How to make the floor for 2nd storey?

[Hrw-Amen]

I am currently making a house. It is the first 'big' thing I have built since my return to LEGO after many years. I have made the basic structure of the ground floor and am putting in some details. I note from looking on here that people use flat surfaced tiles to enable the upper floors to be easily removed and I can see the sence in that. My question is what do you use to make the floor of the second/third and so on, storey. Do you use another base plate and somehow hide the fact by putting a skirt around it, or do you use ordinary plates, (I have only found these in smaller sizes.) and join several together to get the right size, or am I missing something and it is done in a totally different way? I was going to use the smaller plates and overlap them, but then I thought the floor/ceilings would be so thick. I am not sure how to proceed?

[Rick]

Most follow the modular buildings as inspiration. You can have a look at the building instructions of Cafe Corner (set number 10182), Market Street (10190), Green Grocer (10185), Fire Brigade (10197), and Grand Emporium (10211) on LEGO's building instructions website. The instructions are also accessible via Brickset (click the icon below the set number).

But to answer your question: they use regular big plates connected by 2xX and 1xX plates from below.

[F0NIX]

I also get the inspirations from the CC-style buildings. And I use a "sandwich" type structure like in real buildings. Plates as ceiling, 1x bricks between and plates on top of that again. The bottom plates could be light colored plates, I like to use white to emulate real ceiling plates.

You could also use two layers of plates, but that would not make it as strong.

[snaillad]

Baseplates are thinner than normal plates s perhaps it will not 'sit' right and may be more difficult to get it to stay in place, sometimes I use a 'stepped' effect for the bottom of the upstairs floor. I use a 'Z' shape with a plate on the top and bottom facing opposite ways with a normal height brick inbetween but only on the front of the building so it sites flush. There is no need to use too many plates but if you are short on surface area reinforce them from underneath with a 2x8 flat plate etc. I would echo what has been said about checking out the instructions on brickset for the modular build sets. Maybe it will help :)

[gotoAndLego]

Traditionally the floor is two plates think. The first is what you want to see and under that is bracing. The bracing can be ugly because you never see it.

[alois]

A baseplate also doesn't work when you want to have stairs going through the floor. I mainly use plates, I assemble the in the right shape and then put 2-stud wide plates under them to hold the whole thing together.

I always try to keep the lowest layer one stud apart from the outer rim of the floor, in that way they fit between the walls of the first floor and keep the second floor in its place.