Installing skylight windows in your garage can cause problems if not done properly. There are obvious issues that an incorrect installation will result in, so if you intend on putting one or more skylight windows in your garage roof, consider the following possibilities.
Incorrectly fitted windows will leak, but moreso if they are installed in a roof. Consider the type of garage roof you have, before you think about skylight installation. Some roofs are not suited to having holes cut into them and you could end up having to re-roof the whole garage.
Most skylight windows have to have a special waterproof lining around the edges to prevent water, condensation and air creeping into any tiny gaps. The waterproofing has to be fitted correctly and the window has to fit tightly into the gap you create for it. If water seeps past the waterproof layer you will have a build up of fluid which can rot the window, if it is made from wood.
Angled roofs should have a skylight window fitted so that the window opens facing down the roof. This stops any rain coming in if you leave the window open. Avoid the mistake of fitting the window upside down.