Replacing Asphalt Shingles:
Part 2
Installation Details For Professional Results

The old shingles had been stripped and the roof was covered with builder's felt (a.k.a. tar paper).

Click here to read about tearing off the old shingles.

Since I was trying to do this re-roofing job as cheap as possible, I made the eaves starter shingles from some old 3-tab shingles I had saved from a previous roofing job.

I used a utility knife and a straightedge to cut the tabs of these plain black shingles.

As I installed the starter shingles, I applied a bead of roof cement (tar) to the drip-edge.

To avoid having tar squeeze out afterwards, I ran the bead about a half-inch back from the edge.

I nailed the starter shingles so they just barely hung over the drip-edge.

Like ordinary shingles, I drove 4 nails per shingle: One nail about an inch from each end, and the other two nails 12 inches from each end.

To make a row-starter shingle, I placed a shingle upside-down on a work table.

Then I cut the shingle with a sharp utility knife and a speed-square.

For each set of starters, there will be 3 shingles that need to be cut in the center of a tab.

Shingle manufacturers normally make a small cut in the top edge of their shingles to mark the center-point of each tab. I just curled the shingle material up to form a "stop" that I could place my speed-square against.

This makes it easy to cut the row-starter shingles because there is no need to measure anything... all the cuts are either made at one of these 3 points, or at one of the two notches between tabs.

A typical set of "row-starter" shingles. The shingle near the bottom is a full shingle, the other five have been cut.

These are cut on the left side, so I will need to place the cut edges against the left edge of the roof.

The South Side: Left-To-Right

The row-starters after being installed.

The first shingle was a 5/6th shingle, because I used a full shingle for the eave-starter.

After the first group of row-starters were installed, I shingled across the roof until I reached the far side. I used a pneumatic roofing nail gun to fasten the shingles.

When each row approached the end, I had to cut a shingle to reach the right side.

Then I installed another set of starter shingles and ran the rows across again, leaving this stair-step pattern.

A view from farther away.

Note how the orange air hose comes from the other side of the roof. I find it easier to handle the air hose if it's draped over the peak of the roof instead of hanging over the edge on the side I'm working on.

A closer view of the pictures shown above.

As you can see, I need a narrow sliver of shingle to complete the the lowest unfinished row.

I cut a narrow strip of shingle and nailed it to the roof. This shingle was about 2 inches wide.

Actually, the shingle manufacturer instructions warn against doing this, but I did it anyways. I will apply some tar under every end shingle to keep the wind from peeling them up.

I installed another cut shingle on the next row. This shingle was about 8 inches long.

Each final shingle should be about 6 inches longer than the previous, but I measured the required length (instead of assuming), just to be sure.

I let each final shingle overhang the side about 1/8 inch.

OOPS!

When I nailed that last shingle (shown above) I wasn't careful about where I put the nails, and there was a nail head right in the notch of the subsequent shingle.

I didn't make that mistake again.

This problem doesn't happen with architectural shingles because they don't have notches.

To prevent this from leaking, I applied a big gob of tar under both adjacent shingle tabs, and covered the nail head too.

I suppose I could go one step better and apply some shingle granules to the wet tar that was exposed, but I didn't get that extravagant on this garage, especially since this minor flaw is located on the roof overhang. If I was doing this job for somebody else, I would've taken that extra step.

I measured from the lower edge of the roof to the top edge of the last row of shingles.

I did this at both the left and right sides of the roof. The measurements were very close, within 1/8".

I snapped a chalk line where the top edge of the next row of shingles normally should be.

Then I went along the roof and in several places I checked the distance from the top of the each shingle to this line. The measurements were not all the same.

At each end of the row of shingles, my chalk line was about 5-1/8" from the top of the shingles, as it should be.

But in the middle of the row, the top edge of the shingle was 5-5/8" from the chalk line, a half-inch farther than it should be. This meant that the roof had a slight bulge (as viewed from above) and my shingle rows weren't perfectly straight.

That made sense to me, because I could detect a slight angle between adjacent shingles as I worked across the roof.

So I snapped another chalk line one-half inch lower than the first line.

Why make the line LOWER? Because it's okay to make the shingles overlap too much, which will happen at the ends of the row. The shingle exposure on the previous row will be less at the ends, and that's fine. If I used the first chalk line as a layout guide, then the shingles in the middle of the previous row would have too much exposure, and the nails might not be covered.

Why A HALF INCH lower? Because the middle-of-the-row shingles are a half-inch farther from my first chalk line.

I nailed the next row of shingles with the top edges aligned with this new line.

From that point forward my rows of shingles were good and straight, and parallel to an imaginary line that connected the lower corners of the roof. (The actual lower edge of the roof is not straight.)

But that didn't mean the rows were parallel with the peak of the roof.

After I installed a dozen more rows of shingles, I measured down from the peak of the roof to the top edge of the last row.

On this end I measured 49¼ inches.

A Baseline For Measurements:

The plywood at the top didn't form a good clean peak, so I couldn't get accurate measurements by measuring from the edges of the plywood.

However, the trim boards on the side of the roof made a nice clean peak. I just leaned over the edge and located the peak of the trim, and then I drove a nail through the drip-edge aligned with that peak.

Then I placed the end of my tape measure against the nail.

At the other (left) side of the roof, the top edge of the shingle was 50 inches from the peak.

In other words, the shingles on the left side were 3/4" lower than the right side. If I maintained my course, the last row of shingles will be tapered.

I snapped a chalk line that had the proper spacing (5-1/8") on the left side of the roof.

On the right side of the roof, the chalk line was only 4-3/4" from the shingles, a difference of 3/8".

I decided to adjust my shingle rows by HALF of the error. Then I'll do another correction a few rows later.

After I snapped my chalk line (red arrow) for the adjustment row, I fastened the row of shingles so the top edges were on the line.

After a full day's work, the south side was shingled almost to the peak.

I will need two more rows of shingles on this side before I can install the ridge cap shingles. I will also be installing a zinc strip to prevent moss and mildew from growing on the roof.

But first, I had to replace the shingles on the north side of the roof.

After I tore off the shingles and covered the roof with with tar paper, I started shingling from the right-hand side of the roof, using the row-starters I had cut a few days earlier.

I fastened most of the shingles with a roofing nail gun.

I bought this tool a couple of years ago for about $250. Not everybody wants to spend that kind of money on a tool they won't use very often, but nail guns can be rented by the day or week.

My nail gun (Porter-Cable RN175A 7/8-Inch to 1-3/4-Inch Coil Roofing Nailer) can be purchased on Amazon.com for less money.

Installing shingles was simple... until I reached the peak of the roof.

There are some special details for installing shingles at the peak of the roof.

See Part 3: Installation Details At The Peak