Roofhelp.com - How To Replace An Asphalt Shingle

If you aren't real familiar with shingles, you may want to visit http://www.roofhelp.com/3tabpage.htm to familiarize yourself with the anatomy of a shingle.
	Shingles are installed in overlapping fashion in order to attain double thickness as shown in the picture to the left. Because this is done, and because the width of the overlap is wider than the width of the exposure, you end up with two sets of nails driven through the same shingle – the nails holding the shingle you want to replace, and those holding the shingles in the course above it. This means that when you’re replacing a shingle, you aren’t only dealing with the shingle you’re replacing but also the shingles in the two courses directly above it.
	For instance, let’s say you want to replace the red shingle in the picture to the left. In order to do this, you'll not only need to pull the nails holding the red shingle but also the nails holding the blue shingle. As you can see, the nails holding the blue shingle also penetrate the top edge of the red shingle. So what does the green shingle have to do with it? You have the lift the tabs of the green shingle in order to remove the nails from the blue shingle.
	Let's go through the steps of how to replace the red shingle seen at the left.
	The dashed line represents the outline of the shingle we want to replace. The red circles represent the approximate locations of the nails holding the red shingle.
	In this picture, the blue dashed lines are outlining the shingles in the course (or row) above the shingle we want to replace. The blue circles are the nails holding the blue shingles. See how they are located within the outline of the red shingle? This is showing you that these nails also penetrate the red shingle and will have to be removed in order to properly replace the red shingle.
	Let’s start at the top and work our way down. First, break the tabs loose on all the shingles that we’re dealing with – the red, the blue, and the green. Use a flat nail bar. It's best to do this early in the morning when it's cool and when the sun hasn't yet hit the rooftop.
	Next, lift up the green tabs and slide the nail bar underneath the blue tabs and remove the nails holding the blue shingles.
	Now you want to lift up the blue tabs and slide the nail bar under the red tabs and remove the nails holding the red shingle.
	Carefully slide the red shingle out. This is similar to how it will look.
	Before you replace the shingle, it’s a good idea to take a dab asphalt cement caulking and cover the nail holes of the shingle you just removed. These holes are indicate by the red triangle.
	Now slide a new shingle up under the blue shingle. You may have to work it a bit by wiggling it back and forth in order to get it to set right. Nail it in the locations shown.
	Next you need to reinstall the nails you took out of the blue shingle. You can nail them back into their original hole. RoofHelp strongly recommends that you put a dab of asphalt cement caulking over the old hole before driving the nail back into it. This will help seal the hole.
	You’re almost done. The last thing you want to do is place a dab of asphalt cement caulking UNDER the corner of each tab that you broke loose. This is indicated by the little red triangles. This is important because you broke the seal when lifting the tabs so they’ll never hold with the same strength as the original seal. With the asphalt cement caulking under them, the tabs will hold properly.