My skylight is leaking. How do I repair it myself?

Asked By: aimeeloans on Thursday, March 19, 2009
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Answer My skylight is leaking. Is it possible to repair it myself? I am pretty handy at repairs, but I have not tackled a roofing project, yet. If it is a quick fix, can you tell me what tools and steps I need to complete the project? I am hoping to save money on paying labor costs. Thank you, Aimee


This is a question that many DIY home owners have asked me to give advice on as a professional contractor. I am glad that you are asking the question and seeking out an answer.

As you might expect, leaking skylights can have various reasons why they are leaking. In almost all cases, unless there is a defect in the skylight itself, the reason a leak occurs is because of incorrect flashing around the unit. Much of this will depend of if you have a curb mount, which is one that has a frame built first out of lumber and then the skylight actually mounts to the curb, or if you have a unit that mounts directly to the roof.

To demonstrate look at the following photos.

This first one shows the curb that would be framed in and it also shows how the skylight would be mounted over the curb. But before the unit is mounted flashing needs to be installed. The next photo will show you how it should look after the flashing has been installed.

curb mount skylight section

This next one show a completely installed curb mount with the proper type of step flashing on the sides and the wide one piece flashing on the bottom. Notice that the side flashing is a step flashing which means that it is put in using several pieces that overlap each other so that the water can roll off one to another and then off of the roof. This step flashing is then bent so that it mounts on the roof and rolls up onto the curb. The shingles then are installed over the step flashing, but the bottom flashing lays over the shingles. If you look just below the edge of the skylight on the sides, you can see the lines where the step flashing overlaps.

curb mount skylight finished

The picture below shows a deck or roof mount skylight with a smaller attached flashing. I am not crazy about this type of flashing because it is so small that you really need to use a lot of roof cement to seal it up or it will leak. As a rule, I won't install these type because I have had problems with them leaking. In some cases there is enough room to tuck step flashing under the lip of the unit and then over the attached flashing, but it is a bit difficult to do. However some manufactures such as the ones from Anderson Windows, has this feature built in so you get a skylight that fits close to the roof and still allows you to use a step flashing. They even supply the flashing kit.

deck mount skylight with small flashing

Finally this last picture will show you another deck mount skylight with a much wider flashing that though still not as good as the ones that use the step flashing, yet much better then the previous one.

deck mount skylight with wide flashing

The reason I am showing you these is because it is likely that you have one of these types of applications with your skylight.

In most cases, in order to stop the skylight it will involve pulling some shingles around the skylight off of the roof, repairing or replacing the flashing and using an all weather, long lasting roofing cement to seal off any place that is either leaking or looks like it may be prone to start leaking. This would include seams, cracks and nail heads. You may have to peal off any old caulking that has become brittle, because cracks and holes in this old caulking could very well be the source of the leaking.

The first thing you can do though before you remove any shingles, is to take a garden hose up on the roof with you and then have someone be inside the house while you run the water all around and over the skylight. Start with the back side and work around each side and on the bottom. If you both have cell phones, you can use that as walkie-talkies and have the person inside the home tell you when they spot a leak. This is a good way to pinpoint the leaking area. If you are able to find the leak this way then, you can focus on the area more.

The best time of the year to do this is when it is cool because the tar on the back side of the shingles that help stick them together will be less soft and sticky and it will be easier to pry up the shingles and carefully remove them. You want to try to save the shingles if at all possible, especially if you have no extras, so that you can re-install them. 

If you have extra shingles stored away somewhere, then you will be in good shape if any of the shingles break off when you are trying to remove them. You can also take a piece of the shingle to a roofing supplier and try to get it matched up and then buy some to replace the ones that break. It is much easier if you have new, matching shingles, but not necessary as long as you are very careful not to break the existing ones when removing them.

If you are handy and know how to use a hammer, a flat pry bar and a caulking gun, you should have no problem removing the shingles and flashing and fixing the leak. You will want to start with the shingles on the bottom and slide the flat bar under them where the nails are installed, and try to pry loose the nails until you get them to pop up. Yes, you will have to do one nail at a time.

When you are doing this if the shingles pop up but the nails stay in the roof, you need to remember to caulk over the nail holes in the shingles with the same roofing cement mentioned above. The key is to make sure you seal off everywhere you think it is possible for water leak into your home.

Once you have the shingles removed then run the hose test again but this time over the exposed flashing and make sure you work it around slowly while the person inside the house again tells you when a leak occurs. Water can get in through a nail that has popped up, cracked caulking and also around the edges of the flashing. Take your time and keep working until you find the leak.

Once last tip, if you find new shingles but they don't quite match, you can go to an area of the roof that is not easily scene, and remove some of the old shingle and replace them with the new ones and then take the shingles you removed, and use them to install around the skylights to replace the shingles that might break off when removing them.

For more help click on the following link for a great article that will help find and repair the leak.

Repair a Skylight Leak

I hope this helps. Rick

Rick Maselli is Founder and Editor of



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