Tier 2 Furnace placement

i builded one large Furnace in my house. In the middle was a free place. But i cant make a ceiling on top of my building. Is this a bug ???

They dont really want you to put the furnace inside your house.

Then i will use small furnaces. One room with furnaces is enough for me.

build first, place furnaces after.

how much height should you allow in a room for a t2 furnace to be placed afterward? is it two stories high?

You cant make a ceiling over a tier 2 furnace.

Yes you can, first build, then place furnace.

how much horizontal and vertical clearance should the furnace room have?

2x2x2

If you build a large furnace on the ground and a structure around it, you need to build at least 3 floors up from that before you can actually cover it up. Otherwise, you’re stuck with an open roof.