Metal versus Traditional Shingle Roof

4powells said:

1. How do the costs of installing a metal roof compare to using traditional asphalt shingles?
2. How do the lifetimes of each product compare?
3. How much extra/less preparation is needed to install a metal roof (versus the shingles)
4. Having never spent any time inside a house with a metal roof, is there any aesthetic value inside the house? I.e. can you hear rain tap tap tapping on the roof?

Click to expand...

As an installer of metal roofing, I think I can contibute a bit of insight.

First, "Metal" covers a lot of ground. The metal can be steel, galvalume, aluminum, copper, terne, and zinc. The shape can be in form of long panels (as in standing seam), wide panels (as in bermuda style), strongly profiled panels (as in spanish-look, etc), shingles (designed to look like shake, slate, 3-tab, etc.), and custom-formed.

Secondly, the finish on the metal varies. Steel, galvalume and aluminum are generally prepainted (again, a variety of paint systems are available), while copper, terne and zinc are usually allowed to oxidize naturally.

Thirdly, depending on which combination of features you like, the cost can be as little at $3.oo per sq.ft. installed up to $15.00 per sq.ft. Of course, at the low end, you have relatively low-quality finish, metal and installation method, whereas at the high end you got an architectural wonder.

Given these remarks, I can give you some general guidelines:

1- Metal roofs will almost always be more expensive than conventional shingle roofs. However, since the installer determines the quality of the final product, a good roofer can make even cheap materials perform well (but you will pay for his expertise), while a bad roofer will make a sieve of the best materials. So my usual response is for you to find the best roofer you can afford in your area, and let them suggest the materials thery are comfortable with.

2- roof lifetimes are like promises, a lot depends on which fingers and toes were crossed when the promises were made. With conventional roofing, we've seen 25-year shingle fail in as little as 10 years, and we've seen the same type last over 25. Some cheap metal will need repainting in as little as 10 years, and will be perforated in 25 (without maintenance), but others will last easily over 100 years without major work. Also, don't forget that a roof is like a chain - it fails at its weakest part. If a roof depends on caulking to be weather-proof, and the caulking has a life of (say) 5-years, then you have a five-year roof. Again, it is your roofer who for the most part determines whether the roof system lasts as long as it should.

3- in both cases, the roof must be properly prepared to accept the new roof covering. You can hide a lot of stuff under a new metal roof (especially if it is on strapping), but the compromises you make will catch up to you, sooner or later. If you are investing in a quality covering, spend the money to give it a good foundation. Each system will require its own type of preparation, so again, a knowledgeable and capable roofer is your best protection.

4- depends on the type of product and the installation method. Some metal roofs are no noisier than asphalt shingles, while others "contribute" their special ambiance.

So as you continue to develop your ideas for your dream home, think about what attributes are most important to you, what look you want to achieve, what durability you want to have, and then find the best roofer in your area to discuss your ideas with. Let them help you figure out which materials meet your needs the best.

I wish you good luck with your dream. In our own work, we often meet or exceed the homeowner's expectations, but we are specialized and only take on those clients where we feel we can deliver on their expectations. At the same time, we pay our craftsmen well, and the end result is expensive, unless the homeowners take an "investment" approach to this expenditure.

Hidden fasteners...

Teetorbilt said:

None hauled to the dump here! I'll trust direct connect way before a bunch of clips, too much potential for failure.

Click to expand...

Teetor, did you know that some models of standing seam actually have a nailing flange that is hidden under the next panel - so you get direct connection, without the dangers of surface penetration. These are more expensive than the screw-through systems, but in my opinion they are much better. In our area, we've removed a few of the screw-through systems, but I have yet to replace a hidden-fastener system.

As for the clip systems, it depends on the quality of the system. Some clips are cheaply made and rust away, while others are as durable as the roofing material. Again, it matters whether there is true ventilation under the metal (ie, air flow from bottom to top) as opposed to horizontal air cells, which to my mind do NOT form ventilation as there is no provision for air movement by convection.

Teetorbilt said:

griz, Since the hurricanes I am becoming a metal roofing expert. I have been hitting every source available. Has any value been attached to the wear of the metal as it expands and contracts? In most places that would be a cycle of 280 days a yr.

Click to expand...

The expansion and contraction of metal as a factor in metal fatique is somewhat overblown. Take for example a steel panel that is 24 inches wide. Assuming the worst-case scenario for expansion from the coldest temperature (say, -40F) to the hottest temperature (say 180F), you get a difference of 220F, which multiplied by the expansion coefficient of iron (0.00000661 /F) and the length (24") gives you a maximum expansion of about 0.034 inches or just a little over 1/32". So laterally, the amount of movement is minimal. On a long panel of 20ft., you will get a maximum difference of about 0.35 inches over that same temperature interval. If the panels are installed over strapping, the the metal will either pull or push on the lower and upper horizontal strappings, causing them to rock a little.

Since most metal panels also have longitudinal ridge, bends, or curves formed into the panel, these will usually take up most of the expansion and contraction in the horizontal plane, and the strapping will take up the movement in the vertical plane. If the panels are affixed directly to the substrate, then some manufacturers punch elongated nailing holes in the concealed nailing flange and instruct the installer not to overdrive the nails to allow the metal to move (same concept as for siding).

The oil-canning that one sees at times is usually seen on flat sections that do not have any ridge or bend to allow the metal to absorb the expansion stress. However, the amount of movement that reveals itself as oilcanning is usually too little to cause any kind of metal fatigue. So I cannot see the expansion or contraction phenomenon contributing to the "wear" of the metal.