Underlayment seam telegraphing; what is it and why does it happen? Simply put, underlayment seam telegraphing is the transference of a substrate profile outward/upward into the top or finish layer of floorcovering. This is usually a condition that is visible in vinyl floorcovering or resilient type products. Why does it happen? The causes are widespread depending on whom you are talking to. But one thing is for sure; if the telegraphing was there when you left the job, chances are it's underlayment prep related.

It's not typically covered by the underlayment manufacture, and why is that? Because the underlayment manufacturer has no control of the installation. If you had drywall installed and the tape showed through or telegraphed showing unsightly lines would you call the drywall manufacture and call foul? No, you would call the installer.

What you see in the following photographs is where one decision made by the installer created unacceptable visual concerns for the customer. Photos A, B and C are of underlayment seams telegraphing. Can you tell from the photos what the possible problem is?

You Make the Call!

Without cutting the floor how can you ascertain the cause of the problem? Look at everything else relating to the job site. Using the metal bar tap test, tap on, around and across the underlament seams and listen for hollow spots. This will tell you if your underlayment is tight to the subfloor or if your floorcovering is not adhered to the underlayment. In most cases, unless you're very careful, while removing your sample (sandwich) you destroy the sample to the point where it is not representative of the problem.

Photo D shows what? An underlayment staple crown pushing upward or out; does this help you as you try to surmise the situation? If you are able go into the basement and look underneath your problem area. Sometimes you see what's going on a little clearer when you get a different angle.

Photo E shows what was visible from beneath, it's a great way to see the number of fasteners used both at the seams and in the field of the underlayment. But only if they are sticking through. But wait a minute, are the staples supposed to stick all the way through? And what kind of staples are they? Chisel points, which are recommended by underlayment manufacturers as an acceptable fastener, but is that the only one? No, divergent point (or saw tooth) fasteners are also recommended. I personally like divergent fasteners because what you see in Photo E and the close-up photo, Photo F, is less likely to happen, especially on an OSB type subfloor.

When your fasteners blow through the subfloor like this, it is highly improbable that they are going to stay put! Most likely with traffic on the floor and expansion/contraction of the home (on a seasonal basis) they will move upward trying to work themselves out. I have only touched the surface of underlayment telegraphing; there is a lot more cause and effect on this subject matter. It is sufficed to say that being well versed with your job site conditions and products you're installing is still your best insurance for a successful installation. Thanks again for reading "You Make the Call." Have a great day!