Clera Windows + Doors Blog

Principles for Installing Vinyl Windows

The installation of your new vinyl windows is as important to the proper performance of the window as is the entire window manufacturing process. Aside from seal failures, replacement window industry statistics tell us that over 80% of service problems with vinyl windows are the result of poor installation techniques.

The installation of a replacement vinyl window into a wall must provide the following:

  • structural integrity of the vinyl window. A vinyl window should not support any load other than its own weight.

  • air tightness of the interior perimeter of the vinyl window

  • thermal insulation between the vinyl window and the wall

  • minimal condensation on the interior of the glass

  • some allowance for the differential movement between the replacement vinyl window and the wall opening

  • enhanced performance of the vinyl window

Most vinyl window manufacturers publish installation instructions which are often affixed to the new window. Improper installation is usually listed as sufficient grounds for voiding all warranties, so the proper installation of your new vinyl windows is critical.

Vinyl window installation instructions usually cover the following important topics:

  • Care in handling: Be sure to store vinyl windows on a flat surface and in an upright position, to avoid warping. Vinyl windows should not be dropped, nor lifted by the head only. Lifting should be by the side jamb and sill and there should be full support underneath the frame during transportation and installation.

  • Plumb, level and square: Make sure that the rough stud opening for the replacement vinyl window is plumb, level and square. Vinyl windows should not be forced into an opening that is not square or it will twist and warp, causing problems with the operation.

  • Shimming: To ensure that you new vinyl window operates freely, it is necessary to use shims to support the window frame and adjust it so that it is plumb, level and square in the opening. Shims can be made of cedar, vinyl or rubber, so long as it will permanently support the weight of the vinyl window, resist decay and can be screwed into place. Shims should be installed at the quarter points of the sill and sides, at a maximum of 16” apart on the sill and at a maximum of 24” apart on the sides of the vinyl window. They are not normally used at the head of the window. Shims should contact the window frame evenly across its entire width and should be used in pairs with one shim pointing in from the outside and one from the inside.

  • Installation techniques: Do not unlock or open a vinyl window until it is fully blocked and anchored into the opening; be sure to install the new vinyl windows right side up; installation of a drip cap flashing across the top of the vinyl window may be necessary in some circumstances; for smooth operation of the sash, apply silicone to the operating hardware and sash weatherstrip.

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