"我哋用嚟放架罉嘅工棚" is grammatical correct. But I would suggest the use of 擠 instead of 放, and 雜物房 instead of 工棚.
雜物房 might not be the appropriate term, but 工棚 is not used in Cantonese.
雜物房 might not be the appropriate term, but 工棚 is not used in Cantonese.
