My mum just bought a old HDB flat and is currently doing renovation. As you can see in the picture, the old aircon in the master bedroom has been removed and we are left with a hole. The ID said he will just cover up with wooden plank. But we are concerned that this is not a long term solution as rain water will seep through. Anyone know if HDB allows us to use bricks to cover up this hole ? Any inputs or suggestions greatly appreciated.