ᐅ Glued stair treads are coming loose

Hello everyone, we moved in in the middle of last year and have a steel staircase with wooden steps. The wooden steps were only glued at the time. Now we have the problem that since we moved in, two steps have come loose. The carpenter used Lugato bombenfest as adhesive, a type of assembly adhesive. Can you recommend something better?

The steps have been oiled twice and the glued area was not scored or treated in any way. (We had noticed this with the first step.)

After the first step came loose, we reglued it. The second step is not completely detached yet but already loose. The adhesive sticks to the steel but not to the wood. What would you recommend now? I have attached pictures of the staircase construction. Of course, it is possible to screw the steps in place. However, we did not want to see screws from underneath. If we decide to screw them in now, is it possible to drill from below while keeping the steps in place?

Old painter’s saying: nothing sticks to oil. That’s the first problem.
And wood expands and contracts. Metal doesn’t. This is a very, very unfavorable combination when it comes to the durability of the joint. Who recommended this to you?

Yes, I suspect that now as well. I wasn’t present when the steps were glued. I had actually thought they would be sanded down.

We did say that we wanted to glue them. I know that method from my parents. The frame is identical, but the steps are not oiled. It has held up for 15 years. The carpenter did not object and provided everything needed for the attachment.
With the first loose step, I noticed that about half a millimeter (0.02 inches) of "wood material" remained on the adhesive. This oil/wood residue then separated from the step. So this is the weak point, as you also mentioned.

Are there adhesive options that might penetrate deeper into the wood? Or is sanding the adhesive surface on the wood sufficient?

If wood was attached, the adhesive is so strong that it tears the wood fibers. In this case, poor adhesion due to the oil is not the only issue. Since wood naturally moves—especially with oiled, that is, exposed surfaces—it tends to come loose more easily at the oiled spots and tears off in areas with less oil. This cannot be avoided. Screws would then cause the steps to crack.
Was the staircase at your parents’ place probably painted?

At my parents’ place, I’m not entirely sure. If I remember correctly, we have beech wood steps that were oiled twice to achieve the current color.

At my parents’ house, I don’t know for sure. They are not painted. I would rather say they are oiled. The staircase was heavily used by three children, with jumping down, sliding, and all that comes with it. Everything is still firmly intact like new.

For us, a friend who admittedly comes down the stairs in a strange way (jumping), and a large, sturdy tiler are enough to loosen the steps.

Myrna_Loy schrieb:

If wood was attached, then the adhesive is so strong that it tears out the wood fibers. Then the poor adhesion caused by the oil is not the only problem.

I will try to loosen the step later and send a picture of it. Real wood fibers did not remain attached back then.

Does it look more like oak?