Other mistake: As this is complicated you have to look for it very carefully. As Nell first enters Hill House she hears the sound of Mrs. Dudley that we later know comes from the kitchen. She follows the sound, going through a door on the right that leads to a long hallway. What is wrong here is that by the direction of the hallway, it should be passing right through the dining room. If not it should be passing beside it, which is not possible since we see that the dining room has tall windows to the outside. The other option is that the kitchen should be before the dining room, which is also impossible, since at dinner, Theo comes from the opposite direction and both Nell and Ms. Dudley come from the kitchen, through a door on the left side of the dining room, right beside the long stairs.
Visible crew/equipment: As Nell turns around to see all the lights in the house turning on, we see in the background, the rest of the group trying to save Luke, but at the very beginning of the shot, you see a blue light quickly flicker behind Nell, that couldn't have been the cars lights, which only means that was the crew's lights.
Continuity mistake: Luke's hair changes length and style throughout the film. It starts off quite long at the back and sides over his ears then after Nell and Theo hear noises on the first night and Luke comes to the door to see what's happening its been cut, coloured and layered then when he's speaking to Liam Neeson a bit later on it's long again.
Factual error: The original and remake are both set in America, yet the outside shot of the flat at the start of the remake is in England. It is blatantly a 1920's London council flat, probably one of those in The Borough. The original 1962 film also contained British background details. Was this intended as homage to the original?
Revealing mistake: When Luke tries to ram the gate with his car, a huge piece of spear-point wrought iron falls and impacts the roof of his vehicle. As the others rush to rescue Luke from the car, we can see the wrought-iron spear points flexing and bending, because they are made of rubber.