utmost importance! Many seek out the lowest bid price for installation. This may be a grave mistake and end up costing much more than the cost of a proper installation in the long run. Buyer beware.
The bottom line is that a metal roof has several advantages over composite shingle installations but will cost much more up front. Proper installation is key and not just any contractor should do, nor should you necessarily go with the lowest bid. If you would like to read about the engineering concerns of commercial metal roofing here is a good article. I hope this brief article helps you make better decisions if you are considering installing a metal roof on your home or commercial building.