The joy of small computer rooms...
Figure your power and then double that. Then double it again.
If you have 800 mm deep racks, you can't put modern servers in them.
If you have 1.2 m deep racks, you need 1.2 meters in front of them if you expect to put rack mount servers in them. 600 mm deep racks are only useful for cable termination and sometimes not even that.
You need at least 600 mm on all other sides.
Raised floors are cool but they come in 600 mm x 600 mm (or 2 ft x 2 ft) and you can't cut them and be useful in a small computer room. That means you need at least 5 tiles in a line per rack (600 mm behind, 1200 for the rack, 1200 in the front to load the rack). You need 600 mm on both sides and you better figure on two racks. For 7x5 full tiles is the minimum. Builders cut floor tiles to fit the room, not the other way around so either you have some sort of extra stuff around the edge or your tiles have to go in like a jigsaw puzzle where every piece is rectangular and white.
You need 1 kW of cooling for each kW of servers. A reasonable split system can do 6 kW of cooling but you also need two for redundancy.
Your UPS and cheap generator won't run a 6kW air conditioner but it can run a 2.5kW one.
We have 2 racks that each take about 1 kW and we have two 6 kW A/C and two telco grade 48V systems hooked to 16 truck sized deep cycle batteries. We can run 8 hours (except for that A/C thing) and the solar can extend that for another 4 (except for that A/C thing with a more effecient sun heating load bit)
You want LED lights hooked to the UPS. You want a phone in the room assuming tbe PBX is there too and you might want a way to power if assuming the POE switch isn't in the UPS.
A rack can weight 2 tons. Make sure the floor can cope. Even if it isn't that heavy, it can put massive loads in very small areas on a floor.
Make sure you have the door on the alarm and put in smoke detector in the room.
Did I mention that you need to double your planned power? And then double it again?