Hi all,

First time posting. I am replacing a lattice screen that was previously fastened onto the top of my deck rail using many L brackets and no vertical support from the deck rail posts. The lattice screen is located at a corner of the deck and screens the hot tub. There are grape vines growing on it that can get very leafy and very heavy with fruit. The leaves also catch the wind, hence the previous failure. To ensure this screen does not fail, I am fastening 2x4s to the outside of the 4x4 deck railing posts and having the 2x4 extend vertically 4 feet past the deck railing. I will then fasten 1x1/2 Cedar square lattice to the front of the 2x4 and resting the edge of the lattice along the top of the railing. I will then fasten 2x4s mounted to the top of the deck railing to the front of the lattice, essentially creating a sandwich of 2x4, lattice, 2x4 with approximately 8 feet between these vertical supports. I like the idea of how much support this will provide the lattice including for when the neighbourhood raccoon family climbs up to eat the grapes. Having the edge of the lattice rest on the top of the railing also provide me additional support, including the possibility of fastening the lattice directly into the top of the railing.

What I would like to consider is having the 2x4s extend about 8-12 inches above the top of the lattice creating a small "window". The window would only be complete if I put some sort of beam along the top, fastening it to the top of the 2x4s - essentially beginning the frame for a corner pergola if I ever decided to put some diagonal shade bars in for a roof. I am having difficulty with what size the beam along the top should be. All pergola examples that I can find use 4x4 or 6x6 posts in the corners and I have 2 vertical 2x4s that actually have a gap between them from where the lattice is making for an odd measurement that is bigger that a typical 4x4 post but smaller than a 6x6.

Does anyone have some ideas on what the top beams could be? Should I pair up two 2x4s and put them on their sides across the top, lining them up with the vertical 2x4s and just leave the gap between them? Will 2x4s look to "wimpy"? Would two 2x6s turned on their sides look better or would they overwhelm the vertical 2x4s? Anyone have any photos or ideas? The reference photo of an example from elsewhere that I keep coming back to is below. I would love to do something similar, but that would still look good without using 4x4 posts. Any help is greatly appreciated! Thanks!