Flooring over unwanted spiral stairs opening

[kotbegemot]

Hi folks. Grateful for advice on how to reinstall the floor once I've got rid of this spiral staircase please? It's the structural detail I'm most interested in..

The opening is 120cm in diameter. The aperture has been formed in an octagon, in which two sides are constituted by the main floor joists, 130cm apart (lighter wood in the pictures below). The other six sides (darker wood) are fixed to these two joists somehow, and probably to a central joist that was cut to create the opening.

Should I be looking to attach a joist between the two original main joists (i.e. at right angles)?

Or should the new joist follow the same direction as the originals?

What method should I use to fix the new joist in place?

What regulations should I read up on and where can I find them? (I worry the previous owner skipped this bit).

 

[kotbegemot]

Adding this to try and clarify. Yellow lines - original joists, red lines additional joists to form opening.

 

[freddiemercurystwin]

Assuming the yellow ones are the original joists they will (or should) be double joists, then perpendicular to those either side of the opening there would be another pair of trimmers that pick up the ends of the joists that had to be cut to form the opening.

But how do you know the yellow ones are the original joists and not the trimmers? Do the floor boards run perpendicular to the yellow joists?

If it was done correctly it should have been done like this:

 

[kotbegemot]

Thanks for your response.

To be honest, I don't know if the lighter joists are original - I just made that assumption because there were two of them, suggesting that the other six sides were the new additions. This stairwell was added some time after the house was built.

If I understood correctly, if this was done properly, all of the visible beams in the pictures would have been added to the original floor joists for strength?

The MDF floor boards run perpendicular to the yellow joists.

 

[freddiemercurystwin]

That would be a reasonable assumption, that the yellow joists are the trimmers but you cannot assume anything unfortunately. You'll need to cut back some of those floor boards in anycase so that the ends start/stop on top of a joist so you'll be able to find out that way for sure.

Infilling is fairly simple its just a case of finding some new joists that match the height of your originals and fixing them in place with suitable hangers.

But I would start by trimming back some of the chipboard boards going as far back as far as you need to until you meet the trimmers, or the main joists, you'll have to remove the red bits too and also the little vertical battens that form the curve.

BTW the floor boards are chipboard not MDF.

 

[kotbegemot]

Thank you. That all sounds sensible and within my competence! I'm going to have a crack in August when funds permit. I'll post an update in due course.

 

[endecotp]

when funds permit.

Are you going to try to sell the stair? It should be worth something - if you can find the right buyer!

 

[kotbegemot]

Yup. That's the plan. Located in rural Scotland though, so might take a while for a buyer to come along!