Does anyone know what horror movie I am trying to remember based on this description?

this movie, late 70's or early 80's I think, had these people trying to renovate a building like an old hospital or something. They get trapped there and one by one die, until this one couple is left and they find the devil(looking just like a mischievous man) in a trapdoored room under the place and they stab him(?) or something and finally escape. Two notably scenes involve the main male character trying to use a saw on a locked door and he is "overtaken" by the force of the house and cuts into his own hand. The other is when a different man manages to get outside the house but is immediately sucked into the ground and never seen again. Please help me,, this is getting to be annoying that I can't remember this! thank you all!!!