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  • The Flooring Doctor, David Newman

The Reason Behind T-Moldings


Do you have gaps between your floor planks? This is for you…

Back in the late 90’s, when laminate flooring was being introduced to the United States, we (flooring consultants) were instructed on the characteristics and properties of these flooring products and installation at seminars and through articles published around the same time. One thing we learned was that floating floor installations create a condition where the entire installation reacts as a monolithic unit with more influence, or force, being created by the larger areas compared to the smaller areas.

A large mass, such as a living room, dining room, or kitchen (which all flow or connect), creates a greater force than a smaller mass, such as a bedroom. When these areas are located at either end of a thin hallway, they cause great stress to the hall area which will often result in gaps.

Examples of these gaps are depicted in the photos below of an installation job I inspected. This installation revealed gaps along perimeter walls to the left and right sides of the installation, as well as along one interior dining room wall. There were also gaps between planks in the hall area at or near the doorways. The overall span ( no T moldings were used) measured over 52' from one perimeter wall to the other. Note the percentage of expansion or contraction stays the same but the mass changes.

For example, let's say one plank shrinks 1/64", which would be no big deal for a nailed or glued down floor, but here there are 78 planks across the widest span. This total span would then shrink about 1 1/4", which in this case resulted in gaps between planks as described above. Most laminate flooring manufacturers require just 1/4" of expansion space along vertical abutments (walls, cabinets, etc.), which equals to 1/2" combined to 2 perimeter walls. If these same planks were to expand just 1/64" per plank, totaling about 1 1/4" in growth, minus the expansion space would leave 3/4" of material with nowhere to go, which would create buckling. So how do you avoid this? The answer is T moldings.

T moldings help to isolate these large areas, or masses, so that their influence is confined. In the example shown below, if T moldings were installed at the doorways into the bedrooms, then the largest span would be reduced. For example, Let's say it's now a 20' span, equating to 30 planks, using these same shrinkage factors resulting in a total amount of less than 1/2". This 1/64" change in dimension could happen with the slightest change in relative humidity and/or temperature.

In this photo you can see the long span through this floated flooring installation, viewed from the bedroom at the end of the hall, extending through to the living room at the back of the photo.

Here you can see the 7/16" gap at the doorway into this far bedroom.

This photo shows the gap along the wall in this same bedroom.

Here is an image of the bedroom doorway, the gap in the flooring, and the lack of any T molding installed. These gaps did not show up until a few months after installation.


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