Nhut, you’re toast. No pre-agreement, no obligation to pay you. I’ve read adjudicators orders saying just this. Arrangements and payments need be discussed beforehand, but that said you might still present them a list of what you’ve done and your fair price, and get a professional quote to compare the difference which should be plenty (as they have gear and insurances etc that you don’t). I know it seems just but the committee really do need things done in the right order as they have limited scope to spend money on behalf of all owners. I got busy myself doing a shopping list of things my mob never thought needed doing then one day I presented details and bills. I’d saved them thousands of dollars and helped the place look less bedraggled then presented a detailed bill seeking reimbursement. Unbelievably they short paid it and then claimed my doing so was damaging common property! Unreal. I thought to undo the work where I could but thought my own efforts addressed things they wouldn’t do so I just moved on. Perhaps you might too.