Question

Hello Rabbi,
I used the vacation with the kids to build a treehouse in the grove near the house…
But the part attached to the tree was built in two stages: first I attached a beam to the tree, and only afterward did I attach the floor of the house to the beam.
My question is whether this counts as secondary sides, since it is attached.
I looked a bit into the Talmudic passage, but the definition did not come out clearly for me, since a peg stuck into a tree is indeed defined as sides, meaning that attachment does not make it one entity with it (so that it would be considered like the tree itself). So perhaps one can infer that attachment to the sides, even if it is really attached, would indeed be considered secondary sides; or perhaps only at the first stage is it considered sides, and afterward anything actually attached is considered the sides themselves.
(P.S. It is hard to determine whether it would stand without the support of the tree.)
I would be happy for an answer with an explanation.
Thank you very much.