Adding a Metal Roof

Homestead Improvements — Roofing

Adding a Metal Roof

I built my house in the 90’s, and my roof is showing its age. I am finding a lot of asphalt particles in the gutter. And when I look at the roof, I see the shingles starting to curl at the corner, so I need a new roof. Luckily there are no leaks yet, so there is a little time to work on it. When I start looking at all the different types of roofing material out there—asphalt, cement, tile, metal, rubber and even fiberglass—I am finding different advantages to each of them, from cost, life expectancy, weight and style of the roof.

I knew I did not want to go asphalt again for several reasons. First I will be 50 this year and while I don’t mind roofing, the life expectancy of an asphalt roof is anywhere between 15 and 25 years, so this means when I am 65 to 75 it will need replacing. I would not want to do it myself at that time, not to mention the cost of paying someone else to put another roof on. Secondly, I have a nice greenhouse and several raised beds. And I would like to collect the water off the roof (in food safe drums) and use this to water everything. The thought of eating something that was grown with water with asphalt in it does not appeal to me. And thirdly, I wanted a roof where I did not have to go out in the middle of winter and use a roof rake to take off the snow to prevent ice dams; usually I have to do this on the coldest days, not always the most fun.

So after asphalt roofing was eliminated, I considered cement and tile. These have a great life expectancy. I could put these on and never worry about it again, but there were two things I didn’t like about these options: first is the cost, as these are some of the most expensive roofing material out there; and secondly, the weight of these materials is much greater than the others. And while my house could probably handle the weight, it would be harder on the house than other types.

Rubber was an interesting idea. I have seen it on flat roofs, but they normally cover the rubber with stone to protect the rubber. Because my house has a 4/12 pitch (4 inches of rise for every 12 inches of length) the stone would not stay on the roof by itself. Since I thought having the bare rubber on the roof would not be a good thing (falling branches could cut the material causing a leak), this option was not for me.

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This left me with two options: fiberglass or metal. Both of these would do everything I wanted. They will outlast me. You could get them in a variety of colors and styles (even looking like shingles if you wish). I chose to go with the metal roofing for the following reasons: The metal roofing has a 75-year paint warranty before it even starts to rust. And if I am around then, I am doing well. Secondly, the weight of the metal roofing is one-third of the asphalt shingles, so this will make it easier on the house. Thirdly, you can get sheets of metal roofing (the option I went with instead of the shingle look style) that is the length of the roof. This means there are no seams on the house for water to back up and cause an ice dam and damage the house. These three options could be said of the fiberglass roofing also. But what sold me on the metal roofing over the shingles was that I could buy solar panels that are made to fit inside the ridges of the metal roofing. I could do all the work without having to buy any special tools. And finally, my house insurance company will give me a break on my insurance with a metal roof on the house.

Since my house only has one layer of roofing on it, I could just put the metal over the top of the roof and be done with it. This is the easiest and the quickest option, but I do not think it is the best option. The roof is already starting to curl on the corners, and over time, this will dent the roof and you will see it from the ground (unless the solar panels cover it). I decided to tear off all the old roofing and take off the tar paper, and go down to the bare wood. This will be the best over time, and if there was any damage from the bad roofing, I could fix it before it got worse.

When you plan on doing this work, try to do it on a day where there is no rain forecast for a few days after (as a buffer if you run into problems) and a cool day, as when the sun hits the roof and reflects back at you, it gets hot up there fast. I recruited family and friends to help with the roof (10 people total), not to go on the roof but to help pick up the shingles and paper as they fall. A coworker helped me tear the roof off. When one worked the other picked up the pieces and threw it on the ground that we covered with tarps to help collect any nails and small pieces. My house has a 16 square roof (a square is 100 square feet). It took the two of us 2.5 hours to tear off the back half of the house. When you start to tear off the roofing, work from the peak down to the edge of the roof. The shingles “pop” up easier and often take the surrounding shingles at the same time, making it the quickest and easiest way to do this.

We started at sunrise at 6 a.m., so by noon we were done, just in time for the friends and family to come over and pick up the mess we left for them. My enclosed trailer is 7-feet wide by 12-feet long; this was the back half of the roof.

Once the roof is down to the bare wood, it is time to put on the roofing paper. You have several choices: you could use tar paper (15- or 30-pound paper or several types of synthetic roofing paper). I chose a synthetic paper that is rated the same as the 30-pound tar paper. It is not only a lot lighter to carry, but is 5-feet wide. This width is nice, and not only will it go on faster, but it covers the 4-foot-wide OSB roofing panels with a one-foot overhang. Plus, it is clearly marked where to place the staples to hold it in place (where the dots are), and it has a line on each side showing how much the next layer should overlap it to preventing leaks. While I was laying the underlayment out, I went over the vents and came back later to cut and tuck them in.

A lot of people think that having a metal roof is loud, especially during a rain or hail storm; this is because of the “drum” effect of the metal when something hits it, it deflects and bounces back, the vibration is like when you hit a drum. Some drummers put towels inside the drum to change and mute the sound. I found two options to do this: one is called a roof blanket, but I chose the other option called “Fan-Board” insulation. This is •-inch thick, 4-feet wide and it comes in 52-foot lengths, bending one way, and then another, creating the “fan-look.” It adds a little more insulation to the roof (R value of 1), but it completely stops the drum effect. What it also does is provide a lot of support for the metal roof when you walk on it. And it takes out any bumps from the roof so the roofing will lay flat and look nicer longer. I used the same •-inch staples on both the underlayment and the fan-board. I started from the bottom and worked my way up.

Once I had the fan board insulation up, we lifted up the metal panels and screwed them in place. The screws have little rubber washer on them to make them waterproof. But I also put on 50-year clear silicon over each one, simply because I figured it won’t hurt. When you place the first panel, take your time to get it as perfectly aligned with the roof as you can. Any mistakes here could be multiplied as you get to the end of the roof. The second panel slides over the first one, creating a water-tight seal. When I measured for the roof, I left a 3-inch gap from the peak on purpose to leave room for a roof vent at the peak, and the top trim piece covers 6 inches per side, easily covering any gap left behind.

Metal Roofing
The roofing valley, the only seam on a metal roof. Right: The finished product.

This back side of the house was the easy side, a simple straight roof. The underlayment, insulation and metal roofing took us about three hours to do.

I think it turned out pretty well. I had to trim a little in the corner where the house meets the greenhouse. But other than that it was a good day’s work.

The next weekend, we did the same to the front half of the house. Tearing off the old roofing, getting down to the bare wood, which took three hours to do. I decided to eliminate the small skylight in the bathroom, and when I took the roofing off, I saw a little water damage around the corners. I framed it in and put a piece of 3/4 OSB to cover the hole to match the rest of the roof.

Once the underlayment and the fan board insulation were installed on the front half of the roof, it was time to install the valley on both sides. When you order the roofing, I had to make a choice between getting the standard residential valley or the commercial valley—the difference is going from 12 inches per side to 20 inches per side. I chose the commercial one because I wanted the extra protection and it was worth the extra $30 to me. The valley is the only place on the roof that has a seam in it, they come in 10-foot sections and I needed 18 total feet (per side).

Putting the metal roofing on is very similar to the backside, except you have to trim each piece that goes in the valley. I chose to cut the metal as close as I could get middle ridge of the valley, and before I installed each piece I put down “Bituminous rubber flashing tape” to help seal it in this area.

I think the house turned out pretty well. It is nice and quiet, not only during the rain, but we have had hail recently and it is as quiet as the old asphalt roofing was.

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