Am restoring part of upper deck of RCL2259. Have the cork 3mm sheets for under the seats and Mitch at the association has sorted some slats for us, (thanks Mitch and Andrew Morgan who came to visit),. My question is, what goes between the slats? Our bus was a tour bus so the floor is made of this lino waterproof stuff, which is green/blue. ( I have stripped back the sides to expose the aluminum, which looks great

Want it to look good. Should I be painting the floor before laying the gangway slats, and if so, what colour would you recommend. Is there a standard fort this?

or Should thin cork be under the slats as well?

Advice gratefully received.

My bus number (if any): RCL2259

If it's not going to be open topped it's very simple.
Nothing goes between the slats. However, RCL's and production RMLs have matting not single slats. Have a look on Flickr at the RML 2323 page, they show the upper saloon floor. It's no different from the lower saloon actually.

If you are having to use single slats, clean off the floor area completely to bare metal, apply a coat of Bostik all over the centre aisle, allow to go dry. Apply Bostick to slats, fit in place.

Edit
Forgot to mention, if you are using single slats, the outside ones have a different profile, thy are chamfered to meet matting.

My bus number (if any): RTL 960, RMC 1458 RM 1585, (M 961, M 271 - both sold) and several RTs

I'm sure that RCLs had smooth flooring throughout although it was a treadmaster product..
If the bus is open top you will need to seal all the joints and then put a tin sealing membrane over the whole floor area before putting treadmaster down.
Water ingress and treadmaster are not good and water trapped in the alloy floor is a corrosion nightmare.
Water ingress has done for a lot of the original open topper conversions and the sealed waterproof flooring was not done for cosmetic reasons.

You are right Jack RCLs had slat thickness mats in the centre, but Robert said he had been supplied with slats. If open top will certainly need some weatherproofing. If you think RMs are corroded being open topped you should see what an RT looks like in the destination blind areas front and back.

My bus number (if any): RTL 960, RMC 1458 RM 1585, (M 961, M 271 - both sold) and several RTs

Robert is creating the "look" of a Routemaster and I believe is happy with the slats.

If you look on page 99 of the Haynes Routemaster Bus Enthusiasts' Manual, then you will find two photos of newly laid Treadmaster in my own RM.

My bus number (if any): RM1368

Well then, to answer his question nothing goes between the slats 4except the coat of Bostik black put down over the whole area and allowed to go off.

My bus number (if any): RTL 960, RMC 1458 RM 1585, (M 961, M 271 - both sold) and several RTs