just wondered if wooden structurs would support say 4 stories or so

Yes you can

It depends where you build really, I got up to 3 stories (approx) at Sanctuary but ran out of materials, need to get some more. I'm yet to hit the ceiling but I don't want that to happen.

Depends on the settlement location, though. Hangman's Alley CAN'T handle 4 stories.

I saw someone build a staircase that was 10 stories. No building around it though. Just the staircase.

Depends on location. Some locations have a hight limit. Like hangman's ally.

But I have a few 5 story buildings around other locations. Just have a play and see what you can make...

I have 11 or 12 stories on some. In Greywater and another settlement, I built them all the way up to the highway overpass bridges and attached them. It's way to large to be useful but its fun.

I've build about 7 stories at the Starlight Drive In..... ive seen up to 10 but it was really small.

oh i bet he's trying to build a stairway to heaven to talk to his dead friend about the candy coupons.

Don't forget to save often when building at hight. One accidental store floor in workshop and that's quite a fall to your death and restart all the building again...

I think I also saw a mod that extended the skybox limit for settlements by a lot

Yes...my shackmansion at Sanctuary is four stories...can't go any higher as I've hit Sanctuary's build limit.