How big should I build my next grow room for 10 plants?

Its going to be a 10 plants in 3 gallon pots each with a 1000watt hps light and I wanna make room for fans and branching out and all that... How big should all the measurements be?

10 plants, 1 light........ not possible unless SOG, not enough coverage. Go 2 x 600w and you will be sweet with 10 plants. Actual floor space for plants 8ft x 4ft then add any working space. Also consider seperate veg and drying area, these are things you will kick yourself for if you dont do at the beggining. good luck.

Iv grew 8 plants at a time with this light what could 2 more do?

well if you already have your hood and your not up for change than you should build your room around the hood footprint @ highest point.. Average footprint would be like 4x4.. Im setting up a raptor hood in that size space. lol... Im just working with what material and space I have..
start a journal it sounds like fun

u can do alot with 1100watts and an adjust-A-wing and a diffuser and a sick bulb u can get 4x8+ as long as u rotate your plants which ur supposed to do anyway. Continuous grows ftw though of coarse 3 gallons so 10 3ft plants can be done.
but I admit I really would benefit from another light. actually 3 400WATTS trump 2 600 everyone knows that hortilux blues bro. luckily gonna greenhouse and cooler temps next year.
but heat is a pain too with a 1000