Omar Cummings came within inches of breaking the deadlock when he latched on to a pass from Giles Barnes. The forward chested the ball and hit it first time on the volley, but his effort clattered off the crossbar.
Montreal took advantage of this good fortune when McInerney headed them ahead in the 42nd minute as he timed his run to perfection and nodded Eric Miller's cross over Hall and into the net.
After the break, Hall kept Houston in the game when he made a good save to tip Marco di Vaio's close-range shot over the bar after the Italian had run the length of the field to raid into the box.
The home side doubled their lead as McInerney got his second of the game in spectacular fashion when he directed Justin Mapp's cross from the right over Hall and into the top corner.
Di Vaio sealed the win for the Impact as he tapped home from close range into an empty net after Hall could only parry a powerful shot from Andres Romero into his path.