I have experienced numerous problems with the T-molding that I have purchased for my floating engineered hardwood floors: defective staining, splits in the ends of the molding, variation in width of molding sold for the same purpose,... This thread begins by addressing one such problem: the base of the T-molding is too short to reach the sub-floor.

I have finished with installation of 15 mm thick Kahrs engineered click-and-lock flooring. What remains is installation of the various transition strips. From the supplier of the Kahrs flooring strips, I ordered T-molding designed for the 15 mm thick flooring. I received T-molding that has an acceptable width and staining but the base of the T-molding (the vertical part of the "T") is only 12.5 mm tall. It won't reach to the sub-floor. I checked to make sure that I received the correct product. It was labeled with a UPC/barcode indicating that this T-molding was indeed designed for 14/15 mm Kahrs flooring.

One flooring contractor I discussed this with suggested that perhaps the T-molding was designed to be installed in a metal track. If so, then why didn't the flooring supplier mention such a track and why didn't they offer such a track on their website?

On another website, one installer noted that T-molding was frequently too short to reach the floor. To solve this problem he used shims. This is what I am now doing: gluing a 1/8" strip of wood to the base of the T-molding. Why was the T-molding designed to have a base of less than 15 mm?

This is pretty common. We always do just what you are doing and that is to put a thin strip for the tt-molding to rest on and to nail to.

Thanks for the reply. I phoned Kahrs and the support person there said that they intentionally cut short the base of the T-molding. Kahrs suggests that the construction adhesive should fill in the 3 mm gap.

If this is the case, my only remaining question is what happens if someone steps on the T-molding? Will the construction adhesive support the weight or will the T-molding be pressed down below the top of the floor and be subject to stresses that may crack an arm off of the molding?

"Will the construction adhesive support the weight or will the T-molding be pressed down below the top of the floor and be subject to stresses that may crack an arm off of the molding?"


only if its Kirstie Allie...

As said, it's common. But I would say it's common so the manufacturer can cross reference that same specie t- moulding for different product thicknesses.

The problem with filling the gap with adhesive...... One of the functions of a t-moulding is to allow proper expansion. Your not going to maintain proper expansion trying to fill the void of the leg. The adhesive just fills the expansion space.

I do like Rhodes says, and fir up the leg with a strip.

Thank you all for your prompt and informative replies.

If you fill up the gap with a shim then the layer of adhesive must be pretty thin. Is that right? A quarter inch diameter bead?

I run a bead on the subfloor, and a bead on the leg. I may take some heat on this...but I shoot 23 ga. wire to hold it secure also, ( I don't believe 23ga. will alter movement, and they're not noticable).

If I'm transitioning to tile....I tape off the tile, and fill the tile side of the "T", solid with clear 100% silicone. This also camoflauges the variation at the tile.

Over a wood subfloor...I avoid topnailing the leg with a larger gauge, ( don't like topnails, unless covered by base, etc.)

I thought I would give it a try with the approach recommended by Kahrs. I applied to the gypcrete sub-floor a very thick (1/2 inch) bead of Liquid Nails "Heavy Duty Interior and Exterior Construction Adhesive". I then put the T-molding (without any shim) in place and weighted it down on each end with some surplus tiles. Twenty hours later I pushed on the T-molding and found that it moved with minor pressure. When I lifted up the T-molding (again, this took minimal force) I found that the Liquid Nails was still very maleable and friable like caulk.

So that didn't work.

Now I am testing another sample with a shim glued to the base of the "T" and only a quarter inch bead of Liquid Nails. I will report the results in 24 hours. But I suspect I will find that I am using the wrong construction adhesive. Any other suggestions in addition to those offered by Floorologist above (i.e. apply a bead on the leg of the T as well as a bead on the subfloor)?

Thanks, Bob

Over concrete you may want to use a better grade adhesive that is moisture cured like PL Premium. I install the transition areas so I and glue the back side of the T to the tiles edge. Better support, just make sure you weight it down good or they will not set all the way.

Thanks. I am googling for "best construction adhesive" and I see a variety of recommendations:

"PL 200 or PL 400";
"Loctite PL Premium Polyurethane Constructition Adhesive";
"Bostik's Best" (moisture-cured urethane);
"Sika Construction Adhesive" (polyurethane);
Henkel PL Premium Polyurthane;
Gorilla glue

Does anyone know of a systematic review of such adhesives?

Will any of them hold wood to concrete (or gypcrete in my case) long-term?

I just learned that Loctite/LePage/Henkel are now the same company. That is why "PL Premium" moisture-cured polyurethane construction adhesive is marketed under all 3 names. The Loctite brand is available at Home Despot.

But will it keep wood bonded to concrete (or gypcrete) for several years?

Yes the Pl Premium will bond but gypcrete is notoriously dusty. Make sure you work it into the surface and also the transition strip.

For bonding....it helps to scarify the concrete with open coat sandpaper. Then vacume, wipe down clean with damp rag, let dry.

Good point about the sand paper Howard. Especially if there is Lord knows what on the surface. Using a damp rag to clean up the dust is also excellent. But the PL Premium is a moisture cure urethane so if the surface is slightly damp it sticks better. It cannot however be wet, just damp. I used to stick carpet tackstrip down on concrete and ceramic tile like that, works wonderful and fast.

Doesn't feel right to me applying adhesive to a damp slab, just something about it. Besides the adhesive states moisture cured, not moisture stick better Infact I believe they all state for the concrete to be dry.