Life expectancy of metal roof

I made a 4 point inspection today on a home with a metal roof. The home is 55 years old and the roof is original.

Most of the sites I see indicate that a metal roof should last between 30 and 50 years but some say the metal roof can last the lifetime of the home. I need to be able to state the remaining life of the roof.

The roof looks good in general. It is obviously old but looks to be in good condition. No signs of leakage or rust. The customer says that her husband recoats it every several years.

How would you estimate the remaining life? I was thinking about saying that it appears to have approximately 10 years left. Any suggestions?

I would describe it as a roof that is at or approaching the end of its normal service life. Expect to need replacement of roof covering at any time.
If the fasteners are getting weak or loose, one big wind could change everything.

John Kogel

If it is 55 YO then it has lead washer nails which can be problematic due to various factors immediately after installation say nothing about 55 years. Sulfuric acid rain (coal plants) will cause lead sulfide and deterioration also. Metal roofing can fail where sheets weather lap including the ridge cap. You may not always be able to see the corrosion. I’d question whether 55 YO nails into sheathing were still doing an adequate job or not. If you are not familiar with evaluating and installing metal roofing IMHO you need to refer to a qualified roofer. Maybe 30 years without maintenance, unlikely 50 and they are at 55. Borrowed time. This is just from my own 35 years experience in the acid belt. I do have some 40 year old Wheeling that looks as good as new on the other hand.

Put down ten years and you just bought that roof if it doesnt last that long. This may be one of those instances where a licensed roofer should be writing this report.

I inspected a metal roof that was installed in 1926 when the house was built (83 years old) a few months ago. It looked brand new. The old lady selling the house was born there (right in the house) and said they had never done any maintenance to it. Amazing. Almost looked new.

Short Answer: Estimating the life expectancy is outside the scope of a home inspection. I assume this is for Insurance?

I know there are metal roofs that have a 100 year warranty, an have seen them installed. (good luck collecting on them in 99 years) As mentioned above, there are so many factors other than the condition of the steel. If it is recoated every few years, it will add serious life to the STEEL, assuming the fasteners hold.

Michael, you are correct that estimating life is out the scope of a home inspection. This was a Four Point inspection which you may not have in MI. You have to estimate the age of the roof and give some estimation of remaining life. I try to err on the conservative side. I also reroofed a house back in the 1970’s. I had to remove the old roofing of which part of it was a metal roof. When I pulled the old roof off, it was stamped on the back “Guaranteed until 1926”. I don’t know the original guarantee, but that was 50 years past the end of the warranty! I’m willing to bet that if the rest of the roof had been the same material, the roof would still be going.

This roof looked good from the top and the bottom. It seemed to be adequately secured. Of course if we get another tropical storm or hurricane, all bets are off (as would apply to shingles, tile, etc.).

Thanks for the input guys.

Don’t go out on a limb !!
Roof was ‘functioning as intended’.
Don’t estimate the lifespan, out of your scope of knowledge. Refer to qualified roofer.

I quote the estimated life expectancy for that type of roof only. I once quoted 20 years for a 100 year old roof. The owners had been recoating it every few years and it was already 100 years old. No visible corrosion on the underside(over battens). They Agent called and said, “A roof cannot last 100 years.” I suggested he tell it to the roof because it was still there. There are too many factors to predict when a roof will fail. I can only recomend what the Life expectancy should be. ie., three tab 15 years, roll roofing 10 years, dimensional shingles, 30 years, metal roof 50 years. I hope this helps.