This article is going to be about replacing an old sliding glass door with a modern Vinyl frame sliding glass door. If you currently have french doors and you want to replace them with sliding doors, or vise versa, future articles will cover that topic.

The first thing we have to do is measure for the replacement door. You want to measure across the bottom, center, and top of the existing door frame to find the narrowest dimension. Start outside and measure at the point where the old door frame stops and the exterior material starts. That material can be stucco, siding, or brick. Measure across in the 3 places: bottom, center, and top. Record the smallest dimension. Then go inside and do the same thing. You want to measure where the frame ends and the drywall, plaster, or sheetrock begins. Take all six measurements, find the narrowest one, and deduct 3/4". That is the width of the new door. Now, when you measure the height, you can do it just on the outside. Measure the left, center, and right side from the ground where the bottom track sits, up to the top where the old frame ends and the exterior material begins. Take the narrowest dimension and deduct 1/2". That is your height of the new door. Then, determine which side the sliding panel should be on. The fixed panel is designated by the letter "O", and the slider is an "X". In most areas of the country, you call it out by looking at the door from outside and reading left to right. So, if you were outside looking at your door, and you want the sliding panel to close to the right wall, you would ask for an "OX". However, because i have recently discovered that not all parts of the country do it this way, my suggestion is to ask the dealer how they read the opening before placing your order.

Next, you have to decide whether you want a retrofit frame or a replacement frame. If the old frame is flush with the exterior material, such as in the case of stucco, then you want to get the retrofit frame, which comes with the outside fin. That will eliminate the need to trim the outside. If you have brick or siding surrounding the opening, then you need to get a replacement frame and trim the outside yourself. You can use wood, vinyl, or other composite materials available in most major hardware store chains. You also need to measure the depth of the old frame. The majority of vinyl replacement doors have a frame depth of 4 3/4". Most door openings, when framed, have a depth of 5 1/2" to the innermost surface of the wall, whether it's drywall, plaster, or whatever else. Therefore, when you install the new door, you will need to add some sort of trim product to build the inside of the door frame so it is flush with the wall surface. We sell vinyl extrusions specifically for this purpose. It's a two piece system that allows you to bring the frame flush with the wall, then apply the molding to the wall and door frame to finish it. Pictures and descriptions of the products are available by going to http://www.how-to-install-windows.com and clicking on "shop".

You want to be sure and order all of the materials you will need to do the job at the same time that you order the replacement door. That way, when the new door comes in 2 to 4 weeks later, you will have everything ready to do the job. In addition to any trim needed, you are also going to need caulk, a roll of R-13 Insulation, liquid nails for the track, 4" deck screws, shims, dust masks, and safety glasses. Once the new door arrives, it will be time to take out the old door. That will be our topic in next week's article.

John Rocco has been installing replacement windows since 1978. To learn more, visit How To Install Windows