And in This Corner...Which Type of Corner Joint Is Best for Vinyl Home Windows?

Posted: Apr 15, 2013
Author: G&S Contracting, Inc.

Vinyl is a popular choice of material for frames used in home windows. These frames are typically constructed from straight pieces of extruded vinyl material that is then cut to size and joined.

There are 2 main ways to join pieces of vinyl together when making frames for home windows; mechanical joining and welding. The most common method of mechanical joining is made by making straight cuts and then placing screws through the corners. This method is very simple, fast and cheap, but home windows constructed in this manner have a tendency to leak because there is a small gap between the pieces that often widens with time as the screws work loose. Also this type of join does not create much structural integrity, so these frames are not really very strong.

The other main way of making frames for vinyl home windows is by welding the pieces of material together. This method has two major advantages over mechanical joining:

1. There is no gap between the pieces for rain water and hot/cold air to move through.
2. The join is along the full edge of the material, rather than concentrated in a few spots as is the case with mechanical joining.

Welding of vinyl window frames can either be done chemically or by using heat fusion. Although they may seem more convenient and look similar, chemically welded corner joins are simply not as strong as heat fusion welded joins.

When fitting or replacing home windows it can be tempting to consider using the cheapest option; however, for strength and durability, as well as leak-proofing, there is simply no substitute for fusion welded joins.