Tricky to attach post to stair railing in flooring

[Pgam]

The best way to attach a post to a stair railing is to secure it under the floor in the joist, I understand, and I've followed that approach while building the railing. But I've reached a Catch-22 now when it's time to install it. The base rail is intended to rest on the floor, but if the floor is already in place, I can't reach to screw the post in!? I've delayed finishing the floor because of this.

I thought maybe I could fit the floorboard in afterwards if I measure it perfectly... But it feels like there's a big potential to fail. The floor is made of solid tongue-and-groove pine, and it's laid parallel to the railing. In hindsight, it seems it would have been smarter to start the flooring installation at the railing, but I've done the opposite.

I'm starting to lean towards placing the base rail slightly below floor level and laying the last floorboard against the base rail instead of under it...

Does anyone have a good solution or tips along the way?

 

[Oldboy]

Isn't it just a matter of mounting the post in the joist, laying down the floorboards, and then mounting the underlag?

 

[Pgam]

Isn't it just a matter of mounting the post in the floor framework, placing the floorboards, and then mounting the ledger?

Well, it wasn't built like that, the ledger is mortised into the post, and there's no room to mortise it back in once it's mounted (not a through mortise but only on one side, if you know what I mean), so I don't see a way to do it like that, but maybe there's something I've missed...

 

[BengtH]

Image?

 

[Pgam]

Image where the post should be attached (in the corner where the felt is folded up)


overview


drawing of the railing, didn't have a picture of it at the moment. Might be able to get one soon.

 

[Oldboy]

Ok.
If I interpret the drawing correctly, is the sleeper 45mm high?

If so, the first two alternatives that come to mind are, as you yourself suggested, to lay the sleeper directly on the joist, and to minimize or completely remove the tenon so that it is possible to retrofit the sleeper.

If the sleeper is 45mm high and the floorboards are <30mm thick, there is a possibility to add a molding if the gap for some reason becomes uneven or needs to be a few mm wide, e.g., due to floor mounting with tongue and groove. (When mounting directly on the joist.)

 

[richardtenggren]

Can't you run with a loose tenon, by
modifying the support with a mortise and making the mortise in the post through?