We're here to Help. Ask the Expert.
RexShowerDoors.com banner image
DIY Center  >> Shower Guide to Success >> Constructing the Opening Download Printable PDF Version


Measuring for your shower door is not difficult. It does, however, require your undivided attention when performing this task. The tools necessary to perform the task are:

  • a level (we suggest levels of 24", 48" and 72" if possible)

  • tape measure

  • pencil or marker

  • paper

  • a square

It’s best to avoid any and all interruptions (phone calls, watching television, etc.) If your eyesight is poor or you're not completely sure how to read a measuring tape, we suggest someone else perform this task.

Measure everything to the 1/16" of an inch. The more precise your measurements, the easier it will be to obtain the correct fit and finish during installation. Be certain to double check your figures and to use a decent quality measuring tape.

  • Complete finish work before measuring! Finish measurements are defined as measurements taken after all tile, marble, granite or solid surface work have been completed. Some people believe they can anticipate finish measurements before this work is completed, but our experience has proven that it fails more often than it succeeds. Be patient, be smart, and have this work complete before measuring.

  • Determine the location of the glass center lines. Begin measuring by drawing lines on all horizontal surfaces where the glass will rest. Start at the sill or the curb area of the shower (where the shower door will be placed). Generally, the glass is installed in the center of the curb. The standard measurement used in the shower door industry is center-line measurements. The use of center-line measurements allows us to correctly determine the glass and metal sizes. Many people are confused by the term center-line. Some feel it’s the center-line of the curb, when in reality it’s simply the center-line of the glass thickness. This means at the time of installation you will have equal amounts of glass or metal on either side of the center-line.

    The center-line of a shower unit can be centered on the curb, or moved to the outside / inside of the curb. If you are using wall mounted hinges, remember that the back plate of the hinge (where it screws to the wall) is wider than where the glass will be located on the sill. Check to make sure your placement of the glass will allow for the back plate to rest completely on the tile, marble, or granite sidewalls for a solid attachment.

    Mark the center of the curb in several places and use a straight edge or level to connect the marks with a line using a marker that can later be washed off. At the left and right ends of this line, you should finish into the vertical wall surfaces. With the use of a level to insure accuracy, set the edge of existing line and continue the line up the vertical or perpendicular surface.

    Should your design include buttress, knee walls or seat areas in line with the curb, you will again encounter additional horizontal surfaces. Using your level, continue these lines on the top of the horizontal surface until you reach the outermost vertical walls of the shower.

  • Determine if you have a "good opening". Frameless enclosures aren’t like the aluminum integrated units that have a great deal of adjustability. Glass sizes must be adjusted accordingly for out of level and or out of plumb conditions. Out of level refers to the orientation along the horizontal plane - whether it's a curb, sill, floor, ceiling or tub deck. Out of plumb refers to the orientation along the vertical plane - walls, step-ups or buttresses. Figure 19 illustrates the concepts of out of level and out of plump.


    Figure 19: In the first image, because the plane along the horizontal axis is not level, the opening is considered out of level. In the 2nd image, the opening is considered out of plumb because the plane along the vertical axis is not level. In the third image, the wall is bowed along the vertical axis.

    When encountering an out of plumb/level condition, a notation must be made to ensure the proper glass sizing. If one places a level on the vertical wall and figures "It's not very far off", or "It's close enough", that person is planning for failure. Measuring precisely is important.

    Always take complete and thorough measurements. Measure and make note of all outages no matter how seemingly insignificant. The reason we ask this is to give the best information possible to make glass sizing decisions. It is always better to provide more information, as opposed to less. Be sure to place a level on all mounting surfaces to note various outages.

    Straight vs. Plumb

    One of the most problematic situations that one can run into is the vertical wall not being straight. A word of caution: Don’t confuse the term straight with the term plumb. A wall doesn't have to be plumb to accommodate a wall mount hinge; however, it does have to be straight. When we refer to straight, the definition would be: A straight edge or level (being used as a straight edge) is touching consistently when placed against the wall that the door will hinge off of, or there are no gaps that exceed 1 /32". We can’t emphasize the importance of the previous statement enough. If the straight edge is touching at the top and bottom and there is a concave (bowed-in) condition that leaves a 1/8" gap in the middle, we need to know! This wall could be plumb and still be a major problem. The reason that this occurs is due to the fact that the hinges operate on pivot points, and the pivot points must align with one another or they will work against each other. Figure 20 illustrates this point.

    Straight or Plumb

    Figure 20: In the first image, the wall is straight and plumb. In the middle image the wall is out of plumb but is still straight. In the third image, the wall is actually plumb but it is not straight due to bowing.

    Measurements and Outages Must Match Up

    A great way to double-check the accuracy of both measurements and outages is to mathematically confirm the information by cross-checking. This process must be done on the job, otherwise the mistake (if there is one) won't be found until it's too late. For example, if a door opening measures 27 ¼" at the bottom, and one wall is plumb with the other wall leaning out of plumb ¼" at the top, the width measurement at the top must be 27 ½". If the measurement doesn’t match the outage, then a mistake has been made and it's time to re-evaluate the information until it adds up properly. If dimensions and outages are not confirmed on the job, there is no chance to re-evaluate the information.


    Figure 21: Measurements and outages must match up.

  • Record your measurements. It is now time to record your measurements on the form(s) we provided. With the proper information, we can fabricate your new shower enclosure to best fit all the conditions you have indicated. Note that for out of square conditions, costs are calculated per cut, thus any panel requiring two cuts will incur two charges. As you can see, it is more cost effective to build the shower correctly from the start. It doesn’t cost any more to build it correctly than it does to build it incorrectly.

Other helpful hints:

  • When measuring any shower that goes to the ceiling with bisecting angles involved, it’s very helpful to have a plumb bob. A plumb bob allows one to get the most accurate measurements possible. After doing the layout on the curb, use the plumb bob to find the bisecting points on the ceiling or the tile lid. This point will be helpful in determining the center-line dimension on the ceiling or tile lid, as well as figuring the outage (if any) on the vertical wall.

  • When measuring buttress heights, place a level horizontally on the buttress with a small portion of the level hanging off. Now a measurement can be taken to the bottom of the level to obtain the buttress height.

  • Place a level on the curb to determine if the curb is pitched properly inward for water drainage. If this problem is detected prior to glass sizing, allowance can be made for the corrective product.

A Word about Neo Angle Construction

When constructing a neo angle shower with buttress walls on end, the door curb should be perpendicular to the buttress walls, hitting them at a 90 degree angle. Figures 22 and 23 illustrate an incorrectly constructed neo angle opening. Figure 24 shows the correct way to build a neo angle shower.


Figure 22: In this example, the door curb incorrectly hits the buttress wall at 45°, not 90°.

When measuring a neo angle shower with a buttress, it is imperative to provide a plan view (overhead) drawing in order to see what the relationship is between the curb and the buttress. This information is important for many reasons. Hinge choice, center-line dimensions and mitering angles on the glass are just a few of these.

Divided Evenly

Figure 23: In this example, the door curb and buttress walls incorrectly divide the angles.

When measuring a neo-angle shower, it's important to confirm the fact that it’s a "true" 135° neo angle. An angle measuring stick is the most certain way to determine any specific angle. There is, however, a way to visually inspect an opening to help assure that it is a true neo angle. As shown in Figure 25, with a true 135° neo angle the tiles are square with the corners of the enclosure and the half tiles at the door curb are all exactly the same size.

Correct Neo

Figure 24: This example shows a correctly constructed neo angle shower. The door curb hits the buttress walls at 90° and the buttress walls are at a 45° angle.

True 135 Not True 135

Figure 25: A true neo angle is shown. The half tiles at the door curb are all the same size.

Figure 26: This example visually illustrates an enclosure that is not a true 135° neo angle. Note that even though the tiles are square with the corners, the half tiles at the door curb differ in size.

Copyright 2017 Rex Glass & Mirror Co., Inc.